Pressure scaling of the collisional broadening parameters of Kr 4p⁶S01→→5p[3/2]₂ transition

Pressure scaling of collisional broadening parameters of krypton (absorber) 4p⁶S01→→5p[3/2]₂ transition centered at 107.3 nm in the presence of nitrogen N₂ (perturber) is investigated. The absorption spectrum in the vicinity of the transition is obtained from the two-photon excitation scan of krypton in the presence of the perturber at different prescribed pressures varying from a few torrs to 10 atm. The absorption spectra reveal noticeable asymmetry at atmospheric pressure, and the asymmetry becomes increasingly pronounced with pressure; however, the absorption spectra at sub-atmospheric pressures tested are symmetric. The absorption spectra are fitted with synthetic asymmetric Voigt profiles across all pressures, wherein the asymmetry parameter is varied to capture the asymmetry at different pressures. The collisional shift (δ_C), the symmetric equivalent collisional full width at half maximum (w), and the asymmetry parameter (a) are determined from the synthetic fits at various pressures. All the parameters are observed to vary linearly with pressure over the entire range of the pressure values tested. The mechanisms that cause the asymmetry in the absorption spectra are also discussed.