OH stretching vibrations in aromatic cations: IR/PIRI spectroscopy

This Letter presents a new technique (IR/PIRI) to investigate OH stretching vibrations of cations. In the IR/PIRI technique the MATI signals obtained for the electronic origin or a vibrational state of the ion are depleted by an IR laser if the frequency of the IR laser is in resonance with an OH stretching vibration of the cation. As an example, the resorcinol molecule is chosen. Two different isomers of this molecule are investigated. In combination with ab initio calculations and IR depletion spectroscopy performed for the electronic ground (S0) and electronically excited state (S1) of the neutral molecule all OH stretching vibrations of the different isomers in the S0, S1, and D0 states are interpreted.