Laser excitation spectroscopy of the B 1Σ+u(O+u)←a 3Πg(O+g) transition of Cd2: Vibrational analysis and rotational structure

Abstract

The B 1Σ+u←a 3Πg transition of Cd2 (natural abundance) and 114Cd2 has been observed by laser excitation spectroscopy and analyzed. By exciting the Cd2 B←a transition in the visible (560≤λ≤730 nm) while monitoring B 1Σ+u→X 1Σ+g (bound→free) emission in the ultraviolet (∼270–310 nm), more than 40 red-degraded vibrational bands were recorded. Analysis of the spectrum has yielded vibrational constants for both the a 3Πg and B 1Σ+u states: ωe″=153.6±4.0 cm−1, ωe″xe″=0.52±0.06 cm−1, ωe′=105.3±1.0 cm−1, and ωe′xe′=0.44±0.03 cm−1. In addition, ΔRe≡ReB−Rea was determined to be 0.31±0.03 Å. Rotational structure has been partially resolved for 114Cd2 bands in the 620–655 nm and 719–723 nm regions, and the spontaneous emission lifetime of the a 3Πg state and the rate constant for quenching of Cd2 (a 3Πg) by collisions with background Cd atoms have been determined to be 8.6±2.5 μs and (2.2±0.3)×10−13 cm3 s−1, respectively. Also, analysis of the B→X emission (Condon internal diffraction) spectra produced when specific B 1Σ+u vibrational levels are populated has yielded ReX−ReB=0.95±0.02 Å.