Optical emission spectrometric diagnosis of laser-induced plasma and shock front produced at moderate pressure

We present a non-contact optical investigation of laser-induced plasma at moderate Ar pressure ranging from 1 to 100 Pa. The significant shock front and spatial fractionation among the different charged ions are demonstrated at the pressure of 20 Pa. The collisions between Si IV ions and ambient Ar atoms generate distinct and excited Ar II ions, fresh Si III ions, and electrons at the dense layer. The electron density peaks at the position of the shock front, indicating that the collision that yields electrons is dominant over the recombination process in the region of the shock layer and its immediate vicinity.

Automated summary

We conducted a non-contact optical investigation on laser-induced plasma under moderate Ar pressure (ranging from 1 to 100 Pa). At the pressure of 20 Pa, we observed significant shock front and spatial fractionation among different charged ions. Collisions between Si IV ions and ambient Ar atoms result in the generation of distinct and excited Ar II ions, fresh Si III ions, and electrons at the dense layer. Furthermore, we found that the electron density peaks at the position of the shock front, suggesting that the collision process leading to electron generation dominates over the recombination process in the shock layer and its immediate vicinity.