A theoretical and experimental study of the HPCl radical: the Ã2A′→X̃2A″ visible emission spectrum

We report the first observation of the Ã2A′→X̃2A″ visible emission spectrum of HPCl. The spectrum shows a series of blue-degraded bands with two prominent progressions in the ground state bending vibration. Ab initio calculations are used to help to assign the observed spectrum. The experimentally derived constants are T0=21 305 cm−1, ω″2=868 cm−1, ω2′=622 cm−1 and ω3′=529 cm−1 compared with calculated values of T0=23 518 cm−1, ω″2=893 cm−1, ω2′=670 cm−1 and ω3′=524 cm−1. The bending progression results from a substantial change in the bond angle between the ground and electronically excited states from 96° to 118°.