Rotational analysis of the c3Πu–b3Πg system of P2

Abstract The rotationally resolved spectra of the c 3 Π u – b 3 Π g system of P 2 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 c 3 Π u ( υ =2) state, the Λ -doubling in the 3 Π 2 – 3 Π 2 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 c 3 Π u state and for the υ ″=2 and 3 levels in the b 3 Π g state of P 2 were derived.