VUV photoionization and dissociation of o-nitrotoluene: Experimental and theoretical insights

The photoionization and dissociation of o-nitrotoluene have been studied by using tunable vacuum ultraviolet (VUV) mass spectrometer, in which ion time-of-flight (TOF) mass spectra are recorded as a function of the photon energy in the range of 9.0-15.0 eV. The ionization energy of o-nitrotoluene and appearance energies for its fragment ions C7H6NO+, C6H6N+, C7H7+, C6H7+, C6H5+ and C5H5+, are determined to be respective 9.43, 9.71, 12.11, 11.01,12.15, 12.38 and 12.88 eV from the photoionization efficiency spectra. With the help of experimental and theoretical results, four photodissociation channels have been proposed: C7H6NO+ + OH, C6H6N+ + CO + OH, C7H7+ + NO2, and C5H5+ + C2H2 + NO2. The dominant channel is found to be C7H6NO+ + OH, followed by C6H6N+ + CO + OH. All of these channels occur via isomerization prior to dissociation except for C7H7+ + NO2.