Fragmentation of Methanol Molecules after Core Excitation and Core Ionization Studied by Negative-Ion/Positive-Ion Coincidence Experiments

Antti Kivimäki; Christian Stråhlman; Robert Richter; Rami Sankari

doi:10.1021/acs.jpca.7b11250

Fragmentation of Methanol Molecules after Core Excitation and Core Ionization Studied by Negative-Ion/Positive-Ion Coincidence Experiments

J Phys Chem A. 2018 Jan 11;122(1):224-233. doi: 10.1021/acs.jpca.7b11250. Epub 2017 Dec 28.

Authors

Antti Kivimäki^{1

2}, Christian Stråhlman^{3

2}, Robert Richter⁴, Rami Sankari²

Affiliations

¹ Nano and Molecular Systems Research Unit, University of Oulu , P.O. Box 3000, 90014 Oulu, Finland.
² MAX IV Laboratory, Lund University , P.O. Box 118, 22100 Lund, Sweden.
³ Malmö University , 20506 Malmö, Sweden.
⁴ Elettra-Sincrotrone Trieste , Area Science Park, 34149 Trieste, Italy.

PMID: 29237124
DOI: 10.1021/acs.jpca.7b11250

Abstract

We have studied the fragmentation of the methanol molecule after core excitation and core ionization by observing coincidences between negative and positive ions. Five different negative ions (H^-, C^-, CH^-, O^-, and OH^-) were observed at both the C 1s and O 1s edges. As negative ion formation occurs after resonant and normal Auger decay of core-hole states, it is necessarily linked with the release of positively charged fragments. Our data show that such fragmentation can happen in many different ways: We found approximately 30 negative-ion/positive-ion/positive-ion coincidence (NIPIPICO) channels. All involve only singly charged positive ions. Fragmentation channels leading to atomic ions are the most probable, but positive molecular ions are also frequently found in the context of anion formation. Coincidence yields as a function of photon energy were determined for the most intense NIPIPICO channels. Adding together the data measured at different photon energies, we could also verify the occurrence of four-ion coincidences, which involved one negative ion (H^- or O^-) and three positive ions.