The 3d Rydberg ({sup 3}A{sub 2}) electronic state observed by Herzberg and Shoosmith for methylene

Journal Article · Sun Jun 01 04:00:00 EDT 1997 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.473935· OSTI ID:496671

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)

In 1959 and 1961 Herzberg and Shoosmith reported the vacuum ultraviolet spectrum of the triplet state of CH{sub 2}. The present study focuses on a characterization of the upper state, the 3d Rydberg ({sup 3}A{sub 2}) state, observed at 1415 {Angstrom}. The theoretical interpretation of these experiments is greatly complicated by the presence of a lower-lying {sup 3}A{sub 2} valence state with a very small equilibrium bond angle. {ital Ab initio} electronic structure methods involving self-consistent-field (SCF), configuration interaction with single and double excitations (CISD), complete active space (CAS) SCF, state-averaged (SA) CASSCF, coupled cluster with single and double excitations (CCSD), CCSD with perturbative triple excitations [CCSD(T)], CASSCF second-order (SO) CI, and SACASSCF-SOCI have been employed with six distinct basis sets. With the largest basis set, triple zeta plus triple polarization with two sets of higher angular momentum functions and three sets of diffuse functions TZ3P(2f,2d)+3diff, the CISD level of theory predicts the equilibrium geometry of the 3d Rydberg ({sup 3}A{sub 2}) state to be r{sub e}=1.093{Angstrom} and {theta}{sub e}=141.3deg. With the same basis set the energy (T{sub e} value) of the 3d Rydberg state relative to the ground ({tilde X}{sup 3}B{sub 1}) state has been determined to be 201.6kcalmol{sup {minus}1} (70500cm{sup {minus}1}) at the CCSD (T) level, 200.9{sub 2}kcalmol{sup {minus}1}(70270cm{sup {minus}1}) at the CASSCF-SOCI level, and 200.8{sub 9}kcalmol{sup {minus}1}(70260cm{sup {minus}1}) at the SACASSCF-SOCI level of theory. These predictions are in excellent agreement with the experimental T{sub 0} value of 201.95kcalmol{sup {minus}1}(70634cm{sup {minus}1}) reported by Herzberg. {copyright} {ital 1997 American Institute of Physics.}

• DOE Contract Number: FG05-94ER14428
• OSTI ID: 496671
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 21 Vol. 106; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
ABSORPTION SPECTRA
CONFIGURATION INTERACTION
METHYLENE RADICALS
RYDBERG STATES
SELF-CONSISTENT FIELD
ULTRAVIOLET SPECTRA