The Cd_2 and Zn_2 van der Waals dimers revisited. Correction for some molecular potential parameters

摘要

The excitation spectrum of Cd_2 van der Waals complexes produced in a free-jet supersonic expansion beam was studied using Ar as carrier gas and a pulsed dye-laser as light source. A well resolved structure of vibrational bands arising from transitions between X0_g~+ (~1#SIGMA#_g~+) and 0_u~+ (~3#PI#_u) states were observed. Owing to the properties of the molecular beam we were able to obtain spectra with different progressions originating from higher (v">=1) vibrational levels of the ground state. The 'hot band' frequencies made possible - for the first time - a direct determination of the ground state parameters of the molecule. We verified our earlier results of Cd_2 molecular spectra that were recently questioned by Helmi et al. [1]. We have also critically revised the previously reported, estimated bond-lengths of Cd_2 and Zn_2, demonstrating an excellent experiment-theory agreement of results of Refs. [2] and [3] and Refs. [4] and [5], respectively.