Rotamers of m-aminophenol cation studied by mass analyzed threshold ionization spectroscopy and theoretical calculations

The vibrationally resolved spectra of selected rotamers of m-aminophenol have been recorded by mass analyzed threshold ionization spectroscopy in connection with two-color resonant two-photon excitation scheme. The adiabatic ionization energies of the cis and trans rotamers are 61 460 ± 5 and 61 734 ± 5 cm−1, respectively. The frequencies of modes 1 (breathing) and 18a (in-plane CH bending) are measured to be 744 and 1097 cm−1 for the cis, and 736 and 1104 cm−1 for the trans rotamer, respectively. This indicates that different orientation of the OH with respect to the NH2 substituent only slightly influences these two modes.