Improvement of the Spectroscopic Constants of the PF(A3Π) State and Assignment of the PF(A–X) Transition Dipole Function

Abstract

High-resolution laser-excitation spectra were acquired for the v′=3–7 levels of the PF(A3Π0,1,2←X3Σ−) transition from PF(X3Σ−) molecules generated in a discharge flow reactor. These results were combined with lower resolution excitation spectra for the v′=8–11 levels and with existing high-resolution data in the literature for v′=0 and 1 to assign improved spectroscopic constants for PF(A3Π0,1,2). The abnormal vibrational energy level spacings for all spin components of the PF(A3Π) state are evidence for a homogeneous interaction with another 3Π state. The Λ-doublet separation in the PF(3Π0) substate increases with vibrational level, which is taken as evidence for interaction with the PF(b1Σ+) state. Laser-induced fluorescence spectra from individual v′=0–5 levels were used to obtain vibrational band intensities of the A–X transition. The strong dependence of the transition dipole on the r-centroid is consistent with the reduction in the radiative lifetimes with increasing v′ level. The similarity between the isovalent PF(A3Π) and SO(A3Π) states is noted and the bond dissociation energy of PF(X3Σ−) is discussed.