Intermolecular bending levels in an open-shell diatom–diatom complex: Infrared spectroscopy and model calculations of the OH–N2 complex

Abstract

A theoretical framework has been developed to describe the bending levels associated with an intermolecular potential of moderate anisotropy between an open-shell diatom and a diatom partner, such as OH–CO or OH–N2. The model explicitly allows for coupling between the electronic and spin angular momenta of the open-shell OH radical and the vibrational angular momentum arising from intermolecular bending motion of the complex. The energies and wave functions of the intermolecular bending levels for the OH–N2 complex have been computed based on a dipole–quadrupole interaction. The model is used to interpret the infrared spectrum of the linear OH–N2 complex in the OH overtone region, which has been recorded by detecting the OH fragments from vibrational predissociation. The pure OH overtone band at 6973.54(2) cm−1 and several combination bands, which involve the simultaneous excitation of OH stretching and geared bending modes, have been observed, analyzed, and assigned within the context of the model. In addition, the time evolution and quantum state distribution of the OH fragments yield the lifetime for vibrationally activated OH–N2 of 30±4 ns and an upper limit for the ground state binding energy of OH–N2, D0⩽277 cm−1.