Rotational analysis of the c3Î u-b3Î g system of P2

The rotationally resolved spectra of the c3Πu-b3Πg system of P2 in the 16620-17860 cm−1 region is reanalyzed here to obtain more assignments of the rotational lines and more accurate molecular constants. Approximately 500 spectral lines were assigned to six subbands: the Ω=0, 1 and 2 components of the (2, 3) band, the Ω=0 and 2 components of the (1, 3) band and the Ω=2 component of the (1, 2) band. Because of perturbations in the c3Πu (υ=2) state, the Λ-doubling in the 3Π2-3Π2 subband of the (2, 3) band was resolved. By the weighted nonlinear least-squares fitting using two types of effective Hamiltonians, more accurate molecular constants for the υ′=1 and 2 levels in the c3Πu state and for the υ″=2 and 3 levels in the b3Πg state of P2 were derived.

► Rotationally resolved spectra in the c3Πu-b3Πg system of P2 were observed. ► Approximate 500 spectral lines were assigned to the (2, 3), (1, 3) and (1, 2) bands. ► The Λ-doubling in the 3Π2-3Π2 subband of the (2, 3) band was resolved. ► Precise molecular constants of the levels involved are obtained. ► The molecular constants of c3Πu are improved.