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S. WANG, Y. J. SHI, B. SIMARD, Z. J. JAKUBEK, M. BARNETT, Steacie Institute for Molecular Sciences, National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario, K1A 0R6, Canada; C-P. LIU, Department of Chemistry, National Tsing Hua University, 101, Sec 2 Kuang-Fu Road, Hsinchu, Taiwan, 30043, R. O. C.; K. MÜLLER-DETHLEFS, Department of Chemistry, The University of York, Heslington, York, YO10 5DD, UK.
The rotationally resolved nonresonant two-photon mass analyzed threshold ionization (MATI) spectra and zero kinetic energy (ZEKE) photoelectron spectra of CH2CO+ and CD2CO+ are presented. The MATI and ZEKE spectra of CH2CO+ are dominated by the totally symmetric modes
4 (C=C stretch) and
2 (C=O stretch), with weaker excitation of
3 (CH2 scissor), while those of CD2CO+ are dominated by approximately equally intense
2,
3, and
4. This is consistent with the theoretical calculations of Takeshita, which indicate a strong coupling of
3 and
4 modes of CD2CO+ in the ground state. In addition, weak excitations to the nontotally symmetric vibrations
5 (CH2 wag),
6 (C=C=O linear bend) and
9 (C=C=O linear bend) are also observed in the MATI spectra of both isotopomers. Rotational structure is dominated by very strong
Ka=\pm1 manifolds with two orders of magnitude weaker
Ka=+3 features. Analysis of the ZEKE spectra provides the ionization potentials (77538.8\pm2 cm-1 for CH2CO and 77533.7\pm2 cm-1 for CD2CO) and rotational constants for the ground states of both ketene cations.