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Fragmentation processes following core excitation in acetylene and ethylene by partial ion yield spectroscopy
Journal of Chemical Physics
  • Maria Novella Piancastelli, Uppsala University
  • Wayne C. Stolte, University of Nevada, Las Vegas
  • Gunnar Ohrwall, MAX-lab, Lund University
  • S-W Yu, Lawrence Berkeley National Laboratory
  • D. Bull, Lawrence Berkeley National Laboratory
  • K. Lantz, Lawrence Berkeley National Laboratory
  • Alfred S. Schlachter, Lawrence Berkeley National Laboratory
  • Dennis W. Lindle, University of Nevada, Las Vegas
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Partial ion yield spectroscopy provides a very detailed picture of fragmentation processes following core excitation in isolated molecules. We exploit this potential in the analysis of decay processes following C1s→π and C1s→Rydberg excitations in ethylene and acetylene. We show that the relative intensity of spectral features related to the excitation to empty molecular orbitals or to Rydberg states is a function of the time variation of the fragmentation process. Namely, we see an intensity increase in the Rydberg states compared to the molecular orbitals as the fragmentation process becomes more extensive, a result attributable to the diffuse nature of the Rydberg virtual orbitals, which makes spectator decay more likely than participator decay. Therefore, the number of dissociative final states that can be reached from Rydberg excitation is higher than for excitation to empty molecular orbitals. In acetylene, we obtain the first direct evidence of the presence of a ơ* excitation embedded in the Rydberg series. The formation of the fragment H2+ in ethylene occurs following a recombination process, while in acetylene it is related to excess vibrational energy stored in the intermediate state. Furthermore, we can use the enhancement in channels corresponding to doubly charged species as an indication for the presence of shape resonances.

Copyright American Institute of Physics, used with permission
Publisher Citation
Piancastelli, M. N., Wayne C. Stolte, G. Öhrwall, S-W. Yu, D. Bull, K. Lantz, A. S. Schlachter, and Dennis W. Lindle. "Fragmentation processes following core excitation in acetylene and ethylene by partial ion yield spectroscopy." The Journal of chemical physics 117 (2002): 8264.
Citation Information
Maria Novella Piancastelli, Wayne C. Stolte, Gunnar Ohrwall, S-W Yu, et al.. "Fragmentation processes following core excitation in acetylene and ethylene by partial ion yield spectroscopy" Journal of Chemical Physics Vol. 117 Iss. 18 (2002) p. 8264 - 8269
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