Vibrational Structure and Vibronic Coupling in the Carbon 1s Photoelectron Spectra of Ethane and Deuteroethane

Authors

Tor Karlson, University of Bergen
Leif J. Sæthre, University of Bergen
Knut J. Børve, University of Bergen
Nora Berrah, Western Michigan University
Edwin Kukk, University of Oulu
John D. Bozek, Lawrence Berkeley National Laboratory, University of California
Thomas X. Carroll, Keuka College
T. Darrah Thomas, Oregon State UniversityFollow

Date of this Version

2001

Comments

Published in J. Phys. Chem. A, Vol. 105, No. 32, 2001.

Abstract

The carbon 1s photoelectron spectrum of ethane, C₂H₆, has been measured at a photon energy of 329 eV and an instrumental resolution of 70 meV. The spectrum shows a rich vibrational structure which is resolved using least-squares fits to the data. Only C-H stretching and CCH bending modes contribute significantly to the spectrum. The lack of excitation of the C-C stretching mode is explained in terms of changes in hybridization at the spectator carbon. To investigate the possibility of incomplete localization of the core hole, the spectra of C₂H₆ and C₂D₆ were measured at higher experimental resolution (35 meV). The spectra are accurately fit by a model based on ab initio calculations of the vibrational energies and the geometry changes following ionization, and including vibronic coupling of the two degenerate, localized hole states. A small splitting on the order of 10-20 meV is found for the ²A_2u and ²A_1g core-ionized states.