Collisional relaxation of H2CO (Ã 1A2, v4=1, J K a ,K c=132,12) by He, Ar, Xe, and N2

Abstract

The collision-induced deactivation of H2CO in a specific rotational level in its first electronically excited singlet state, Ã 1A2, v4=1, JKa,Kc=132,12, has been investigated with a series of colliders, M=He, Ar, Xe, and N2. The target level was populated via the transition Ã←X̃, 410, 132,12←133,11 using a pulsed dye laser. The subsequent relaxation was monitored using the technique of transient gain spectroscopy (TGS) via the transition Ã→X̃, 201301414, 132,12→131,13, which coincides with the line of an Ar+ laser at λ=488.0 nm. The experiments yielded the overall collisional depopulation rate constants (velocity averaged cross sections) for He, Ar, Xe, and N2, respectively: (5.25±0.20)×10−10 cm3/molecule s (39 Å2), (5.22±0.18)×10−10 cm3/molecule s (86 Å2), (5.37±0.29)×10−10 cm3/molecule s (106 Å2), (8.25±0.29)×10−10 cm3/molecule s (125 Å2), where the uncertainties correspond to the 2σ standard deviations.