Spatiotemporal evolution of emission and absorption signatures in a laser-produced plasma

We report spatiotemporal evolution of emission and absorption signatures of Al species in a nanosecond (ns) laser-produced plasma (LPP). The plasmas were generated from an Inconel target, which contained similar to 0.4 wt. % Al, using 1064 nm, approximate to 6 ns full width half maximum pulses from an Nd:YAG laser at an Ar cover gas pressure of approximate to 34 Torr. The temporal distributions of the Al I (394.4 nm) transition were collected from various spatial points within the plasma employing time-of-flight (TOF) emission and laser absorption spectroscopy, and they provide kinetics of the excited state and ground state population of the selected transition. The emission and absorption signatures showed multiple peaks in their temporal profiles, although they appeared at different spatial locations and times after the plasma onset. The absorption temporal profiles showed an early time signature representing shock wave propagation into the ambient gas. We also used emission and absorption spectral features for measuring various physical properties of the plasma. The absorption spectral profiles are utilized for measuring linewidths, column density, and kinetic temperature, while emission spectra were used to measure excitation temperature. A comparison between excitation and kinetic temperature was made at various spatial points in the plasma. Our results highlight that the TOF measurements provide a resourceful tool for showing the spatiotemporal LPP dynamics with higher spatial and temporal resolution than is possible with spectral measurements but are difficult to interpret without additional information on excitation temperatures and linewidths. The combination of absorption and emission TOF and spectral measurements thus provides a more complete picture of LPP spatiotemporal dynamics than is possible using any one technique alone.

Automated summary

We present the spatiotemporal evolution of emission and absorption signatures of Al species in a nanosecond laser-produced plasma (LPP). The measurements were conducted using time-of-flight (TOF) emission and laser absorption spectroscopy, providing kinetic information of the excited state and ground state populations. Multiple peaks were observed in the temporal profiles of the emission and absorption signatures, corresponding to different spatial locations and times. The absorption spectra were used to measure linewidths, column density, and kinetic temperature, while the emission spectra were used to measure excitation temperature. The combination of TOF and spectral measurements offers a more complete understanding of the spatiotemporal dynamics of the LPP.