Optical–optical double resonance spectroscopy of the Cl2 1g(1D) ion-pair state

Abstract

The 1g(1D) ion-pair state of Cl2 has been analyzed by optical–optical double resonance using the 1g(1D)–A 3Π(1u)–X 1Σg+ photoexcitation sequence. We recorded the spectra for both the 35–35Cl2 and 37–35Cl2 isotope species and established the absolute vibrational numbering of the 1g(1D) state from the isotope difference. A set of molecular parameters was derived from the data set in the 0≤v≤6 range, and used to construct the potential function of the 1g(1D) state. We interpreted the Ω-doubling of the 1g(1D) state in terms of the heterogeneous coupling with an unknown 0g+(1D) state correlating to the same ionic asymptote. The potential function of the 0g+(1D) state is predicted in a pure precession analysis.