IR multiple photon dissociation spectroscopy of MO2 + (M = V, Nb, Ta).

A laser vaporization cluster source is coupled to the Fourier-transform ion cyclotron resonance mass spectrometer beamline of the free-electron laser for intracavity experiments. Gas phase metal ions and their oxides (VO2 +, NbO2 +, and TaO2 +) are formed and spectroscopically characterized using IR multiple-photon dissociation spectroscopy via loss of atomic oxygen and overcoming fragmentation energies of 3 eV-6 eV. The signal is observed for all MO2 + fundamental modes: the symmetric and anti-symmetric ν1 and ν3 stretch modes in the 900 cm-1-1000 cm-1 range and the ν2 bending mode in the 300 cm-1-450 cm-1 range. A remarkable substructure is observed for the bending vibration, which is at least partly due to the rovibrational substructure.