Spatial analysis of band emission from laser produced plasma

Time and space resolved spectroscopic studies of the molecular band emission from are performed in the plasma produced by irradiating a graphite target with m radiation from a Q-switched Nd:YAG laser. High-resolution spectra are recorded from points located at distances up to 15 mm from the target in the presence of ambient helium gas pressure. Depending on the laser irradiance, time of observation and position of the sampled volume of the plasma the features of the emission spectrum are found to change drastically. The vibrational temperature and population distribution in the different vibrational levels of molecules have been evaluated as a function of distance for different time delays and laser irradiance. It is also found that the vibrational temperature of molecules decreases with increasing helium pressure.