The {sup 3}A{sub 2}, {sup 1}A{sub 2}, {sup 3}B{sub 2}, and {sup 1}B{sub 2} electronic states of CH{sub 2}: Small bond angle states

Journal Article · Sat Feb 01 04:00:00 EST 1997 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.473323· OSTI ID:463519

Yamaguchi, Y; Schaefer, III, H F ^[1]

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1. Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia 30602 (United States)

Molecular structures with very small bond angles are a curiosity in chemistry. The two triplet ({sup 3}A{sub 2} and {sup 3}B{sub 2}) and two singlet ({sup 1}A{sub 2} and {sup 1}B{sub 2}) excited states of CH{sub 2} have been investigated systematically using {ital ab initio} electronic structure theory. For these four states total energies and physical properties including geometries, dipole moments, harmonic vibrational frequencies, and associated infrared intensities were determined with the single and double excitation configuration interaction (CISD) method using four different basis sets. It is confirmed in this study that the four states of CH{sub 2} all have bent structures with longer CH bond lengths and smaller bond angles than the four lower-lying ({tilde X}, {tilde a}, {tilde b}, and {tilde c}) states of CH{sub 2}. At the CISD optimized geometries single point energies were determined with complete active space self-consistent-field (CASSCF) and CASSCF second-order configuration interaction (SOCI) levels of theory. For the triplet excited states single point energies were also determined employing coupled cluster with single and double excitations (CCSD) and CCSD with perturbative triple excitations methods. At the CISD level with the largest basis set, the triple zeta plus triple polarizations with two sets of higher angular momentum and two sets of diffuse functions basis set [TZ3P(2f,2d)+2diff], the bond angles were predicted to be 40.6{degree} ({sup 3}A{sub 2}), 46.1{degree} ({sup 1}A{sub 2}), 76.3{degree} ({sup 3}B{sub 2}), and 81.3{degree} ({sup 1}B{sub 2}), while the dipole moments were determined to be 2.35 ({sup 3}A{sub 2}), 2.26 ({sup 1}A{sub 2}), 1.69 ({sup 3}B{sub 2}), and 1.60 debye ({sup 1}B{sub 2}), respectively. (Abstract Truncated)

• DOE Contract Number: FG05-94ER14428
• OSTI ID: 463519
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 5 Vol. 106; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
BOND ANGLE
CONFIGURATION INTERACTION
ELECTRONIC STRUCTURE
EXCITED STATES
HARMONICS
HYDROCARBONS
POLARIZATION
RADICALS
SELF-CONSISTENT FIELD
coupled cluster calculations