Three lowest-lying electronic states of NH{sub 2}

Journal Article · Thu Sep 23 04:00:00 EDT 1999 · Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory

DOI:https://doi.org/10.1021/jp991455h· OSTI ID:20000080

Yamaguchi, Yukio; Hoffman, B C; Stephens, J C; Schaefer, III, H F

The three lowest-lying electronic states, {tilde X} {sup 2}B{sub 1}, {tilde A} {sup 2}A{sub 1}, and {tilde B} {sup 2}B{sub 2}, as well as the lowest linear {sup 2}II stationary point of NH{sub 2} have been investigated systematically using ab initio electronic structure theory. The SCF, CASSCF, CISD, CASSCF-SOCI, CCSD, and CCSD(T) levels of theory have been employed to determine total energies, equilibrium structures, and physical properties including dipole moments, harmonic vibrational frequencies, and infrared intensities of NH{sub 2}. According to the instability analysis of the reference SCF wave functions, physical properties of the three lowest-lying equilibrium states of NH{sub 2} may be obtained correctly in the variational sense with all wave functions employed in this study. The lowest linear stationary point ({sup 2}II) possesses two distinct imaginary vibrational frequencies along the bending coordinate, indicating a strong Renner-Teller interaction. The predicted geometries and physical properties of the two lowest states of NH{sub 2} are in good agreement with available experimental results. At the CCSD(T) level of theory with the largest basis set, the triple-{zeta} (TZ) plus triple polarization with two sets of higher angular momentum and two sets of diffuse functions [TZ3P(2f,2d)+2diff], the {tilde A} {sup 2}A{sub 1} state of NH{sub 2}, with a large bond angle of 144.9{degree}, is predicted to lie 32.1 kcal/mol (1.39 eV, 11,200 cm{sup {minus}1}) above the ground state. This is in excellent agreement with the experimental {sub 0} value of 31.80 kcal/mol (1.379 eV, 11,122.6 cm{sup {minus}1}). The second excited state ({tilde B} {sup 2}B{sub 2}) possesses an acute bond angle of 49.3{degree} and is determined to lie 100.1 kcal/mol (4.34 eV, 35,000 cm{sup {minus}1}) above the ground state. The classical (and effective) barriers to linearity for the {tilde X} {sup 2}B{sub 1} and {tilde A} {sup 2}A{sub 1} states were predicted to be 11,870 (12,310) cm{sup {minus}1} and 720 (790) cm{sup {minus}1}, which are again in good accord with the experimentally estimated values of 12,024 cm{sup {minus}1} ({tilde X} {sup 2}B{sub 1}) and 730 cm{sup {minus}1} ({tilde A} {sup 2}A{sub 1}).

• Research Organization: Univ. of Georgia, Athens, GA (US)
• Sponsoring Organization: US Department of Energy
• DOE Contract Number: FG02-97ER14748
• OSTI ID: 20000080
• Journal Information: Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory, Journal Name: Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory Journal Issue: 38 Vol. 103; ISSN 1089-5639; ISSN JPCAFH
• Country of Publication: United States
• Language: English

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