Experimental and theoretical study on proton tunneling in jet-cooled 9-hydroxyphenalenone-CO2 van der Waals complex

The fluorescence excitation, dispersed fluorescence, and hole-burning spectra of the 9-hydroxyphenalenone (9HPO)-CO 2 1:1 complex have been measured to investigate the effects of the van der Waals interaction on proton tunneling in the So state. The S 1 -S 0 electronic origin is only 4 cm - 1 red-shifted with respect to that of the monomer, suggesting that proton tunneling occurs in both the So and S 1 states of the 9HPO-CO 2 complex, although the tunneling splittings have not been observed in the excitation spectrum. The structure of the observed complex and its tunneling potential for the So state of 9HPO have been theoretically investigated by using the reaction surface Hamiltonian method. The intermolecular interaction significantly changes the shape of two dimensional potential energy surface along the reaction coordinates, and slightly decreases the tunneling splitting in the zero-point level.