High-level ab initio calculation of the rotation-vibration energies in the c {sup 1}A{sub 1} state of methylene, CH{sub 2}

Journal Article · Thu Nov 14 04:00:00 EST 1996 · Journal of Physical Chemistry

DOI:https://doi.org/10.1021/jp961993j· OSTI ID:420683

Bunker, P R ^[1]; Jensen, P ^[2]; Yamaguchi, Yukio; Schaefer, III, H F ^[3]

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1. Steacie Inst. for Molecular Science, Ottawa (Canada)
2. Bergische Universitaet-Gesamthochschule Wuppertal, Wuppertal (Germany)
3. Univ. of Georgia, Athens, GA (United States)

For the third excited electronic state (c- {sup 1}A{sub 1}) of the methylene radical, CH{sub 2}, we calculate the electronic potential energy surface using a high-level ab initio method and the rotation-vibration energies using a variational technique with a large rotation-vibration basis set. The potential energy surface is calculated at a carefully selected grid of 48 nuclear geometries that cover all types of combination of stretching and bending deformations to energies more than 20000 cm{sup -1} above that the equilibrium configuration. We fit an analytical function, in which we vary 23 parameters, through the points and find that the state is almost linear with an equilibrium angle of 172.7{degree} and a barrier to linearity of only 6 cm{sup -1}. It is well-known that theoretical treatments of higher lying states in the same symmetry are substantially tedious and complicated. The basis set used [TZ3P(2f,2d)+2diff] was triple-{zeta} plus triple polarization with two sets of higher angular momentum functions and two sets of diffuse functions. We have used the variational MORBID procedure to calculate the rotation-vibration energies. Because of the peculiar shape of the bending part of the potential surface, some very large bending force constants f{sub 0}{sup (i)} are obtained, and this has necessitated the use of very large basis sets in the MORBID calculation in order to achieve acceptable convergence. 17 refs., 2 figs., 4 tabs.

• DOE Contract Number: FG05-94ER14428
• OSTI ID: 420683
• Journal Information: Journal of Physical Chemistry, Journal Name: Journal of Physical Chemistry Journal Issue: 46 Vol. 100; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
66 PHYSICS
99 GENERAL AND MISCELLANEOUS
CALCULATION METHODS
ELECTRONIC STRUCTURE
METHYLENE RADICALS
MOLECULAR MODELS
MOLECULAR ORBITAL METHOD
PHYSICAL CHEMISTRY
THEORETICAL DATA