| Autor: |
Trofimov, A. B., Trofimov, A.B., Gromov, E. V., Gromov, E.V., Moskovskaya, T. E., Moskovskaya, T.E., Schirmer, J. |
| Předmět: |
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| Zdroj: |
Journal of Chemical Physics; 10/22/2000, Vol. 113 Issue 16, 6 Charts |
| Abstrakt: |
The group of three lowest singlet C 1s-excited states of formaldehyde H[sub 2]CO is studied theoretically. The equilibrium geometries are determined at the restricted open-shell Hartree-Fock (ROHF) level and refined total energies are obtained using the multireference configuration interaction (MRCI) approach. In agreement with an earlier prediction [Chem. Phys. 122, 9 (1988)] the second lowest singlet state, [sup 1]B[sub 2], is characterized by a doubly excited, "two particle-two hole" (2p-2h), configuration C 1s,n→π[sup *2]. Our calculations predict that H[sub 2]CO in the [sup 1]B[sub 2](2p-2h) state has a stable pyramidal equilibrium structure with a barrier to inversion of 0.28 eV, the valence angle being close to 107°. The calculated length of the CO bond is 1.390 Å. The [sup 1]B[sub 2](2p-2h) state is shown to be also bound with respect to all possible dissociation and rearrangement processes. The lowest predicted dissociation energy for the [sup 1]B[sub 2] state (H[sub 2]CO[sup *]→H[sub 2]+CO[sup *] reaction) is 0.29 eV (6.69 kcal/mol). The rationalization of the great stability of the [sup 1]B[sub 2](2p-2h) state is the similarity of its electronic structure to that of the first singly-excited state [sup 2]A[sup ″](n) of nitroxyl radical H[sub 2]NO·. The neighboring states [sup 1]B[sub 1](C 1s→π[sup *]) and [sup 1]A[sub 1](C 1s→3s) are characterized within the same framework. Spectroscopic implications and possibilities for the experimental identification of the [sup 1]B[sub 2](2p-2h) state are discussed. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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