Optical–optical double resonance with two dye lasers: Rotational analysis of the E 2Σ–B2Σ system of Ca35Cl

A complete rotational analysis of the E 2Σ–B 2Σ system of CaCl has been accomplished using two tunable dye lasers. The first cw laser is tuned to a known B 2Σ–X 2Σ transition to produce a finite concentration of molecules in a particular quantum state. Subsequently, a second pulsed dye laser is used to record the E 2Σ–B 2Σ excitation spectrum from this state prepared level. The method vastly simplifies an otherwise congested molecular spectrum. The data are combined with previous microwave measurements on the X 2Σ state and optical data on the B 2Σ–X 2Σ system to give the following molecular constants (cm−1). Uncertainties are 95% confidence limits in the last digit.