Ionic yield and dissociation pathways from soft X-ray double-ionization of alcohols

We present data from inner shell excitation and double-ionization of alcohols of interstellar interest, methanol and ethanol at energies around C 1s edge. The measurements were taken at the Brazilian Synchrotron Light Laboratory (LNLS), employing soft X-ray photons (100-310eV) from a toroidal grating monochromator (TGM) beamline. The experimental set up consists of a high vacuum chamber with a time-of-flight mass spectrometer TOF-MS. Mass spectra were obtained using coincidence techniques. Mean kinetic energies, abundances and dissociation pathways for each ionic pair in coincidence have been obtained from the analysis of the corresponding peak shapes and slopes observed in photoelectron photoion photoion (PE2PICO) coincidence mass spectra. The main dissociation channels of double ionized methanol were associated to the ions pairs H+ + COH+, H+ + CO+, H+ + CH2+ and H+ + CH+. In the case of double ionized ethanol, the main dissociation channels were associated to the ions pairs CH3+ + COH+, H+ + COH+, H+ + CH2+ and H+ + C2H2+. About 40% and 25% of the dissociation channels of doubly ionized methanol and ethanol, respectively, lead to the production of reactant COW ion, important for the formation of other organic molecules. (c) 2006 Elsevier B.V. All rights reserved.