Binding energies of carbazole⋅S van der Waals complexes (S=N2, CO, and CH4)

Abstract

Mass-selective ground-state vibronic spectra of molecular van der Waals complexes carbazole⋅S, S=N2, CO, and CH4, were measured by stimulated emission pumping followed by resonant two-photon ionization of the vibrationally hot complexes. S0-state vibrational modes were accessed from ≊200 cm−1 up to the ground-state dissociation limit D0(S0) of the van der Waals bond. Above D0, efficient vibrational predissociation of the complexes occurs, allowing accurate determination of the van der Waals dissociation energies as 627.2±7.9 cm−1 for N2, 716.5±29.8 cm−1 for CO, and 668.6±15.1 cm−1 for CH4. In the S1 excited state, the van der Waals binding energies increase to 678.5±8.0, 879.2±29.9, and 753.8±15.2 cm−1, respectively. The relative increases upon electronic excitation are about 8% and 13% for N2 and CH4, similar to the analogous rare gases Ar and Kr. For CO, the relative increase of van der Waals binding energy is 23%. The differences are primarily due to electrostatic interactions.