Electric-Field-Induced Perturbations in the Ultraviolet Spectra of Polyatomic Molecules; the 1B2 State of Benzonitrile

Abstract

We report the observation of an electric‐field‐induced perturbation in the 0–0 band of the π * ←π ( 1 B 2 ← 1 A 1 ) transition of benzonitrile (2738 Å). Strong nonlinear Stark effects are observed at fields as low as 0.5 kV/cm. Analysis of the observations allow determination of the dipole moment of the perturbing state ( 1.35±0.3 D ), the transition moment between the mutually perturbed excited states ( 1.0±0.5 D ) and the zero‐field separation of the perturbing states ( 0.01±0.01 cm −1 ). In addition the vibronic symmetry of the perturbing state is shown to be B 2. It is argued that the most likely perturbing state is the previously unobserved π * ←n ( 1 B 1 ) state.