Multireference CI Study of Excitation Energies and Potential Energy Surfaces of CH3F

Glauco F. Bauerfeldt, Hans Lischka

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Abstract

Vertical excitation energies for the eight singlet-excited electronic states 11E (2e → 3s), 21E (2e → 3p a1), 31E (2e → 3pe), 21A 1 (2e → 3pe), 11A2 (2e → 3pe), 31A1 (2pa1 → 3s), 4 1A1 (2pa1 → 3pl), and 4 1E (2pa1 → 3pe) of CH3F were investigated using the SA-MCSCF, MR-CISD, and MRCISD+Q approaches. Our results mostly confirm the experimental assignments but suggest some modifications for the main contribution to the maximum observed in the range from 12.5-14 eV. The dissociation channels for the production of fluorine atoms have been characterized. Potential energy curves for the dissociation of the CF bond under C3v symmetry restrictions were computed for all states mentioned above leading to the ground-state dissociation channel CH3(X 2A2″) + F(2P), the excited-state channels CH3(3s 2A1′) + F(2P) and CH3(3p 2A2″) + F(2P) and also to the ionic limit CH3+(1A1′) + F-(1S). All curves except the one for the ionic state show repulsive behavior. The search for a global minimum for the ionic state led to the structure H2CH+F- in the 3 1A′ state. It is strongly bound by 5.67 eV with respect to the ionic dissociation limit of F- + CH3+.

Original languageEnglish
Pages (from-to)3111-3118
Number of pages8
JournalJournal of Physical Chemistry A
Volume108
Issue number15
DOIs
StatePublished - Apr 15 2004

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