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Ab initio calculations on the quenching of excited lithium atom by molecular hydrogen. I
Author(s) -
Matsumoto Shiro,
Mizutani Kimiko,
Sekiguchi Atsushi,
Yano Takakazu,
Toyama Masayuki
Publication year - 1986
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560290411
Subject(s) - conical intersection , excited state , chemistry , atomic physics , ab initio , wave function , potential energy , basis set , diatomic molecule , potential energy surface , diabatic , conical surface , polarization (electrochemistry) , ground state , hydrogen atom , molecular physics , computational chemistry , physics , molecule , quantum mechanics , geometry , group (periodic table) , density functional theory , organic chemistry , adiabatic process , mathematics
MCSCF calculations were performed on the two lowest states of the LiH 2 system, using a basis set of double‐zeta‐plus‐polarization quality. The characters of the wave functions in the region of the conical intersection of the potential energy surfaces were investigated in some detail. The depth of the minimum on the à 2 B 2 surface was estimated to be 0.46 eV. The frequency of the a 1 vibration at the center of the conical intersection was 3.76 X 10 13 sec −1 . Under the symmetry of the nuclear geometry lower than C 2 v in the immediate neighborhood of the center of the intersection, the upper state was characterized by a 3 a ′ natural orbital by which the more distant H is bonded to Li, while in the lower state the nearer H is bonded to Li. Thus, the process of the nonadiabatic transition caused by a nuclear motion of b 2 symmetry is visualized as a smooth bond‐preserving process, and is expected to occur with high probability. For the correct description of the states in this region, MCSCF functions comprising limited CSF 's were inadequate, and an additional process of nonorthogonal CI was required.