High resolution spectral analysis of lithium plasma formed by single and double laser ablation has been undertaken to understand the plume-laser interaction, especially at the early stages of the plasma plume. In orde...High resolution spectral analysis of lithium plasma formed by single and double laser ablation has been undertaken to understand the plume-laser interaction, especially at the early stages of the plasma plume. In order to identify different atomic processes in evolving plasma, time resolved spectral emission studies at different inter-pulse delays have been performed for ionic and neutral lithium lines emitting from different levels. Along with the enhancement in emission intensity, a large line broadening and spectral shift, especially in the case of excited state transition Li I 610.3 nm have been observed in the presence of the second pulse. This broadening and shift gradually decrease with increasing time delay. Another interesting feature is the appearance of a multi-component structure in the ionic line at 548.4 nm and these components change conversely into a single structure at the later stages of the plasma. The multi-component structures are correlated with the presence of different velocity （temperature） distributions in non-LTE conditions. Atomic analyses by computing photon emissivity coefficients with an ADAS code have been used to identify the above processes.展开更多
文摘High resolution spectral analysis of lithium plasma formed by single and double laser ablation has been undertaken to understand the plume-laser interaction, especially at the early stages of the plasma plume. In order to identify different atomic processes in evolving plasma, time resolved spectral emission studies at different inter-pulse delays have been performed for ionic and neutral lithium lines emitting from different levels. Along with the enhancement in emission intensity, a large line broadening and spectral shift, especially in the case of excited state transition Li I 610.3 nm have been observed in the presence of the second pulse. This broadening and shift gradually decrease with increasing time delay. Another interesting feature is the appearance of a multi-component structure in the ionic line at 548.4 nm and these components change conversely into a single structure at the later stages of the plasma. The multi-component structures are correlated with the presence of different velocity （temperature） distributions in non-LTE conditions. Atomic analyses by computing photon emissivity coefficients with an ADAS code have been used to identify the above processes.
