Excitation spectrum of the A0+(5 3P1), B1(5 3P1)←X0+(5 1S0) transitions in the CdHe van der Waals molecule: Spectroscopic characterization of the X0+, A0+, and B1 electronic energy states

Abstract

The first observation of an excitation spectrum of the A0+(5 3P1), B1(5 3P1)←X0+(5 1S0) transitions in the CdHe van der Waals molecule is reported. A continuous molecular-jet-expansion beam of CdHe seeded in helium was crossed with a pulsed-laser beam produced by a Nd:YAG laser-pumped-dye laser. The dye laser frequency was doubled using a KDP-C crystal and tuned to a frequency in the vicinity of the 5 3P1↔5 1S0 resonance transition in atomic cadmium (λres≈3262.0 Å). The assignment of vibrational bands was obtained with the aid of rigorous computer simulation of the A0+←X0+ and B1←X0+ transitions. The analysis of the excitation spectrum yielded potential parameters of the molecule: De″(X0+)=14.2 cm−1, ωe″(X0+)=9.6 cm−1, ωe″xe″(X0+)=1.63 cm−1 for the ground state, and De′(A0+)=41.2 cm−1, ωe′(A0+)=20.0 cm−1, ωe′xe′(A0+)=2.4 cm−1 as well as De′(B1)=6.1 cm−1, ωe′(B1)=3.6 cm−1, and ωe′xe′(B1)=0.53 cm−1 for the excited states. From a simulation procedure the differences between equilibrium internuclear separations ΔR=Re″(X0+)−Re′(A0+)=−1.50 Å and ΔR=Re″(X0+)−Re′(B1) =+0.12 Å were also obtained. The results were subjected to the LeRoy–Bernstein method to evaluate the C6/R6 long-range potential parameters for the X0+ and A0+ energy states.