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Journal of Chemical Physics / Volume 93 / Issue 11

J. Chem. Phys. 93, 8021 (1990); http://dx.doi.org/10.1063/1.459331 (8 pages)

The low‐lying electronic states of protonated C2, CCH+

Wolfram Koch1 and Gernot Frenking2

1IBM Deutschland GmbH, Heidelberg Scientific Center, Institute for Supercomputing and Applied Mathematics, Tiergartenstr. 15, D‐6900 Heidelberg, Federal Republic of Germany
2Fachbereich Chemie, Universität Marburg, Hans‐Meerweinstr., D‐3550 Marburg, Federal Republic of Germany

(Received 14 December 1989; accepted 6 August 1990)

Complete active space self‐consistent field (CASSCF) and multireference configuration interaction (MRCI) calculations have been performed on the energetically lowest lying electronic states of protonated C2 (CCH+), using extended Gaussian basis sets of the general contraction type.The 3Π state has been unequivocally identified as the ground state of CCH+, followed by 3Σ−, which is 0.34 eV higher in energy. The lowest linear singlet state is 1Π. However, this state is not stable towards Renner–Teller distortion. A bent structure of 1A′ symmetry is 0.21 eV lower in energy than 1Π and represents the most stable singlet CCH+ cation, 0.91 eV higher than X 3Π. A 1Δ and two 1Σ+ states have also been studied. They are 1.13, 1.54, and 3.55 eV higher in energy than the 3Π ground state. The activation barriers of the degenerate hydrogen migration for ground state CCH+, which can occur on the 3A″ or the 3A′ surface, are computed to be 1.27 and 2.43 eV, respectively, with C2v transition structures. For the lowest singlet CCH+ cation, the 1A1 C2v structure is not a transition state, but represents a very shallow energy minimum, 0.26 eV higher than the 1A′ minimum. The saddle point has Cs geometry and lies 0.30 and 0.04 eV above the 1A′ and 1A1 minima. Our results are compared to earlier theoretical data, obtained at significantly lower levels of ab initio theory, and with the experimentally known translational energy spectrum of CCD+.

KEYWORDS and PACS

Keywords

INTERSTELLAR MOLECULES, ELECTRONIC STRUCTURE, MOLECULAR IONS, CONFIGURATION INTERACTION, AB INITIO CALCULATIONS, HYDROCARBONS

PACS

  • 31.15.V-

    Electron correlation calculations for atoms, ions and molecules

  • 33.20.Wr

    Vibronic, rovibronic, and rotation-electron-spin interactions

  • 98.38.Bn

    Atomic, molecular, chemical, and grain processes

  • 98.38.Er

    Interstellar masers

  • 98.58.Bz

    Atomic, molecular, chemical, and grain processes

  • 98.58.Ec

    Interstellar masers

ARTICLE DATA

Digital Object Identifier
http://dx.doi.org/10.1063/1.459331

PUBLICATION DATA

ISSN

0021-9606 (print)  
1089-7690 (online)

For access to fully linked references, you need to log in.
    See for example: W. W. Duley and D. A. Williams, Interstellar Chemistry (Academic Press, New York, 1984).

    R. Krishnan, M. J. Frisch, R. A. Whiteside, J. A. Pople, and P. v. R. Schleyer, J. Chem. Phys. 74, 4213 (1981JCPSA6000074000007004213000001).

    J. Almlöf and P. Taylor, J. Chem. Phys. 86, 4070 (1987JCPSA6000086000007004070000001).

    Quoted in M. Dupuis and B. Liu, J. Chem. Phys. 73, 337 (1980JCPSA6000073000001000337000001).


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