The virtual atomic and molecular data centre (VAMDC) consortium^*

The VAMDC e-infrastructure has evolved over the years through successive releases (Rixon et al 2011, Doronin et al 2012, Dubernet et al 2015). The current version of standards and software is release version v12.07. The VAMDC Standards include the definition of data models for atomic and molecular data, the definition of 'keywords', the definition of query protocols and data access, the definition of registries, of units, of versioning processes, and the establishment of a uniform protocol for web application to process XML schema for atoms, molecules and solids (XSAMSs) files. All Standards Documents can be found on http://standards.vamdc.eu/. Below we provide here a brief explanation of some of the key features of these standards.

2.1.1. Data model and XSAMS files

The exchange of heterogeneous atomic and molecular data requires that the relevant parts of physics and chemistry be translated into a computing framework. XSAMS is an XML implementation of the VAMDC data model which is used to build the computer framework. The processes being represented by XSAMS are essentially quantum-mechanical in nature.

XSAMS provides a standard approach to the description of atomic and molecular (A + M) physics in terms of physical processes connecting different quantum-states of atoms and molecules. The identification of the states is standardised by XSAMS to promote matching of corresponding states between databases. Several levels of detail are supported by XSAMS for the description of states and a range of coupling schemes may be specified. States of molecules are identified by tuples of the most-relevant quantum numbers, different tuples being specified in XSAMS for different classes of molecules. XSAMS describes both radiative and collisional transitions between states. The description of collisions may include chemical changes and interactions with elementary particles. The environment in which the transitions occur may be specified, with the main emphasis being on events in the gas phase, but improved support is planned for solid and liquid environments. Cross-sections, both differential and total, for the reactions may be included, and these may be expressed in either tabular or parametric form.

Finally, since the origin and history of the data are necessary for data assessment, XSAMS imposes strict requirements on the traceability of the data, with mandatory inclusion of information on data sources and the methods used to generate specific sets of data. Similarly XSAMS also enforces the rigorous use of standardised units systems and facilitates the provision of uncertainties with the data provided. XSAMS was initially developed (Ralchenko et al 2009) through the joint efforts of researchers from the International Atomic Energy Agency (IAEA), National Institute of Standards and Technology (USA), Oak Ridge National Laboratory (USA), Université Pierre et Marie Curie and Observatoire Paris-Meudon (France), with contributions from the All-Russian Institute of Technical Physics (Russia). The VAMDC Consortium has further developed XSAMS, which then became VAMDC-XSAMS and implemented its logic in all the software used within the VAMDC e-infrastructure. An agreement between the VAMDC Consortium and the IAEA makes the IAEA curator of the stable developed versions of VAMDC-XSAMS (Braams et al 2016), currently VAMDC-XSAMS version 1.0 released in July 2012 (http://standards.vamdc.org/#data-model).

Figure 2 provides an example of the use of XSAMS (Endres et al 2014) provided by the CDMS database (Mueller et al 2005).

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2.1.2. Registry of services

Many queries select by atomic and molecular species, and the names for species vary between scientific communities. VAMDC maintains a database of names, called the 'species database' from which community-specific terms may be refined into standard identifiers understood by all VAMDC nodes. VAMDC identifiers are based on InChIkeys (Heller et al 2015). In most cases, the VAMDC identifier is just the standard InChIkey, but in special cases a suffix is added to distinguish molecular conformers. One copy of the species database is encapsulated in the web portal. Another copy is available for query by applications as a VAMDC data-node. We have designed software which updates the species database when a new species is introduced in any of the VAMDC-connected databases. Copies of the Species Database are distributed to user client software to allow the same query capability as the portal. Table 2 gives two sample entries from the species database. This species database is a key component of the interoperability within the VAMDC e-infrastructure.

VALD (Piskunov et al 1995) is a collection of critically evaluated laboratory parameters for individual atomic transitions, complemented by theoretical calculations. VALD is actively used by astronomers for stellar spectroscopic studies—model atmosphere calculations, atmospheric parameter determinations, abundance analysis etc. The two first VALD releases (Piskunov et al 1995, Kupka et al 1999) contained parameters for atomic transitions only. In a major upgrade, VALD3, publically available from the spring of 2014, the atomic data was extended to cover elements from hydrogen to uranium, and also complemented with parameters for molecular transitions (Ryabchikova et al 2015). An evaluation procedure which involves a comparison with a selection of high-precision stellar spectra is described by (Ryabchikova et al 1999) and (Ryabchikova et al 2008). At present the Moscow VALD-VAMDC node serves high-quality atomic data only (about 2 million transitions). The Uppsala node contains all collected transitions (about 177 million) and is, therefore, suitable for applications such as opacity calculations. The Moscow node is limited to transitions between the experimentally measured energy levels (hence precise wavelengths) and is more tuned for high-resolution spectroscopic analysis. From 2016 Moscow and Uppsala nodes will also run the mirrors of each other for enhanced reliability.

CHIANTI (www.chiantidatabase.org), first released in 1996 (Dere et al 1997), is a well-established atomic database for ions of astrophysical importance. Combined with spectroscopic diagnostic programs, it is used in the analysis of optically thin collisionally ionised plasmas. The CHIANTI database contains atomic structure data (experimental and calculated wavelengths and radiative data), and rates for electron and proton collisions, as well as for ionisation and recombination. The data are mostly obtained from published literature, and are regularly assessed and updated. The latest version 8 of CHIANTI (Del Zanna et al 2015), contains a large number of new atomic data for several isoelectronic sequences, calculated within the UK atomic processes in astrophysical plasmas (APAP) network (www.apap-network.org). APAP/CHIANTI data are used world-wide by almost all atomic databases and modelling codes for astrophysical plasmas. For example, by the modelling codes for photoionised plasmas such as Cloudy (Ferland et al 2013) and MOCASSIN (Ercolano et al 2008); by modelling codes for the x-rays such as PINTofALE (Kashyap and Drake 2000) and ISIS (Houck and Denicola 2000); hydrodynamic codes such as HYDRAD (Bradshaw and Mason 2003) and RADYN (Allred et al 2015); spectral modelling of supernovae such as TARDIS (Kerzendorf and Sim 2014); and atomic databases such as XSTAR (Bautista and Kallman 2001), Stout (Lykins et al 2015), ATOMDB (Smith et al 2001). The CHIANTI basic data is available via VAMDC, and version 8 is being added.

The NIST ASD at http://www.nist.gov/pml/data/asd.cfm contains critically evaluated standard reference data on energy levels, spectral lines, and radiative transitions in atoms and ions of 110 elements from H to Ds. As of November 2015, ASD offers detailed information on more than 109 000 levels and 250 000 spectral lines, in particular, level identifications (configurations, terms, total angular momentum, etc) and radiative decay rates for almost 100 000 transitions. All data in ASD are carefully analysed and evaluated and proper uncertainties for numerical values are derived. ASD also offers several graphical data manipulation tools, e.g., dynamic Grotrian diagrams and Saha-local thermodynamic equilibrium spectra, as well as spectroscopic diagnostic information for ions of several astrophysically abundant elements.

The Spectr-W³ project is the collaboration between the Russian Federal Nuclear Centre All-Russian Institute of Technical Physics (RFNC VNIITF) and the Joint Institute for High Temperatures of the Russian Academy of Sciences (JIHT RAS). The information accumulated in the Spectr-W³ (Faenov et al 2002) atomic database contains over 450 000 records and includes experimental and theoretical data on ionisation potentials, energy levels, wavelengths, radiation transition probabilities, oscillator strengths, and (optionally) parameters providing analytical approximations for electron-collisional cross-sections and rates for atoms and ions. These data were extracted from the scientific literature or provided directly by authors. The information is supplied with references to the original sources and comments, elucidating the details of experimental measurements or calculations, where necessary and available. At the present time, Spectr-W³ is the largest available database providing information on the spectral properties of multicharged ions. A new development of the Spectr-W³ atomic database started in 2014 will create a new section containing information on x-ray emission spectrograms recorded at various plasma sources. Software for this section is currently being created and tested. The spectrograms, mostly obtained in the laser-produced-plasma experiments are also in preparation. Spectr-W³ is hosted at http://spectr-w3.snz.ru/.

Atomic data calculated within the framework of the international opacity project (OP) and iron project (IP) are available in TOPbase (the OP database for radiative processes) (Seaton 1987, Cunto and Mendoza 1992, Cunto et al 1993) and TIPbase (the IP database, for collisional and radiative processes) (Hummer et al 1993). Included are energy levels/terms, radiative transitions probabilities, photoionisation cross sections and collision strengths for a large selection of ions in the range H to Ni. These theoretical data have been calculated using state-of-the-art computer programs such as various versions of the R-matrix suite of codes (Berrington et al 1995, Berrington and Ballance 2002), superstructure (Eissner et al 1974) and autostructure (Badnell 2011) or CIV3 (Hibbert 1975, Hibbert et al 1991). Within their range of validity, the OP and IP data remain a widely used reference set for both producers and users of atomic data. They are relevant for experiment analysis, theoretical comparisons and for various atrophysical or laboratory experiment applications. The OP radiative data are used to calculate monochromatic and mean opacities (Badnell et al 2005) required notably in stellar codes or for the analysis of experiments. TOPbase and TIPbase are hosted at http://cdsweb.u-strasbg.fr/OP.htx.

The Stark-B (Sahal-Bréchot et al 2015) database is a collaborative project between the Laboratoire d'Etude du Rayonnement et de la matire en Astrophysique and the Astronomical Observatory of Belgrade. The database contains calculated widths and shifts of isolated lines of atoms and ions due to electron and ion collisions (Stark broadening parameters), calculated in a series of papers by Dimitrijevi'c, Sahal-Br'echot and their co-workers, using the semiclassical-perturbation approach developed by Sahal-Bréchot (1969a, 1969b, 1974) supplemented by Fleurier et al (1977), and updated by Dimitrijević and Sahal-Bréchot (1984) and in subsequent papers (see Dimitrijević and Sahal-Bréchot 2014).

The database's principal purpose is to provide the Stark broadening data needed for the modelling and spectroscopic diagnostics of stellar atmospheres and envelopes but it is also useful for laboratory plasmas, as well as for laser produced, fusion and technological plasmas. Various astrophysical and other applications of data in STARK-B are discussed by Dimitrijević and Sahal-Bréchot (2014). Data are provided for a wide range of temperatures and electron or ion densities. Hence the range of temperatures and densities covered by the tables is wide and depends on the ionisation degree of the considered ion. Stark-B is hosted at http://stark-b.obspm.fr/.

The CDMS (Mueller et al 2005) provides transition frequencies of atoms and molecules mostly for radio astronomical observations. The included species have been or may be observed in the interstellar medium (ISM), in the circumstellar envelopes (CSEs) of very young and very old stars, or in planetary atmospheres. As of October 2015, 789 species are available which refer not only to the main isotopic species and the ground vibrational state, but also to minor isotopic species and excited vibrational states as far as these may be of interest for radio astronomers. The catalogue is similar to that of the Jet Propulsion Laboratory (Pickett et al 1998 and while duplication is avoided, nevertheless, some overlap exists. CDMS welcomes outside contributions after critical evaluation. As a partner of the VAMDC, the CDMS is accessible from the general VAMDC portal, from the SPECTCOL tool (Dubernet et al 2012), from CDMS new interface (http://cdms.ph1.uni-koeln.de/cdms/portal/) and from its traditional user interface http://www.astro.uni-koeln.de/cdms. CDMS is hosted at http://www.cdms.de.

The submillimetre, millimetre, and microwave spectral line catalogue (Pickett et al 1998) has provided the astrophysics community with atomic and molecular absorption/emission spectral data for over 35 years. The catalogue listings include line-by-line tabulations for each spectral feature, as well as source documentation. As for CDMS, entries are prepared with the quantum mechanical software SPFIT/SPCAT (Pickett 1991), which provides a well-founded and thoroughly tested common basis for the molecular physical data.

The HITRAN database (Rothman et al 2013) is a long-standing compilation of molecular spectroscopic parameters that are required for radiative-transfer codes. This latest edition of HITRAN has a traditional line-by-line high resolution section that contains essential spectral parameters for 47 molecules along with their significant isotopologues appropriate for the terrestrial atmospheric and diverse room temperature applications. There is a section that contains high-resolution experimental cross-sections for so-called heavy molecules, including, for example, the chlorofluorocarbons and halocarbons, that are not amenable to full quantum-mechanical description as in the traditional part of HITRAN. There is also a section of the compilation that provides collision-induced absorption cross-sections. Recently the traditional line-by-line part of HITRAN has been restructured (Hill et al 2013) in order to expand the capabilities to address the issues of planetary atmospheres as well as more sophisticated line shapes. The HITRAN database contains explicit and convenient citations to all source data, and in fact in many cases has raised the impact factor of contributors (Gordon et al 2016).

SMPO is an information system (Babikov et al 2014) devoted to the high resolution spectroscopy of the ozone molecule, related properties and data sources. SMPO contains information on original spectroscopic data recovered from comprehensive analyses and modelling of experimental spectra as well as associated software for data representation written in PHP Java Script, C++ and FORTRAN. The line-by-line list of vibration–rotation transitions, energy levels, transition moments and other related information can be requested from SMPO via the VAMDC portal. Considerable new spectroscopic information has been included using extended analysis of ozone in the infrared (Barbe et al 2007, 2013, De Backer-Barilly et al 2006). SMPO also contains supplementary information to that of HITRAN (Rothman et al 2013) and GEISA (Jacquinet-Husson et al 2011): spectroscopic parameters, theoretical predictions for high-energy states of various isotopologues from potential energy surfaces (Holka et al 2010, Tyuterev et al 2013) as well as assigned data near the dissociation threshold (Campargue et al 2008, Barbe et al 2011, Tyuterev et al 2014) that could be useful for scientists exploring the dynamics of ozone. Applications for the SMPO may include: education/training in molecular physics, radiative processes, laser physics; spectroscopic applications (analysis, Fourier transform spectroscopy, atmospheric optics, spectroscopic atlases); applications to environmental studies and atmospheric physics (remote sensing) and photochemistry (laser excitation, multiphoton processes). SMPO can be accessed via Reims (http://smpo.univ-reims.fr) and Tomsk (http://smpo.iao.ru) sites providing supplementary functionalities of relational database under control of MySQL database tools including graphical interface for theoretical spectra simulation and comparisons with experimental records.

The MeCaSDa, ECaSDa, TFMeCaSDa and SHeCaSDa databases (Ba et al 2013) provide calculated spectroscopic data for the CH₄, C₂H₄, CF₄ and SF₆ molecules, respectively, including isotopologues. These databases not only provide spectroscopic line lists (line positions, intensities and line broadening coefficients) for infrared absorption and Raman scattering spectra, but also a full description of molecular eigenstates with all quantum numbers. The data result from the most recent fits of experimental data, see for example (Nikitin et al 2013, Amyay et al 2015) for CH₄, (Ballandras et al 2013) for C₂H₄, (Faye et al 2014) for SF₆ and (Boudon et al 2011, 2013) for CF₄. All analysis calculations are performed using the XTDS software package (Wenger et al 2008). These databases are complementary to other databases, such as HITRAN (Rothman et al 2013), which mostly rely on experimental data. The calculated data may be less accurate in some spectral regions, but the calculated data sets are more complete since all information is calculated in a given spectral region. The databases are hosted at http://vamdc.icb.cnrs.fr/PHP/methane.php, http://vamdc.univ-reims.fr/PHP/ethylene.php, http://vamdc.icb.cnrs.fr/PHP/CF4.php and http://vamdc.icb.cnrs.fr/PHP/SF6.php.

The CDSD for atmospheric applications contains spectral line parameters of the seven atmospherically most-abundant isotopologues of the carbon dioxide molecule: ¹⁶O¹²C¹⁶O, ¹⁶O¹³C¹⁶O, ¹⁶O¹²C¹⁸O, ¹⁶O¹²C¹⁷O, ¹⁶O¹³C¹⁸O, ¹⁶O¹³C¹⁷O, ¹⁸O¹²C¹⁸O. The line parameters (line position, line intensity, energy of lower state, air-broadening coefficient, self pressure-induced broadening coefficient and exponent of temperature dependence of air broadening coefficients) have calculated values. The CDSD-296 databank covers the 5.9–12784.1 cm⁻¹ spectral range and contains more than 419 600 lines. This line list was generated using an intensity cutoff of 10⁻³⁰ cm/molecule at a reference temperature of 296 K. Recently the CDSD-296 databank (Tashkun et al 2015) has been extended to include all 12 stable carbon dioxide isotopologues, and the full database will be available through the VAMDC portal in 2016. The CDSD-1000 databank (Tashkun et al 2003) covers the spectral range 257–9648 cm⁻¹ and contains more than 3950 500 lines. The line list has been generated using an intensity cutoff of 10⁻²⁷ cm/molecule at a reference temperature of 1000 K. The databanks are hosted in Tomsk at ftp://ftp.iao.ru/pub/CDSD-296 and ftp://ftp.iao.ru/pub/CDSD-1000.

The ExoMol project (Tennyson and Yurchenko 2012) provides computed line lists for molecules likely to be of importance in hot atmospheres such as those of extrasolar planets and cold stars. Because of the elevated temperatures in these environments, a very large number of transitions must be included in spectral simulations: up to 10¹¹ lines in some cases. To ease the computational burden involved in the calculation of opacities (which in many practical cases are not required at high resolution), ExoMol provides pre-calculated absorption cross sections (Hill et al 2013) at a range of temperatures through a service on the project website (http://www.exomol.com/xsecs/). The ExoMol database has just undergone a comprehensive upgrade to its data structures (Tennyson et al 2016). ExoCross is a VAMDC database node which provides access to these cross sections through the VSS2 query language. Data is returned in the XSAMS format for interoperability with other data returned by VAMDC services. ExoCross is hosted at www.exomol.com where a considerable amount of other spectroscopic data can be found for the molecules concerned.

SESAMs is devoted to the spectroscopic analysis of UV electronic spectra of diatomic molecules. Data for H₂, HD, D₂ and CO are presently available as a whole dataset or can be searched within a defined wavelength window. Other selection criteria are available such as the energy of the lower (upper) level of the transition and the oscillator strength value. The data are obtained from theoretical calculations which include rotational and radial perturbations between electronic potential curves (Abgrall et al 1993, 1994). They have been tested carefully against experimental values when available (Abgrall et al 1994, Liu et al 2007, Gabriel et al 2009). They are useful in various contexts, ranging from plasma laboratories (Gabriel et al 2009) to planetary (Barthélemy et al 2014), interstellar (France et al 2011, 2012, 2014) or extragalactic environments (Salumbides et al 2015). SESAM is hosted at http://sesam.obspm.fr/.

The W@DIS information system (Polovtseva et al 2012, Tennyson et al 2013, 2014) is designed to provide access to data, information, and ontologies relating to quantitative spectroscopy required for solving fundamental and applied problems pertaining to a number of subject domains: atmospheric optics, astronomy, etc. The information system under discussion is a prototype of the next generation information system on molecular spectroscopy based on Semantic Web technologies (Berners-Lee et al 2001, Fazliev et al 2013). The system focuses on spectral data representation for the end user with the possibility of employing information characterised by different levels of details both for the structure of the data and for the knowledge (semantic annotations) associated with these data. It is the end user who makes the decision about the level of detail required. W@DIS divides molecular spectroscopic data into three parts: parameters for energy levels, transitions, and line profiles. Most of the molecular data are accessible via VAMDC portal. W@DIS is hosted at http://wadis.saga.iao.ru.

The Cagliari-Toulouse PAH theoretical spectral database (Malloci et al 2007) is a joint effort by the groups of Mulas (INAF-OAC) and Joblin (Univ. Toulouse III/CNRS-IRAP), aimed at providing all the 'ingredients' needed for modelling of the photophysics of individual PAHs in space, mainly in photon-dominated interstellar and circumstellar environments. It includes basic structural properties of PAHs in four charge states (−1, 0, +1, and +2), ionisation potentials and electron affinities, harmonic vibrational analyses, vertical photoabsorption electronic spectra. Recent examples of the use of the data in this database are e.g. Berné et al (2015), Zhen et al (2015), Zonca et al (2015). All these data were obtained in the framework of the density functional theory, (see Jones 2015 for a recent review), and some on-going work (van Mourik 2014), in its time-independent formulation for ground electronic state properties and in its time-dependent formulation for photoabsorption spectra. Data were obtained using the Gaussian (Frisch et al 2004), NWChem (Valiev et al 2010), and Octopus (Andrade et al 2015) computer codes.

The KIDA (Wakelam et al 2012), is a compilation of kinetic data (chemical reactions and associated rate coefficients) used to model the chemistry in astrophysical environments (the interstellar medium, protoplanetary disks, planetary atmospheres etc). In addition, to detailed information of each reaction (temperature range of validity of the rate coefficients, reference, uncertainty etc), particular attention is given to the quality of the data which is evaluated by a group of experts in the field. The 2014 update has just been released (Wakelam et al 2015). KIDA is hosted at http://kida.obs.u-bordeaux1.fr.

The UMIST database for astrochemistry (McElroy et al 2013) contains reaction rate coefficients and related material for the study of chemical kinetic modelling of astronomical sources, including molecular clouds, CSEs and shocked gas. The main part of the database Rate12, which is the fifth public release of the data, is a set of 6173 gas-phase reactions and temperature-dependent rate coefficients among 467 species and involving 13 elements (McElroy et al 2013). In this release particular emphasis has been placed on identifying the source of the data; DOI codes and web links to the original papers are provided where possible. In parallel, a comprehensive, searchable web site has been developed which includes other relevant data including deuterium exchange reactions and state-selective ortho–para reactions among hydrogen and deuterium, both of which are essential for calculations of deuterium fractionation in interstellar clouds, a set of binding energies for atoms and molecules on interstellar ices and a set of three-body reactions and rate coefficients that are important at very high densities. The web site also provides fully commented codes and documentation for calculations of abundances in molecular clouds and CSEs together with related perl scripts and instructions for generating the ODEs and plotting routines. Software that turn the abundance outputs into line intensities and profiles is being developed. UDfA is hosted at www.udfa.net.

The BASECOL2012 database (Dubernet et al 2013) is a repository of collisional data. It contains rate coefficients for the collisional excitation of rotational, ro-vibrational, vibrational, fine, and hyperfine levels of molecules by atoms, molecules, and electrons, as well as fine-structure excitation of some atoms, that are relevant to interstellar and circumstellar astrophysical applications. In addition, BASECOL2012 provides spectroscopic data queried dynamically from various spectroscopic databases using the VAMDC technology. These spectroscopic data are conveniently matched to the in-house collisional excitation rate coefficients using the SPECTCOL software package (Dubernet et al 2012), and the combined sets of data can be downloaded from the BASECOL2012 website. As a partner of the VAMDC, BASECOL2012 is accessible both from the general VAMDC portal and from user tools such as SPECTCOL. Submissions of newly published collisional rate coefficients sets are critically evaluated before inclusion in the database which is hosted at http://basecol.obspm.fr. The BASECOL database contains explicit citations to all source data; the authors' publications can be easily retrieved from the BASECOL website and from both the SPECTCOL tool and the VAMDC portal through the 'bibtex' visualisation software.

MOLD (Vujčić et al 2015) contains photo-dissociation cross-sections for the individual ro-vibrational states of the diatomic molecular ions and rate coefficients for the atom–Rydberg atom chemi-ionisation and inverse electron–ion–atom chemi-recombination processes. At the moment MOLD contains data for photodissociation cross-sections of the hydrogen H₂⁺ (Mihajlov et al 2007) and helium He₂⁺ (Mihajlov et al 2009) molecular ions and the corresponding averaged thermal photodissociation cross-sections. MOLD is hosted at the Belgrade Astronomical Observatory, http://servo.aob.rs.

The database is maintained by the 'Laboratorio di Astrofisica Sperimentale' (Catania-LASp for short), Catania, Italy. LASp spectra are taken by using in situ techniques and equipment especially developed to analyse the effects of irradiation (ion and/or UV photons) and thermal cycling (down to 10 K) by infrared, Raman and UV-VIS-NIR spectroscopy. Analysed materials include frozen gases, solids samples and meteorites. The main application field up until now has been in astrophysics, and over the years many hundreds of ice mixtures of various compositions and of solids have been studied (Baratta et al 1991, Strazzulla et al 1991, Baratta et al 1994, Leto et al 1996, Scollo et al 2013, Sabri et al 2015). Through the VAMDC portal, transmission and optical depth data for water-ice experiments are available for the temperature range from 12.5 to 150 K (Baratta et al 2003, Leto and Baratta 2003). The public database also includes optical constants of solid state CO, CO₂ (Baratta and Palumbo 1998, Palumbo et al 2006), and CH₄ (Brunetto and Roush 2008) deposited at various temperatures. LASP is hosted at http://vamdclasp.oact.inaf.it/GUI/index and additional information can be found at http://web.ct.astro.it/weblab/.

The GhoSST database provides experimental data and products on: (1) transmission spectra of ices, sulfur compounds, minerals, organic and meteoritic material in the wavelength range from the visible to the far-IR; (2) absorption coefficients and optical constants of ices; (3) bidirectional diffuse reflection spectra of granular surfaces (hydrated minerals, adsorption on minerals, ices, natural and synthetic organic materials, meteorites, ...) from Visible to near-IR; (4) bidirectional reflection spectra of granular surfaces simulated with a radiative transfer model (Spectrimag) using laboratory optical constant data; (5) infrared micro-spectroscopy of minerals, natural organics, and meteorites; (6) Raman and fluorescence micro-spectroscopy of cosmomaterials (meteorites, IDPs, Stardust, ...) and planetary analogs; (6) lists of vibration bands of molecular solids and molecules adsorbed on solids, from Visible to far-IR. Only the linelists are currently accessible from the VAMDC The GhoSSt database is hosted at http://ghosst.osug.fr/.

The main purpose of DESIRE (database on sixth row elements) is to provide the scientific community with updated spectroscopic information concerning the sixth row elements (Z = 72–86) of the periodic table in their lowest ionisation stages. In the tables, the spectra are classified by elements, and for a given element, by degree of ionisation. For each spectrum, the tables show the wavelengths (in Å) derived from the experimental levels, the lower and upper levels (in cm⁻¹) of the transitions, the calculated weighted oscillator strengths (log gf) and transition probabilities (gA in s⁻¹), and the cancellation factors. The radiative rates listed in this database have been obtained by the Atomic Physics and Astrophysics group of Mons University, Belgium, by means of a systematic and extensive use of the pseudo-relativistic Hartree–Fock (HFR) method (Cowan 1981) modified for taking core-polarisation effects into account (HFR + CPOL) (Quinet et al 1999, 2002). Most of these theoretical results have been validated by the good agreement obtained when comparing computed radiative lifetimes and accurate experimental values measured by the time-resolved laser-induced fluorescence technique. The DESIRE database is hosted at http://hosting.umons.ac.be/html/agif/databases/desire.html.

DREAM (Database on Rare-Earths At Mons University) contains information concerning the wavelengths, the oscillator strengths and the transition probabilities for spectral lines of neutral and lowly ionised lanthanides (Z = 57–71). The format of the tables as well as the methods used for obtaining the listed values are the same as for DESIRE. DREAM is hosted at http://hosting.umons.ac.be/html/agif/databases/dream.html.

The International Atomic Energy Agency (IAEA) ALADDIN (originally 'a labelled atomic data interface') database contains numerical data on atomic and molecular collision processes that are relevant to fusion energy and other plasma applications as well as data on plasma–material interaction processes. The name goes back to a data exchange format developed in the fusion atomic and molecular data community in the 1980s (Hulse 1990), but the present database at IAEA is based on SQL and XSAMS is used for data exchange. ALADDIN2 is a subset of ALADDIN accessible through the VAMDC interface and containing at this time only the gas-phase collisional differential and integrated cross sections and rate coefficients. Data in ALADDIN and ALADDIN2 have largely been produced in coordinated research projects or other activities sponsored by the IAEA or they have been evaluated under auspices of the IAEA. The ALADDIN database is hosted at http://www-amdis.iaea.org/ALADDIN.

Some databases aimed at the radiation damage community have lately adopted the VAMDC standards and are therefore currently accessible in VAMDC: RADAM-ION, IDEABD and BeamDB. Those databases are part of a collaboration that has a created the RADAM portal at http://radamdb.mbnresearch.com/.

3.26.1. IDEABD

3.26.2. RADAM-ION

3.26.3. BeamDB

LXCAT (Pancheshnyi et al 2012) is an open-access website for collecting, displaying, and downloading electron and ion scattering cross sections, swarm parameters (mobility, diffusion coefficient, etc), reaction rates, energy distribution functions and other data required for modelling low temperature plasmas. The available data bases have been contributed by members of the community and are indicated by the contributor's chosen title. The LXCAT website is hosted at http://www.lxcat.net/. The following contributors to LXCAT have chosen to open their data within the VAMDC e-infrastructure and LXCAT maintains this VAMDC access.

3.27.1. Quantemol data

3.27.2. Zatsarinny and Bartschat data

3.27.3. UNAM database

3.27.4. ETHZ database

The Indian atomic and molecular research community has been actively involved in atomic and molecular research for decades, especially in the areas of collision physics, spectroscopy, astrochemistry and chemical kinetics. There is a wide spectrum of activity in both theory and experiment covering collisions of electrons, ions and photons and atomic and molecular spectroscopy (Nandi et al 2005, Ram et al 2009, Vinodkumar et al 2011, Gupta and Antony 2014, Kaur et al 2015). Thus there is an enormous amount of high quality experimental (Krishnakumar et al 1997, Prabhudesai et al 2008, Rawat et al 2008) and theoretical data (Vinodkumar et al 2012, Barot et al 2013, Goswami et al 2013, Nagma and Antony 2014) on atomic and molecular processes being produced by the Indian research community.

Krishnakumar and his collaborators have initiated a programme aimed at the creation of the IAMDB. The aim was two fold: (1) create 'IAMDB' as a repository for the A + M data in India; (2) link it to the VAMDC portal for wider visibility. IAMDB (www.iamdb.co.in) is currently being developed to incorporate data from all the Indian atomic and molecular research groups. Each node in the database is developed independently and the collision node will be ready soon. Later all the nodes will be assembled together to form the complete IAMDB database which will consist of: (1) a collisional data node; (2) an atomic spectroscopy data node; (3) a molecular spectroscopy data node.

3.28.1. The collisional data node

The portal (http://portal.vamdc.eu) is the main single entry point to all VAMDC connected databases. It provides immediate visibility for the available data in the VAMDC connected databases, and in many cases can be the first step towards discovering data since those databases will respond if they contain the requested data. The portal contains several sections: the 'VAMDC Databases' section provides a general description of the VAMDC connected databases and allows display of the species that are available in each database; the 'Guided Query' section is new and provides a query interface for beginners where users are guided step-by-step; the 'Advanced Query' section allows more flexibility in interrogating the databases; The 'info' section provides a link to tutorials which provide a full understanding of the portal's capabilities. Once a query is performed, the user is invited to choose one of the possible tools to visualise the data. These tools are homogeneous between the databases and the description of the retrieved data, in particular of quantum numbers, is also the same across all databases. Such uniformity means that the portal cannot offer the same services as a traditional graphical user interface of the individual databases. This is the price paid for accessing a wide range of data stored in a heterogeneous fashion. Nevertheless, where possible, specific visualisation software is associate with each database. Currently this visualisation software is accessible from '—Choose display—' of the result page (see figure 3), the tools labelled with stars being those that are recommended. The result page is under continuous development in order to meet evolving user needs.

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It should be emphasised that the portal has been tuned towards astrophysical users for spectroscopic applications. Indeed the two visualisation tools called 'molecular spectroscopy XSAMS to HTML' and 'Atomicxsams2HTML' that display, for molecular and atomic spectroscopic data respectively, an HTML page where columns and lines can be selected, allow to export selected data into a VOTable format which is a virtual observatory (VO) standard (http://www.ivoa.net) used to exchange data among VO Tools. The VOTable can be sent to any VO Tool launched on the user's desktop using the 'send via SAMP' functionality of the processor. SAMP is another VO Standard (http://www.ivoa.net/documents/SAMP/) that allows several applications to exchange data directly, without the need to save and load a file locally. As a typical example, a selected data file can be sent to an application called TOPCAT (http://www.star.bris.ac.uk/~mbt/topcat/) which is dedicated to the visualisation of tabular data. All functionalities of TOPCAT can be used on the selected VAMDC data.

The current VAMDC e-infrastructure includes databases related to atomic and molecular spectroscopy and to heavy particle collisional processes, and is appropriate to the type of currently accessible data. Any producer of data can join the VAMDC infrastructure through one of the following methods: (1) they can include their data in existing atomic and molecular databases that are partners of VAMDC; (2) they can create a new database hosted by a partner of VAMDC; (3) they can create a new node in the VAMDC e-infrastructure. VAMDC aims to provide atomic and molecular data providers and compilers with a large dissemination platform for their data. Currently all products related to VAMDC, portal and tools, explicitly encourage users to cite both the original papers where the data have been published and the relevant databases.

The libraries, software modules and software can be found on the VAMDC website⁴⁶ . The integration of the libraries are documented, supported via tutorials and illustrated by scientific case studies (Dubernet et al 2014). Up till now case studies have concentrated on astrophysical applications since the traditional VAMDC collaborators come from the astrophysics communities.

As an example of this, the SPECTCOL tool (Dubernet et al 2012) matches spectroscopic data from CMDS (Mueller et al 2005) and JPL (Pickett et al 1998) with collisional data from BASECOL (Dubernet et al 2013) for interstellar applications. The client tool interrogates the registry to find spectroscopic and collisional information about a molecule. It retrieves different possible sets of data from different databases. The user can associate sets of their own choice to create a customised combination of spectroscopic and collisional data. This automatically resolves the common difficulty met by researchers wishing to combine collisional data from a database such as BASECOL with spectroscopic data coming from other native databases such as CDMS, JPL or any other spectroscopic databases. Combining data involves matching molecular states that are very often described differently in JPL, CDMS and BASECOL. This problem is now resolved easily using XSAMS. A recent example of application of the SPECTCOL tool has been to the study of protoplanetary disks (Öberg et al 2015).

Another example is access of VAMDC connected databases through the BASS2000 web portal (http://bass2000.obspm.fr) that provides access to a wide range of the solar spectra, from 67 to 5400 nm. This overall spectrum is obtained from (Curdt et al 2001) for the UV part using SOHO/SUMER data; from (Delbouille et al 1972) for the visible part, using Kitt Peak National Observatory observations; from (Delbouille et al 1981) for the infrared part, also based on Kitt Peak observations. The visible part of the spectrum is very much used both for preparing and processing observations. Spectro-polarimeters take full advantage of the detailed knowledge of atomic data concerning the observed lines in order to be able to calculate local magnetic field. Therefore, the solar spectral data has been connected to VAMDC in order to provide directly useful information to the user. This helps in data processing, but also in order to prepare observations, for instance tagging atmospheric molecular lines, such as water, that may serve for wavelength calibration.

Two astrophysical software packages have implemented access to the VAMDC e-infrastructure, to provide the capability of analysing interstellar medium spectra. One package is the standalone software called CASSIS (http://cassis.irap.omp.eu), the other is a toolbox (http://www.astro.uni-koeln.de/projects/schilke/myXCLASSInterface) for the common astronomy software applications package that includes the MyXClass program (Moeller et al 2015).

Finally SPECVIEW (http://www.stsci.edu/institute/software_hardware/specview/) is a tool for 1D spectral visualisation and analysis of astronomical spectrograms from STScI that can overplot spectral line identifications taken from a variety of line lists, including user-supplied lists. SPECVIEW has been modified to include the VAMDC query module, called QueryBuilder⁴⁷ , thus providing the full capability to query the VAMDC databases. As an example SPECVIEW is launched automatically to visualise synthetic spectral librairies for the GAIA mission http://gaia.esa.int/spectralib/) and now the user can make detailed selections of observed species and properties of linelists in order to overplot spectral line identifications.

Users might want to create new libraries and software; VAMDC provides support for those activities. The VAMDC Consortium can provide the following services to users: (1) services and tools can be adapted to meet specific user requirements; (2) VAMDC capabilities and facilities can be imported into tools developed by institutes external to the consortium; (3) innovative tools for easily handling and processing results can be provided.