Theoretical evidence for a bound doubly-excited 1B2(C 1s,n→π*2) state in H2CO below the C 1s ionization threshold
| Autor: | Alexander B. Trofimov, E. V. Gromov, Jochen Schirmer, T. E. Moskovskaya |
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| Rok vydání: | 2000 |
| Předmět: | |
| Zdroj: | The Journal of Chemical Physics. 113:6716-6723 |
| ISSN: | 1089-7690 0021-9606 |
| Popis: | The group of three lowest singlet C 1s-excited states of formaldehyde H2CO 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, 1B2, is characterized by a doubly excited, “two particle–two hole” (2p–2h), configuration C 1s,n→π*2. Our calculations predict that H2CO in the 1B2(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 A. The 1B2(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 1B2 state (H2CO*→H2+CO* reaction) is 0.29 eV (6.69 kcal/mol). The rationalization of the great stability of the ... |
| Databáze: | OpenAIRE |
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