Table of contents

The 22nd International Conference on Spectral Line Shapes (ICSLS) was convened at The University of Tennessee Space Institute (UTSI) at Tullahoma, Tennessee, USA, during June 1 to 6, 2014. A variety of topics of interest to the line shape community were addressed during invited and contributed oral and poster presentations. General categories of the ICSLS 2014 scientific contents included Astrophysics, Biomedical Physics, High and Low Temperature Plasma Physics, Magnetic Fusion Physics, Neutrals Atomic–Molecular–Optical (AMO) Physics, and Applied Physics. Research interests at UTSI and at the Center for Laser Applications (CLA) focus on Applied Physics and Plasma Physics areas such as laser–induced breakdown spectroscopy, spectroscopy with ultra–short light pulses, combustion diagnostics, to name a few. Consequently, the presentations during the conference addressed a variety of these topics.

Attendance at the conference included researchers from North America, Africa, Asia and Europe, with an international representation showing 250 authors and co–authors with over 25 different citizenships, and 100 participants at the Conference. Figure 1 shows a photo of Conference attendees. The schedule included 82 contributions, 41 oral and 41 poster presentations. The 29 invited, 12 contributed oral and 41 contributed poster presentations were selected following communication with the international organizing committee members. A smart phone ''app'' was also utilized, thanks to Elsevier, to communicate electronic versions of the posters during the conference. Special thanks go to the members of the international and local committees for their work in organizing the 22nd ICSLS. In addition, thank you notes also go to the peer reviewers for the proceedings. Following the success of the IOP: Journal of Physics Conference Series selected for the 21st ICSLS publication, the proceedings papers report ongoing research activities. Papers submitted amount to 68 in number, or 83% of the 82 papers contributed to the 22nd ICSLS conference will be published in the IOP: Journal of Physics proceedings.

The Executive Director of the University of Tennessee Space Institute welcomed all participants of the Conference on the first day of the technical sessions on Monday June 2, 2014. This welcome address is also included in the conference series publication, especially important for Physics and Engineering research at UTSI is the concurrent 50–year celebration of the Institute in 2014. Informal welcome occurred on Sunday June 1, 2014, and various social activities included a tour to the Jack Daniel's distillery in Lynchburg, Tennessee, followed by the conference dinner.

The international scientific committee met to look into various aspects of the ICSLS and future role of this conference for the spectral line shape community. The next meeting locations have been discussed, including the scheduling of the next 23rd conference in Torun, Poland, in June of 2016. Further meeting locations include hosting the conference in Egypt in 2018, possibly in Luxor, Egypt. Communication regarding the 24th ICSLS in 2020 included mentioning of scheduling the Conference to occur in Dublin, Ireland.

Clearly, there is a wealth of interest in continuing the long standing tradition of communicating spectral signatures and line shapes at the biannual ICSLS meetings. The 22nd International Conference on Spectral Line Shapes was supported by the Institute of Physics, the University of Tennessee Space Institute, the Center for Laser Applications, the Quantel Laser company, and by Elsevier. On behalf of the organizing committee, I greatly appreciate the support.

A welcome from Robert N. Moore, PhD Executive Director and Professor of The University of Tennessee Space Institute can be found in the pdf.

Minutes of the International Program Committee, 22nd ICSLS can be found in the pdf.

All papers published in this volume of Journal of Physics: Conference Series have been peer reviewed through processes administered by the proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

The astrophysical importance of Mg, together with its unique range of spectral features in late-type stars, plus its relative simplicity from an atomic physics point of view, makes it a prime target and test bed for detailed ab initio non-local thermodynamic equilibrium (NLTE) modelling in stellar atmospheres. In this paper, we present example first results for calculations of NLTE Mg line based on a new model atom with significant improvements in the collision data for neutral Mg. We perform calculations for excitation of the lower-lying levels due to electron impacts using the R-matrix method. Recent data for excitation and charge transfer due to hydrogen atom impacts involving low-lying levels are now employed. Further, we have made efforts to use physically-motivated methods for calculating radiative and collisional data involving Rydberg states. The results are compared with observed spectra and the impact of the new calculations briefly explored.

It is widely accepted that active galactic nuclei (AGN) are hosting a supermassive black hole in their center. The supermassive black hole is actively fueled by surrounding gas through an accretion disk, which produces a broad band continuum (from X-ray to radio emission). The hard photons from the accretion disk create the photoionized plasma around the central black hole, which emits a number of broad emission lines. Therefore, one of the signatures of the strong activity in galaxies is the emission of the broad spectral lines (line widths of several 1000 km/s), which are seen only in a fraction of AGN, so called Type 1 AGN. These broad emission lines often show very complex line profiles, usually strongly variable in time. Here we will describe the basic properties of the broad emission lines and how can we use them to derive the properties of the central supermassive black hole, i.e., the mass and spin, or see signatures of supermassive binary black holes.

Quantum mechanical and classical methods for theoretical analysis of the emission spectrum due to radiative association are presented. Quantum mechanical perturbation theory is employed to obtain the spectra when the diatomic molecule HF forms by transitions within the electronic ground state and when it forms by transitions between two electronic states. We contrast these spectra with each other. The former peaks in the infrared, while the latter peaks in the ultraviolet. The classical spectrum, which concerns transitions within the electronic ground state, is also calculated and found to favorably compare with that from quantum mechanical perturbation theory. The emission stemming from resonance mediated radiative association is also discussed.

The Two-Body Dirac equations of constraint dynamics applied to QED yields an exact Sommerfeld-like solution for the spectrum of ¹Jj singlet positronium states which agrees with standard perturbative results through order α⁴. At short distance the radial part of the wave function u = rψ has two solutions with probabilities near the origin behaving like . For J ≠ 0 only the first sign is allowable but both signs for J = 0 are well behaved. The first sign in that case corresponds to ordinary positronium (with a binding energy of about 6.8 eV). The second sign corresponds to a new positronium state with a binding energy of about 300 keV and a root-mean-square radius on the order of a Compton wavelength. The ordinary 1S positronium state decays into this new 1S state by two photon emission with c.m. energy of about 300 keV. The peculiar 1S state then annihilates promptly into two photons with c.m. energy of about 700 keV. Thus the existence of this new positronium state would be a distinctive 4 photon decay signature of ordinary singlet positronium.

More and more cold interstellar molecules are being discovered, the majority of them being organic. Perhaps it is time to consider the numerous small molecules that also await observation. We report progress in tabulating symmetric-stretch vibration frequencies for neutral main-group ground-state triatomic molecules, formed from period-2 atoms, which are not yet studied.

Traces of heavy metals in cool DZ white dwarf stars may be attributed to the accretion of circumstellar dust thought to originate from tidal disruption of rocky parent bodies. Spectra of such stars therefore provide a unique opportunity to study the composition of extrasolar planetary systems. The determination of metal abundances from stellar spectra depends on stellar atmospheric parameters and an accurate prior knowledge of the collision broadening of the line profiles by the most common constituents of the stellar atmosphere. For this purpose, we present theoretical absorption spectra of Na and Ca⁺ broadened by He for the conditions prevailing in cool white dwarfs.

Sedentary lifestyle of human beings has resulted in various diseases and in turn we require a potential tool that can be used to address various issues related to human health. Laser Induced Breakdown Spectroscopy (LIBS) is one such potential optical analytical tool that has become quite popular because of its distinctive features that include applicability to any type/phase of samples with almost no sample preparation. Several reports are available that discusses the capabilities of LIBS, suitable for various applications in different branches of science which cannot be addressed by traditional analytical methods but only few reports are available for the medical applications of LIBS. In the present work, LIBS has been implemented to understand the role of various elements in the formation of gallstones (formed under the empyema and mucocele state of gallbladder) samples along with patient history that were collected from Purvancal region of Uttar Pradesh, India. The occurrence statistics of gallstones under the present study reveal higher occurrence of gallstones in female patients. The gallstone occurrence was found more prevalent for those male patients who were having the habit of either tobacco chewing, smoking or drinking alcohols. This work further reports in-situ LIBS study of deciduous tooth and in-vivo LIBS study of human nail.

In biological phenomena there are indications that within the long pulse-length of the action potential on millisecond scale, there is additional ultrashort perturbation encoding that provides the brain with detailed information about the origin (location) and physiological characteristics. The objective is to identify the mechanism-of-action providing the potential for encoding in biological signal propagation. The actual molecular processes involved in the initiation of the action potential have been identified to be in the femtosecond and pico-second scale. The depolarization process of the cellular membrane itself, leading to the onset of the actionpotential that is transmitted to the brain, however is in the millisecond timeframe. One example of the femtosecond chemical interaction is the photoresponse of bacteriorhodopsin. No clear indication for the spatial encoding has so far been verified. Further research will be required on a cellular signal analysis level to confirm or deny the spatial and physiological encoding in the signal wave-trains of intercellular communications and sensory stimuli. The pathological encoding process for cardiac depolarization is however very pronounced and validated, however this electro-chemical process is in the millisecond amplitude and frequency modulation spectrum.

The opacity is an important issue in the knowledge of radiative properties of ICF and astrophysical plasmas. In this work we present the opacity of dopants embedded in the ablator of some ICF capsules. The silicon is used as dopant and we are interested in C+Si mixtures. We have used two methods to calculate the opacity of C+Si. The first one involves a detailed line shape calculation in which the atomic database is provided by a MCDF code. The lineshape code PPP is then adapted to the calculation of opacity profiles. Almost all spectral broadening effects, including Zeeman splitting and Stark effect, are taken into account. This method is able to provide accurate opacity spectra but becomes rapidly prohibitive when the number of lines is large. To account for many ionic stages and thousands of lines, a second method -hybrid method- is prefered. This method combines detailed-line and statistical calculations. In the spectral regions where the lines are sufficiently separated and the number of radiative transitions is moderate, the hybrid method performs detailed calculations. When the number of transitions is very large and most of them merge in broad structures due to line broadening, the hybrid method performs statistical calculations.

An accurate knowledge of atomic collision processes is important for a better understanding of many astrophysical and laboratory plasmas. Collision databases which contain electron-impact excitation, ionization, and recombination cross sections and temperature dependent rate coefficients have been constructed using perturbative distorted-wave methods and non-perturbative R-matrix pseudo-states and time-dependent close-coupling methods. We present recent atomic collision results.

We report calculations of hydrogen line shapes in tokamak edge plasma conditions. A special emphasis is put on the motional Stark effect that arises due to the electric field × present in the frame of reference of an atom moving at a velocity . The statistical repartition of the velocities results in a broadening of the lines, which can be significant if the upper level of the transition under consideration is high. Applications to Balmer lines are shown here.

A parameterization of the Balmer-alpha spectral line shape asymmetry in the tokamak scrape-off layer (SOL) plasmas is suggested, which describes the contribution of nonMaxwellian components of the neutral atom velocity distribution function. Parameterization is needed for a fast-routine interpretation of high-resolution spectroscopy data and should be incorporated into the algorithms for the recovery of hydrogen neutral atom parameters in the SOL. We illustrate the efficiency of the parameterization on the example of spectral data calculated using the predictive modeling of the International Thermonuclear Experimental Reactor (ITER) tokamak operation.

The temperature dependence of the Cd line absorption profile at 326.1nm perturbed by inert gases (Xe, Kr, Ar, Ne and He) has been carefully studied over a wide spectral range in both blue and red wings using a high-resolution double-beam spectrometer. The atomic densities of inert gases (N_gas) and cadmium (N_Cd) was sufficient to study the wing of the Cd line at 326.1nm. The temperature dependence of the studied line profile was analyzed in the framework of the quasi-static theory. The van der Waals coefficient differences (ΔC₆⁰ and ΔC₆¹) between the ground X0⁺ state and the two excited states A³0⁺ and B³1 were obtained from the near red wing profile using Kuhn's law. All the results of the well depths with their positions for the ground (X0+), and the excited (³1, ³0+) were determined. The obtained results are compared with the corresponding theoretical and experimental molecular beam experiments results.

The vector interference dip most clearly seen in the fundamental collision-induced band of H₂ and H₂ mixtures at densities upward of 20amagat, is well known to persist at densities down to 1 amagat. However, At lower densities it is not seen. Lewis and Herman gave a theory of this infilling. In this work we approach the problem from the simple statistical models for collision-induced absorption introduced by Lewis in 2000 and subsequently much elaborated. The statistical model shows infilling, but rather than a uniformly infilling dip the model shows a small central peak forming in the dip, then broadening with increasing amplitude.

A short review of recent achievements in high-precision cavity enhanced absorption spectroscopy is presented. Actual challenges and development paths in modern line shape study are indicated and discussed. The importance of identification and quantification of systematic instrumental errors affecting the measured line shape is highlighted. New, alternative measurement methods based on cavity enhanced spectroscopy are proposed.

Frequency- and polarization-resolved degenerate resonant four-wave mixing is used for the first time to study the rotational anisotropy of the OH radicals produced by photolysis of H₂O₂ by a plane-polarized laser radiation at 266 nm. For that, a flexible polarization setup is designed to directly isolate the rotationally anisotropic signals in the A²Σ⁺ – X²Π(0, 0) OH vibronic band. The results are quantitatively interpreted by using the line-space approach and accounting for all possible correlations between the electric field E_D of the photolysis laser, the recoil velocity v and the angular momentum J of nascent particles. In so doing, the resonance amplitudes are decoupled into products of the polarization factors, the Doppler-broadened profiles and the Einstein B-coefficients. The anisotropic signals have characteristic shapes of well resolved Doppler doublets providing a direct evidence of translational helicity of the nascent OH radicals, a hitherto exprementally inaccessible key characteristic of the photodissociation path.

The recording of Raman spectra for many molecules in air at room temperature is difficult or impossible as a result of sample degradation which is due to a combination of laser heating and oxidation. Often nitrogen gas is applied over the sample in an attempt to reduce oxidation. Also, the samples are sometimes cooled to reduce ro-vibrational "hot bands" and enhance the spectra. We have found great utility in recording Raman spectroscopy of samples under liquid nitrogen, a technique we call RUN. The RUN spectra show much higher resolution as a result of ro-vibrational cooling and in some cases cooling produces only the lowest energy conformer of the molecular ensemble further simplifying the spectra. A very sharp Raman peak at 2327.0 cm⁻¹, due to liquid nitrogen, also serves as a convenient wavelength calibration. We also demonstrate the ability to clearly delineate the lattice modes for naphthalene and benzene crystals.

The H + H⁻ → H + H + ℏω,H + H⁻ + ℏω → H + H + e reactions give examples of bound-bound and bound-free electron transitions in the H + H⁻ quasimolecules temporally formed during collisions. The present work is aimed at the calculations of spectral profiles produced in the reactions.

Line strengths and line shape parameters have been measured for a single absorption transition of both hydrogen chloride and hydrogen fluoride gases. These parameters were determined from spectral absorbance measurements over a range of temperatures and pressures using single-mode laser diodes as the laser sources. The measured parameters are compared to values reported in scientific literature. Significant differences are observed that will impact spectroscopic measurements of species concentrations, temperature, and pressure.

The consistent relativistic energy approach to atoms in a strong realistic laser field, based on the Gell-Mann and Low S-matrix formalism, is applied in the study of resonant multiphoton ionization of krypton by intense uv laser radiation and for the computation of the resonance shift and width in krypton. The approach to the treatment of the multiphoton resonances in nuclei is outlined for the ⁵⁷Fe nucleus.

Nanoparticles of magnetic crystals below a critical size are single domain and exhibit superparamagnetism. If there are N atoms or molecules with magnetic moment μ in each particle, the magnetic moment of the particle is Nν. At high temperatures the thermal fluctuations of the magnetic moments give an ensemble average moment of zero and the Mössbauer spectrum is a single line. As the temperature, T, is lowered the fluctuations slow down and the sample acquires a magnetization and the Mossbauer line broadens and eventually shows magnetic hyperfine splitting. We have observed ⁵⁷Fe line broadening in nanoparticles of ferrimagnetic Fe₃O₄ with diameters of 5.3 and 10.6 nm. The results have been analyzed using the motional narrowing equation familiar in nuclear magnetic resonance to determine the superparamagnetic fluctuation time and magnetic anisotropy.

We present analysis of the R7 Q8 O₂ B-band rovibronic transition measured with ultra-high signal-to-noise ratio by Pound-Drever-Hall-locked frequency-stabilized cavity-ring- down spectroscopy. For line-shape calculations ab intio in spirt approach was used based on numerical solution of the proper transport/relaxation equation. Consequences for spectroscopic determination of the Boltzmann constant as well as precise determination of the line position in the Doppler limited spectroscopy are indicated.

We report the use of a digital lock to measure the line profile and center frequency of rubidium 5S-7S two-photon transitions with a cw laser referenced to an optical frequency comb. The narrow, two-photon transition, 5S-7S (760 nm), insensitive to first-order in a magnetic field, is a promising candidate for frequency reference.

New approaches to cavity enhanced absorption spectroscopy are presented. They are based on precise measurements of shape of cavity modes broadened and shifted in the vicinity of the absorber placed inside the high-finesse cavity. The usefulness of both techniques to accurate line-shape study is demonstrated on an example of a weak (3 ← 0) ¹³C¹⁶O transition.

The consistent quantum approach to calculating the electron-nuclear γ transition spectra (a set of the vibration-rotational satellites in a molecule) of a nucleus in polyatomic molecules is used to determine accurate data of the vibration-nuclear transition probabilities. We present results for emission and absorption γ-spectra of nucleus ¹⁹¹Ir (E⁽⁰⁾_γ= 82 keV) in the molecule of IrO₄.

New relativistic approach, based on the relativistic many-body perturbation theory using optimized wave functions sets, is applied to calculate the hyper fine structure collision shift for rubidium atom in atmosphere of the helium inert gas. Data for the collisional shifts of the Rb-He system are presented and compared with data available in the literature.

We report on a theoretical study of the H₂-He and H₂-Ar pair trace-polarizability and the corresponding isotropic Raman spectra. The conventional quantum mechanical approach for calculations of interaction-induced spectra, which is based on an isotropic interaction potential, is employed. This is compared with a close-coupling approach, which allows for inclusion of the full, anisotropic potential. It is established that the anisotropy of the potential plays a minor role for these spectra. The computed isotropic collision-induced Raman intensity, which is due to dissimilar pairs in H₂-He and H₂-Ar gas mixtures, is comparable to the intensities due to similar pairs (H₂-H₂, He-He, and Ar-Ar), which have been studied previously.

Results of line-shape measurements of self- and N2-broadened P9 P9 transition of the oxygen B band are presented. Spectra were acquired using the optical frequency comb- assisted Pound-Drever-Hall-locked frequency-stabilized cavity ring-down spectrometer (PDH- locked FS-CRDS). In the line-shape analysis the line narrowing described by Dicke narrowing or/and the speed dependence of collisional broadening were taken into account. The multispectrum fitting technique was used to minimize numerical correlations between line-shape parameters. Collisional broadening and shifting coefficients are reported with sub-percent uncertainties. Influence of the spectral line-shape model used in data analysis on determined line intensities and collisional broadening is discussed.

The study is devoted to the theoretical analysis of ultrashort electromagnetic pulses (USP) absorption on broadened dipole transitions. Calculations are made in the frame of perturbation theory with the use of the basic formula for energy absorbed during all time of the action of USP on dipole transition. Dependences of absorbed energy upon pulse duration and carrier frequency are obtained and analyzed for different types of spectral line shape and USP parameters.

The review covers theoretical and experimental studies of two kinds of dips (local depressions) in spectral line profiles emitted by plasmas: Langmuir-wave-caused dips (L-dips) and charge-exchange-caused dips (X-dips). Positions of L-dips (relative to the unperturbed wavelength of a spectral line) scale with the electron density N_e roughly as N_e^1/2, while positions of X-dips are almost independent of N_e. L-dips and X-dips phenomena are interesting and important both fundamentally and practically. The fundamental interest is due to a rich physics behind each of these phenomena. As for important practical applications, they are as follows. Observation of L-dips constitutes a very accurate method to measure the electron density in plasmas - the method that does not require the knowledge of the electron temperature. L-dips also allow measuring the amplitude of the electric field of Langmuir waves - the only one spectroscopic method available for this purpose. In the most recent laser plasma experiments, L-dips were found to be a spectroscopic signature of the two-plasmon decay instability. This instability causes hot-electron generation and is a critical part in laser-driven inertial confinement fusion program. As for observations of X-dips, they serve to determine rates of charge exchange between multicharged ions. This is an important reference data virtually inaccessible by other experimental methods. The rates of charge exchange are essential for magnetic fusion in tokamaks, for population inversion in the soft x-ray and VUV ranges, for ion storage devices, as well as for astrophysics (e.g., for the solar plasma and for determining the physical state of planetary nebulae).

LIBS of nanosecond pulsed Nd: YAG laser (1064 nm) produced plasma from a set of nanomaterial and bulk targets (ZnO, Fe₃O₄, Ag₂O, TiO₂, SiO₂ and Al₂O₃) is investigated at laser fluencies in the range 86 J/cm² to 2.5 J/cm². The optical emission spectra is recorded at the gate and time delay of 1 ps after the onset of the plasma in air having a constant spot size of 0.9 mm. Nanoparticle targets revealed salient enhanced spectral emission compared to their bulky counterparts. Atomic spectral lines average and integral radiance tend to decrease exponentially with laser fluence. Yet, plasma parameters measurements indicated unnoticeable variation of relative electron density and temperature. Therefore, self-absorption corrected enhanced spectral emission was plausibly attributed solely to variation in the inherent nanoparticle relative concentrations. Viable explanations were elaborated based on changes in the intrinsic physical properties of the nanomaterial under high power laser irradiation.

We present experimental studies on characterization of laser-induced plasmas relevant for the measurement of Stark widths and shifts by laser-induced breakdown spectroscopy. The selection of samples for plasma generation is investigated. It is shown that fused glass samples provide spectra with much higher line-to-background ratio for many lines of interest, compared to alloys. The influence of self-absorption on the line width is studied as a function of the concentrations of the emitting element in the sample and time of the plasma evolution. New Stark shifts for several Fe II and Ni II are measured.

In principle, an atomic or molecular spectrum would be computed as follows: Upper and lower Hamiltonians would be enumerated in a complete basis, and numerically diagonalized to give the upper and lower energy eigenvalues and eigenvectors. The transition moments for the appropriate operator, e.g., the electric dipole transition moments, would be evaluated from the eigenvectors. The vacuum wavenumbers , i.e., energy eigenvalue differences, would be found for all non-vanishing transition moments. And the line strengths for each spectral line of wavenumber would be determined as sum of the squares of the transition moments over all transitions producing the same . A line list that includes line strengths would be generated by repeating the above computations over the required range of upper and lower total angular momentum quantum numbers. The spectrum from _min to _max would be separated into a number of pixels, subsequently, the contribution of each line to each pixel is calculated using the line list. We show how this algorithm can be implemented for a diatomic spectrum if the required molecular parameters are available.

In this paper we discuss different methods of narrow spectral line shape measurements for a wide spectral range by means of high-resolution spectrometers such as the Fabry-Perot spectrometer, Zeeman spectrometer and Fourier transform spectrometer as well as a theoretical model for spectral line shape modelling and solving of the inverse task based on Tikhonov's regularization method. Special attention is devoted to the line shape measurements for the optically thin light sources filled with Hg, Ar, Xe, Kr for their use in high precision analysers for detection of heavy metals and benzene.

In this work, we utilized saturation spectroscopy to the Balmer-alpha line of atomic hydrogen in a linear magnetized plasma source with the intention of applying it to plasma diagnostics. The fine-structure of the Balmer-alpha line was observed clearly in weak magnetic field strength. Most of the peaks are assigned as transitions of the fine-structure of the Balmer-alpha line and its cross-over peaks. However, irregular cross-over peaks also observed and the population exchange among the 2s and the 2p states was suggested. Saturation spectra with Zeeman-splitting were also observed, however, the spectra became complicated with many small peaks.

Colliding plasmas are steadily gaining significance in hohlraum studies, pulsed laser deposition and laser-induced breakdown spectroscopy for a number of reasons, not least the levels of control they o.er over the properties of the slab of plasma that accumulates at the collision front, i.e. the stagnation layer. We present here some results of a time and space resolved optical-spectroscopic study of colliding plasmas formed at the front surfaces of flat and inclined Cu slab targets as a function of the wedge angle between them for angles ranging from 100° to 180° (i.e., laterally colliding plasmas). Presented here are the kinetics of atomic/ionic spatial distributions throughout the stagnation layers, both of which have been found to vary significantly with wedge angle.

Previous research regarding laser-induced breakdown spectroscopy (LIBS) of titanium normally focuses on the atomic and ionic Ti spectral transition lines. However, after a characteristic time subsequent to laser ablation, these lines are no longer discernable. During this temporal regime, the diatomic molecular transition lines of titanium monoxide (TiO) are prominent in the laser-induced plasma (LIP) emissions. TiO has long been studied in the contexts of stellar emissions, allowing for some of the molecular transition bands to be accurately computed from theory. In this research, optical emission spectroscopy (OES) of laser-induced plasma (LIP) generated by laser ablation of titanium is performed in order to infer temperature as a function of time subsequent to plasma formation. The emission spectra of the resulting ablation plume is imaged as a function of height above the sample surface. Temperatures are inferred over time delays following plasma formation ranging from 20 μs-200 μs. Computed TiO A³Φ – X³Δ, Δv = 0 transition lines are fit to spectral measurements in order to infer temperature. At t_delay = 20 μs-80 μs, the observed plume contains two luminescent regions each with a distinctly different temperature. As the plume evolves in time, the two regions combine and an overall temperature increase is observed.

We observed a laser-driven plasma soft x-ray laser (SXRL) line at the wavelength of 18.895 nm from the nickel-like molybdenum ions under the existence of external magnetic field. In this experiment, 4 mm-diameter magnetic coil driven by an electrical pulsed power supply provided the external magnetic field of 15 T along the direction of the plasma column, and we could obtain the left-handed circular and right-handed circular polarization components separately. The experimental Zeeman splitting indicated that the strength of the magnetic field was enhanced by a factor of more than 10 than that of the applied field, which implied that the compression of magnetic field occurred in the dynamics of intense laser-plasma interaction.

Theoretical studies of Rydberg autoionization resonances in spectra of lanthanides atoms (ytterbium) are carried out within the relativistic many-body perturbation theory in the generalized relativistic energy approach (Gell-Mann and Low S-matrix formalism). The accurate theoretical results on the autoionization 4f¹³[²F_7/2]6s²np[5/2]₂, 4f¹³ [²F_7/2] 6s²nf[5/2]₂ resonances energies and widths are presented and compared with experimental data, obtained by using laser polarization spectroscopy method.

In this paper, we investigate the laser-induced breakdown spectra of nitric oxide. Nitric oxide spectra are studied from laser-induced plasma emissions from plasma initiated both in laboratory air. Temperatures are inferred from the spectroscopic emissions using two methods. Spectra are fit to theoretical calculations of the diatomic spectra using the method of diatomic line strengths. For a time delay of 25 μs the temperature is found to be 6800 Kelvin. Comparisons are also provided to previously determined temperatures using a non-equilibrium air radiation fitting (NEQAIR) program.

Stark broadening and shift parameters of Cr II lines with wavelengths in the range 2000-3500 Å have been measured by laser-induced breakdown spectroscopy. The plasmas were generated from fused glass samples selected with different chromium concentrations to avoid self-absorption which would lead to distorted line profiles. The spectra have been measured at different instants of the plasma evolution from 0.6 to 3.4 gs, at which the temperature and electron density are in the ranges 12000-16300 K and (0.89-8.2) × 10¹⁷ cm⁻³, respectively. The electron density has been obtained from the Stark broadening of the H_α line.

Dual channel emission imaging of m-nitrobenzoic acid and benzoic acid was performed in order to visualize the morphology of the CN violet band emission of a TNT analogue. The CN channel was corrected for continuum emission using a simultaneously imaged background channel. Simultaneous dual channel imaging alleviated problems with shot to shot variation in the plasma morphology due to the friable substrates and showed differences between plasmas formed on the two targets.

Time-resolved spectroscopy measurements of the hydrogen alpha Balmer series line following laser-induced optical breakdown in laboratory air are designed to investigate in detail the determination of electron density from Stark-broadened spectral line shapes. Comparisons of results obtained from H_β and H_γ lines indicate higher electron density inferred from H_α early in the plasma decay, suggesting self-absorption occurs. However, detailed comparisons for time delays of 300 and 400 ns after optical breakdown reveal the minute extent of self-absorption in air breakdown experiments from (i) differences of electron density determined from the N⁺ lines and the H_α line, and/or from (ii) differences in recorded data sets with/without the mirror for the various time delays in the experiments.

In this work, we investigate effects of doping of hetero-atoms such as Nitrogen (N) on the growth and field emission properties of Carbon Nanotubes (CNTs) in low temperature plasma. A theoretical model is developed to incorporate kinetics of electron, ions and neutral atoms with N as dop ing elements in complex and low temperature plasma. Results of numerical calculations of the radius of N-doped CNT are presented for typical glow discharge plasma parameters. It is found that the radius of CNT is reduced with N-doping. The field enhancement factor of CNT is also estimated from the obtained results.

We consider conditions of strong Langmuir turbulence, for which a wave packet cycle is observed. The dynamics of such intense Langmuir electric fields may affect the line broadening of simple atoms. We use a simple stochastic model to evaluate the effect of such turbulent fields on the Lyman α line in low density plasmas.

We seek to characterize the temperature decay of laser-induced plasma near the surface of an aluminium target from laser-induced breakdown spectroscopy measurements of aluminium alloy sample. Laser-induced plasma are initiated by tightly focussing 1064 nm, nanosecond pulsed Nd:YAG laser radiation. Temperatures are inferred from aluminium monoxide spectra viewed at systematically varied time delays by comparing experimental spectra to theoretical calculations with a Nelder Mead algorithm. The temperatures are found to decay from 5173 ± 270 to 3862 ± 46 Kelvin from 10 to 100 μs time delays following optical breakdown. The temperature profile along the plasma height is also inferred from spatially resolved spectral measurements and the electron number density is inferred from Stark broadened H_β spectra.

The combined relativistic energy approach and relativistic many-body perturbation theory with the zeroth order optimized one-particle approximation are used for calculation of the Li-like ions (Z=11-42,69,70) energies and oscillator strengths of radiative transitions from the ground state to the low-excited and Rydberg states, in particular, 2s_1/2 – np_1/2,3/2, np_1/2,3/2- nd_3/2,5/2 (n=2-12). A comparison of the calculated oscillator strengths with available theoretical and experimental data is performed.

The combined relativistic energy approach and many-body perturbation theory with zeroth model potential approximation are used for computing Blackbody radiation ionization characteristics of the Rydberg atoms, in particular, the sodium in states with n=17,18,40-70. The calculated ionization rate values are compared with available theoretical and experimental data.

Time-resolved spectroscopy is employed to analyze micro plasma generated in laboratory air. Stark-broadened emission profiles for hydrogen alpha and beta allow us to determine plasma characteristics for specific time delays after plasma generation. Stark shift, asymmetry, and full width half maximum measurements are used to infer electron density. The measurements of hydrogen alpha and beta Balmer series line shapes are analyzed using various theory results. Our laser-induced breakdown spectroscopy arrangement uses a Q- switched Nd:YAG laser operating at the fundamental wavelength of 1064 nm that is focused for plasma generation. The hydrogen alpha and beta lines emerge from the free electron background radiation for time delays larger than 0.3 ps and 1.4 ps, respectively. Neutral and ionized nitrogen emission lines allow us to infer electron density for time delays from 0.1 to 10 μs. The electron density values are compared with results obtained from hydrogen Balmer series line shapes.

The effect of plasma compositions (i.e., different concentration of participating ions) on growth, structure and field emission properties of spherical Carbon Nanotube (CNT) tip has been theoretically investigated. In plasma, two different kinds of positively charged ions with heavy to light ion mass ratio of 11.5 are considered and the effect of the different fractional concentrations of participating ions on the growth and field emission properties of CNT is studied. Numerical calculations of the radius of spherical CNT tip for different fractional light ion concentrations have been carried out for the typical glow discharge plasma parameters. It is found that on increasing fractional light ion concentration, the radius of spherical CNT tip decreases and consequently the field emission factor for spherical CNT tip increases.

High-fidelity plasma simulations can be accomplished using microscopic models. However, this is often infeasible for dense plasma problems, in which case continuum models are more economical. Our work has investigated construction of high-fidelity fluid plasma models that retain effects such as displacement current, charge separation effects and plasma wave behaviour.

Carbon Swan spectra are observed following laser ablation of graphene in laboratory air. Previous experiments showed temperatures that ranged from 4500 to 7500 K for the Δv = 0 transition and 4200 to 4500 K for the Δv = −1 transition for time delays on the order of 1.6 μs to 70 μs. This experiment explored in greater detail time delays > 10 μs for both molecular bands. Temperatures were found to be similar, ranging from 4500 to 6700 K for the Δv = 1 transition and 3200 to 5500 K for the Δv = -1 transition. Investigation is also made into spatially resolving the plasma emissions along the slit height. In addition, efforts are made to investigate the applicability of the local thermodynamic equilibrium (LTE) assumption. Comparisons are discussed in view of previous work that utilized Stark broadening of the H_β line, confirming LTE for delays < 10 μs, yet further research needed for later delays.

The atomic and ionic emission lines of titanium are often studied in laser-induced breakdown spectroscopy (LIBS) investigations, partly due to the abundance and luminosity of the lines and titanium's prominence in industry. In the current study, a 13 ns pulsed Nd:YAG laser with 160 mJ per pulse ablates a titanium sample in laboratory air at 10 Hz. Ti III emission lines between 232 nm and 244 nm are observed at 200 ns after laser-surface interaction, utilizing a 6 ns window. Two-dimensional images are obtained, providing spectra emanating along the height of the ablation plume. A Boltzmann plot method is implemented in order to infer electron temperature as a function of height along the plume. The hottest region of the plasma tends to be further away from the sample surface and is on the order of 16000 K.

Broadening and shift of spectral lines in dense Ba and Sr vapor have been studied below and above their first ionization limits. The latter are well-known autoionizing spectral lines that exhibit many different spectral features. However, at larger pressures of noble gases some previously unobserved or very weak spectral phenomena become visible and their studies might be also linked to energy conversion purposes. Originally, we used nanosecond laser which was scanned in a certain spectral region where the two-photon excitation of autoionization lines occurred. This pulsed laser was overlapped by a mode-locked femtosecond laser and a very sensitive thermionic detection was used to observe autoionizing spectral lines. We also presented our preliminary results with hot strontium vapor excited to the resonance level at 460.7 nm.

Solid rocket propellant plume temperatures have been measured using spectroscopic methods as part of an ongoing effort to specify the thermal-chemical-physical environment in and around a burning fragment of an exploded solid rocket at atmospheric pressures. Such specification is needed for launch safety studies where hazardous payloads become involved with large fragments of burning propellant. The propellant burns in an off-design condition producing a hot gas flame loaded with burning metal droplets. Each component of the flame (soot, droplets and gas) has a characteristic temperature, and it is only through the use of spectroscopy that their temperature can be independently identified.

In the present work, the potential of Laser Induced Breakdown Spectroscopy employing femtosecond laser pulses (fs-LIBS) for fuel-air equivalence ratio measurements in premixed methane-air and propane-air flames is presented. A Ti-Sapphire laser system (100 fs, 10 Hz, 800 nm) was used as an excitation source for the plasma creation, while a spectrometer was employed to record the plasma emission spectra. The concentration of the investigated methane-air and propane-air mixtures were expressed by the fuel mole fraction X_fuel and varied from only air - X_fuel=0 (ϕ=0) to only fuel - X_fuel=1 (ϕ=∞). The spectral characteristics of the fs-LIBS spectra are discussed, while the time and energy dependence of the main spectral features are presented. Moreover, from the analysis of fs-LIBS spectra collected at different fuel mole fractions X_fuel, it was found that the fuel variations could be very well correlated with the variation of the intensity of some spectral lines and/or their ratios. The prepared calibration curves of the fuel mole fraction X_fuel versus the atomic line total intensity ratios (H_α 656.3 nm and O (I) 777 nm) and molecular lines total intensity ratios (C₂ 516.5 nm and CN 388.3 nm) suggest the high potential of using fs-LIBS for the determination of the local fuel concentration and its temporal variations.

Strontium is the most popular species for optical lattice clocks. Recent reports of the accuracies from Boulder, U.S. and Tokyo reach 10⁻¹⁸ level, which is better than state-of-the-art caesium clocks more than one order of magnitude. While this achievement accelerates the discussion to redefine the second, the agreement of frequencies in separate laboratories is of critical importance. For this context, intercontinental comparison of Sr lattice clocks were demonstrated between Japan and Germany using a satellite-based technique. The frequency difference was consistent with zero with an uncertainty of 1.6 × 10⁻¹⁵.

This work describes the effect of Gaussian line shape on the comparison of the amplification characteristics (gain) and the Noise figure (NF) of the Thulium and Erbium in the host materials which the Yttria Alumina-Silica glass. The gain using this host material covers the range 1.45-1.65 μm. Thulium-doped fiber amplifiers operated in the region of wavelength (14801510 nm) which is called S-band. The main pump source is 1.04 and 1.55 pm which creates population inversion between 3F4 (upper laser level) and 3H4 (lower laser level), and Erbium- doped fiber amplifiers operated in the region (1510-1650 nm) which is called L -band with the pump wavelength 980 nm. It is found that the erbium doped yttria-alumina silicate fiber amplifier exhibits a maximum gain of 40.3 dB at the central wavelength 1540 nm and minimum noise figure 14 dB, but the broadening in the gain curve is 20 nm. Also it is found that the thulium doped yttria-alumina silicate fiber amplifier exhibits a maximum gain of 27.5 dB at the central wavelength 1467 nm and minimum noise figure 2.5 dB, with the broadening in the gain curve is 41 nm. Gain flatness was investigated and the results strongly confirm the feasibility of using this hosts' glass doped with Thulium in practical ultra large capacity wavelength division multiplexing networks.

Crude petroleum oils are complex mixtures of diverse hydrocarbons, in widely varying compositions, that originate from a variety of geological sources. Fluorescence emission spectra have been measured for two types of Egyptian crude petroleum oil, its light and heavy products over a broad range of excitation and emission wavelengths. Both types of crude oil products are characterized by spectral signatures with a differing topography: the number of fluorescent peaks, their coordinates (λ_ex, λ_em) on the plane of the three dimensions spectrum, and the shape of the bands formed by the contour line density, changeable in either direction. The refined light oil shows emission spectra at λ_max between 350 and 500 nm according to the excitation wavelength. The refined heavy oil shows very broad unstructured emission spectra with λ_max > 400 nm. As a group, they could certainly be distinguished from the light oil samples and most of the crude oil.

In this paper, the challenges of using Particle Image Velocimetry as a diagnostic tool for confined swirling flows are discussed. To highlight these challenges, results from a PIV experiment are compared to a pair of analytical models. While there is generally good qualitative agreement, the velocity measurements degrade in the core of the vortex. Techniques to mitigate the reduced fidelity in this region will be explored and alternative visualization methods will be presented.

As a core component of the proton exchange water electrolyzer system, membrane electrode assemblies degrade due to the corrosion of the material. This creates a loss of interfacial contact necessary for the electron transports and electrochemical reactions, thus decreasing the performance. X-ray diffraction has been demonstrated to be an effective method that readily provides quantitative information about the phase-composition of solid materials. In this study, a group of materials have been selected and tested in the standard conditions for investigating the corrosion mechanisms with X-ray diffraction. The material lattice parameter and the crystal size were examined by X-ray diffraction spectrum.

Proton exchange membrane water electrolyzers (PEMWEs) are a promising energy storage technology due to their high efficiency, compact design, and ability to be used in a renewable energy system. Before they are able to make a large commercial impact, there are several hurdles facing the technology today. Two powerful techniques for both in-situ and ex- situ characterizations to improve upon their performance and better understand their corrosion are electrochemical impedance spectroscopy and energy dispersive x-ray spectroscopy, respectively. In this paper, the authors use both methods in order to characterize the anode gas diffusion layer (GDL) in a PEMWE cell and better understand the corrosion that occurs in the oxygen electrode during electrolysis.

Ultra-narrow cells with the thicknesses in the range from several wavelengths to the small fractions of the wavelength brought a number of new opportunities for atomic spectroscopy. Depending on the cell thickness, spectral lines recorded in ultra-narrow cells are either Doppler-free or Doppler-broadened. With careful selection of the cell thickness hyperfine structure may be easily resolved without resorting on the multibeam nonlinear optical techniques. Moreover, frequent collisions with the walls leads to the important modifications of velocity selective optical pumping resonances. Finally, ultra-narrow cells provide with the unique opportunity to study collisions of the excited atoms with the solid surfaces. In this contribution several examples of the use of the ultra-narrow spectroscopic cells filled with the alkali atomic vapour is presented. First, we discuss general aspects of the transient polarisation that defines all peculiarities of an ultra-narrow cell as a spectroscopic tool. Second, we demonstrate the resolution of the magnetic sublevels in the transition from Zeeman to Paschen-Back regime in the Cs hyperfine structure. Third, new aspects of velocity selective optical pumping resonances in reflection and transmission of resonant radiation by the 6 wavelengths thick cell filled with Cs are discussed. Forth, the experimental evidences of the nonadiabatic transitions between excited states of Rb atoms in the course of collisions with the sapphire surface are presented.

Fluid-wall interactions within solid rocket motors can result in parietal vortex shedding giving rise to hydrodynamic instabilities, or unsteady waves, that translate into pressure oscillations. The oscillations can result in vibrations observed by the rocket, rocket subsystems, or payload, which can lead to changes in flight characteristics, design failure, or other undesirable effects. For many years particles have been embedded in solid rocket propellants with the understanding that their presence increases specific impulse and suppresses fluctuations in the flowfield. This study utilizes a two dimensional framework to understand and quantify the aforementioned two-phase flowfield inside a motor case with a cylindrical grain perforation. This is accomplished through the use of linearized Navier-Stokes equations with the Stokes drag equation and application of the biglobal ansatz. Obtaining the biglobal equations for analysis requires quantification of the mean flowfield within the solid rocket motor. To that end, the extended Taylor-Culick form will be utilized to represent the gaseous phase of the mean flowfield while the self-similar form will be employed for the particle phase. Advancing the mean flowfield by quantifying the particle mass concentration with a semi-analytical solution the finalized mean flowfield is combined with the biglobal equations resulting in a system of eight partial differential equations. This system is solved using an eigensolver within the framework yielding the entire spectrum of eigenvalues, frequency and growth rate components, at once. This work will detail the parametric analysis performed to demonstrate the stabilizing and destabilizing effects of particles within solid rocket combustion.

Materials in nature demonstrate certain spectral shapes in terms of their material properties. Since successful experimental demonstrations in 2000, metamaterials have provided a means to engineer materials with desired spectral shapes for their material properties. Computational tools are employed in two different aspects for metamaterial modeling: 1. Mircoscale unit cell analysis to derive and possibly optimize material's spectral response; 2. macroscale to analyze their interaction with conventional material. We compare two different approaches of Time-Domain (TD) and Frequency Domain (FD) methods for metamaterial applications. Finally, we discuss advantages of the TD method of Spacetime Discontinuous Galerkin finite element method (FEM) for spectral analysis of metamaterials.

In this study, an exact solution is provided for a previously indeterminate equation used for rotor blade fault diagnostics. The method estimates rotor blade natural frequency through turbine engine casing pressure and vibration sensors. The equation requires accurate measurements of low-amplitude sideband signals in the frequency domain. With this in mind, statistical evaluation was also completed with the goal of determining the effect of sampling time and frequency on sideband resolution in the frequency domain.

This study relies on computational fluid dynamics (CFD) tools to analyse a possible method for creating a stable quadrupole vortex within a simulated, circular-port, cylindrical rocket chamber. A model of the vortex generator is created in a SolidWorks CAD program and then the grid is generated using the Pointwise mesh generation software. The non-reactive flowfield is simulated using an open source computational program, Stanford University Unstructured (SU2). Subsequent analysis and visualization are performed using ParaView. The vortex generation approach that we employ consists of four tangentially injected monopole vortex generators that are arranged symmetrically with respect to the center of the chamber in such a way to produce a quadrupole vortex with a common downwash. The present investigation focuses on characterizing the flow dynamics so that future investigations can be undertaken with increasing levels of complexity. Our CFD simulations help to elucidate the onset of vortex filaments within the monopole tubes, and the evolution of quadrupole vortices downstream of the injection faceplate. Our results indicate that the quadrupole vortices produced using the present injection pattern can become quickly unstable to the extent of dissipating soon after being introduced into simulated rocket chamber. We conclude that a change in the geometrical configuration will be necessary to produce more stable quadrupoles.

In this work we describe a summary of flow control research studies on active, passive and adaptive methodologies designed to attenuate large scale flow unsteadiness and the resulting pressure fluctuations in cavity flows. Spectral analysis of high frequency dynamic pressure measurements is used to determine the control effectiveness. Various control techniques, depending on their geometry and or distribution, can be advantageous in attenuating both the peaks and the broad spectral bands generated by flow unsteadiness. Increased effectiveness is associated with redistribution of the shear-layer vorticity. Combination of experimental and numerical results assists in understanding the underlying flow physics and interaction processes involved.