Unusual photofragmentation mechanisms of chlorinated species elucidated by a combination of double and triple ionic coincidences spectra

BAVA, YANINA B.; BERRUETA MARTINEZ YANINA; CAVASSO FILHO REINALDO L.; ROMANO, ROSANA M.

Campinas

Congreso; 26th RAU- Anual Users Meeting LNLS/CNPEM; 2016

LNLS/CNPEM

Photofragmentation mechanisms of small molecular compounds after shallow- or coreelectron ionization can be determined by using coincidence techniques (Photoelectron-Photoion- Photoion-Coincidences, PE2PICO), as presented for example in reference 1 and references cited therein. In this work we discuss the importance of the combined study of the PE2PICO and PE3PICO spectra to understand some unusual photofragmentation mechanisms of chlorinated species, trichloroethylene (HClC=CCl2, 3CE), deuterotrichloroethylene (DClC=Cl2, D3CE) and tetrachloroethylene (Cl2C=CCl2, 4CE), after ionization of Cl 2p and C 1s electron.The studies were performed in the TGM and SGM beamlines at LNLS, with theexperimental station for gaseous samples and coincidence techniques (PEPICO, PE2PICO and PE3PICO) using a Wiley-Mac Laren time-of-flight mass spectrometer. The pressure of the sample inside the chamber was maintaied below 5.10-6 mbar, which guarantee the study of only unimolecular fragmentation mechanisms.Different fragmentation mechanisms were proposed by the analysis of the bidimensional PE2PICO spectra, being the most important Cl+/C2Cl2+/Cl and CCl2+/CCl2+ for 4CE, and Cl+/XC2Cl2+ and XC2Cl+/Cl2+ (with X =H or D) for 3CE and D3CE. However, some of the islands with positive slopes,as for example the H+/C+ coincidence presented in Figure 1, could not beinterpreted in terms of any fragmentation mechanisms of M2+. In these cases, theanalysis of the PE3PICO projections, also shown in Figure 1, are needed forthe correct evaluation of the PE2PICO spectra. Clearly, the fragments wereproduce after a triple ionization, giving H+, C+, Cl+ and neutral fragments.