Ionic photofragmentation of ClSO2NCO in the S 2p, Cl 2p and S 2s regions

ANGÉLICA MORENO BETANCOURT; LUCAS S. RODRÍGUEZ PIRANI; MARIANA GERONÉS; MAURICIO F. ERBEN; REINALDO L. CAVASSO FILHO; CARLOS O. DELLA VÉDOVA; ROSANA M. ROMANO

Campinas

Otro; 21ª Reunião Anual de Usuários (RAU), Laboratório Nacional de Luz Síncrotron; 2011

On the frame of a general project aimed to the elucidation of the photochemical and electronic properties of molecules containing the XSO2- group, with X = halogen,1 we present here the study of the electronic properties and the dynamic of the ionic photofragmentation of chlorosulfonyl isocyanate, ClSO2NCO, in the S 2p, Cl 2p and S 2s regions. A commercial sample of ClSO2NCO (Aldrich) was purified by repeated trap-to-trap distillations in vacuum. The purity of the compound was checked by means of the gas-phase FTIR spectra.2 The Total Ion Yield (TIY) spectra of ClSO2NCO in vapour phase were recorded in the TGM beamline at LNLS between 100 and 300 eV, using the vacuum chamber for gaseous samples. In this energy region, the spectrum could be divided into three parts, corresponding to excitation of S 2p, Cl 2p and S 2s electrons, respectively. Below the S 2p threshold, occurring at approximately 182.8 eV, the TIY spectrum presents a group of five well defined signals at 170.3, 171.6, 173.2, 174.2 and 175.6 eV and a shoulder at 176.9 eV. A single feature is observed at 208 eV, below the Cl 2p threshold at approximately 214.7 eV. The S 2s edge is also clearly observed in the TIY spectrum at 239 eV. The PEPICO spectra of ClSO2NCO were measured at every resonance and threshold energy and also below and above the resonances. Almost every possible cationic fragment of the parent molecule is observed in the spectra, although the relative abundances strongly depend on the excitation energy. The PEPICO spectrum taken at 110 eV, far below the first S 2p resonance, is dominated by a peak at 106 m/q, which corresponds to SO2NCO+. Also M+, ClSO2+, SO2+, SO+, NCO+, among others, are discernable in the spectra. For the fragments containing Cl or S atoms, the characteristic isotopic pattern is observed. As the excitation energy reaches the S 2p resonance region, the NCO+ and SO+ fragments become more abundant, while at S 2p threshold energy the S+ ion dominates the spectrum. In the PEPICO spectrum measured at 214.7 eV, at the Cl 2p threshold, the Cl+ fragment is the most intense peak. Two-dimensional PEPIPICO spectra for the correlation between one electron and two positive ions were recorded at the same photon energies than PEPICO spectra. Several double coincidences were detected in the spectra, revealing different fragmentation mechanisms from a double charged molecular ion. The most important pairs of ions detected in coincidences were Cl+/SO2NCO+, NCO+/SO2+, O+/Cl+, O+/S+, and N+/S+.