Study on the photoionization and dissociative photoionization of ortho-, meta-, para-bromofluorobenzenes using VUV synchrotron radiation

Highlights: • The first study of photoionization of BrFPh under synchrotron radiation. • The ionization and dissociation energies of o-, m-, p-BrFPh are studied. • The DFT calculation was associated with photoionization MS experiments. Bromofluorobenzene(BrFPh) is one of the major volatile atmospheric pollutants. In this paper, using the VUV synchrotron radiation as the excitation source, the photoionization time of flight mass spectra of ortho-, meta-, para-BrFPh moleclues were recorded and the mass spectra illustrated that BrFPh molecule would be ionized into ${C_6{H}_{4}BrF}^{+}$ and then dissociate into ${C_6{H}_{4}F}^{+}$ and Br atom under the synchrotron radiation. Then the photoionization efficiency (PIE) curves of each parent ions and fragment ions were obtained by plotting the ion intensity versus photon energy. And the photoionization energies of three isomers of BrFPh molecules were determined to be 9.10 eV, 9.16 eV, 8.98 eV. Meanwhile, the photodissociation energies of o-, m-, p-${C_6{H}_{4}BrF}^{+}$ ions were determined to be 3.71 eV, 3.50 eV and 3.63 eV, respectively. Furthermore, the photoionization and photodissociation energies of them were also calculated based on DFT via B3LYP/6–311++G basis set. The theoretical results are in excellent agreement with the experimental values, and could provide important theoretical support for the experimental analysis of the photoionization and dissociative photoionization process of BrFPh molecules.