The Spectroscopy of Formaldehyde: III. Out-of-Plane Potentials and Geometry Optimizations for Singlet States
✍ Scribed by M.R.J. Hachey; P.J. Bruna; F. Grein
- Publisher
- Elsevier Science
- Year
- 1996
- Tongue
- English
- Weight
- 286 KB
- Volume
- 176
- Category
- Article
- ISSN
- 0022-2852
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✦ Synopsis
Out-of-plane potentials and optimized geometries for excited singlet states of formaldehyde, including n,p*, s,p*, p,p*, n,3s, and n,3p, were obtained by multireference CI methods. The 1 (n,p*) and 1 (s,p*) states were found to be nonplanar, with out-of-plane angles of 34.5Њ and 42.1Њ, respectively. Agreement with the experimental geometry and energy of 1 (n,p*) is good, and even the inversion barrier is well reproduced. The 1 (n,3s), 1 (s,p*), and 1 (p,p*) (mixed with n 2 ) states were found to have minima on different sections of the S 2 surface, separated from one another by low barriers of 0.2 to 0.7 eV. This causes the n r 3s Rydberg transition to be perturbed by 1 (s,p*) and 1 (p,p*). At nonplanar geometries, 1 (s,p*) mixes heavily with 1 (p,p*); therefore, the p r p* band system, which may be observable from the higher vibrational levels of the ground state, is expected to be significantly perturbed. The C ˜R X ˜system, recently reassigned to n r 3p z , should be perturbed not only by 1 (n,3p y ), as previously suggested, but also by 1 (p,p*) through the n 6 (CH 2 rocking) mode. Furthermore, the Q 6 potential of 1 (n,3p z ) is expected to interact with 1 (n,s * CH ). The D ˜R X system, assigned to n r 3p y , is predicted to be perturbed by 1 (p,p*), as well as by 1 (s,p*) through the out-of-plane bending mode.