Intermolecular interaction in proton-bound dimers.: Infrared photodissociation spectra of Rg–HOCO+ (Rg=He, Ne, Ar) complexes

Infrared photodissociation spectra of the proton-bound Rg–HOCO+ ionic complexes (Rg=He/Ne/Ar) have been recorded in the vicinity of the ν1 (OH stretch) vibration. The observed complexation-induced red shifts (Δν1) are 47, 120, and 704 cm−1 for the He, Ne and Ar containing species and correlate linearly with the proton affinity of the rare-gas atom. Weak transitions in the 100–220 cm−1 range to the blue of the ν1 fundamentals are assigned to combination bands of ν1 with the intermolecular stretching mode, νs. The geometries, vibrational frequencies and interaction energies of the Rg–HOCO+ complexes have been investigated by ab initio calculations at the MP2 level, and the results are in good agreement with the experimental data.