Optical–optical double resonance spectroscopy of Cl2: First observation and analysis of the 0−g(3P1) ion-pair state and the lower-lying B′ 3Π(0−u) valence state

Abstract

The perturbation facilitated optical–optical double resonance technique allows access to the 0−g(3P1) ion-pair state through the A 3Π(1u) v=9 intermediate state where the A 3Π(1u) ∼B′ 3Π(0−u) interaction occurs: 0−g(3P1) –{A 3Π(1u) ∼B′ 3Π(0−u) }–X 1Σ+g. Molecular constants of the 0−g(3P1) state are derived from 197 transitions in the 0≤v′≤15 and 9≤J′≤47 range, and a Rydberg–Klein–Rees (RKR) potential based on these constants is given. The dispersed fluorescence spectra of the 0−g(3P1) –B′ 3Π(0−u) system are used to establish the absolute vibrational numbering of the 0−g(3P1) state, and also to characterize the new B′ 3Π(0−u) state in view of the Franck–Condon factor consideration.