Abstract: | The emission spectrum of the PSe radical is reported for the first time. Seventy-eight reddegraded bands in the region 4000–6500 Å have been measured and assigned to the A2Π-X2Π transition of PSe. Isotope shifts observed for some bandheads have been utilized in deriving the vibrational numbering. The molecular constants have been determined as (in units of cm−1): ω′ = 406.9, ω′eχ′e = 1.3, ω″ = 556.9, ω″eχ″e = 1.3, and Te = 19477.3 for the 2Π1/2 states; and ω′e = 402.4, ω′eχ′e = 1.5, ω″e = 556.8, ω″eχ″e = 1.6, and Te = 19178.0 for the 2Π3/2 states. |