Structures and vibrations of phenol(NH3)2−4 clusters

Abstract

Vibronic spectra of PhOH(NH3)n clusters with n=2–4 have been obtained by resonant two-photon ionization, recorded at the mass channels of the fragment ions (NH3)nH+. The PhOH(NH3)2–4 spectra show long progressions of at least one low frequency vibration pointing to different S0 and S1 geometries along this coordinate. In addition, the vibronic bands of the n=2 cluster are split into two components. A tunneling motion is discussed, which may be responsible for these splittings. To get more information about the structure of PhOH(NH3)2 in the electronic ground state, IR–UV double resonance spectroscopy has been applied. Possible geometries for the n=2–4 clusters are considered based on a comparison between the experimental data and theoretical results from ab initio calculations, performed at the Hartree–Fock and second-order Møller–Plesset perturbation theory level.