Photodissociation spectroscopy of Ca+-formaldehyde

We have carried out photodissociation spectroscopy studies of Ca+(H2CO). The work is supported by electronic structure calculations of the ground and low-lying excited states of the complex. Our results show that Ca+(H2CO) is bound in a C-2v Ca-O-CH2 ground-state equilibrium geometry with a bond dissociation energy of D-e'(Ca-OCH2)=0.9+/-0.2 eV. We have assigned five distinct molecular absorption bands of the complex that correlate with Ca+-based 3d and 4p<--4s radiative transitions. The absorption bands show clear vibrational resonance structure with partially resolved rotational substructure. Spectroscopic constants are, for the most part, in good agreement with ab initio model predictions. The experimental data give quantitative information about the bonding interactions for electronically excited states of different valence and molecular-orbital character. Results for Ca+(H2CO) are compared with previous results from our lab on the analogous Mg+(H2CO) complex [J. Chem. Phys. 117, 6970 (2002)]. (C) 2003 American Institute of Physics.