Ab initio study of cyanogen

The X̃ 1Σ g +, ã3Σu +, B̃ 1Δu, and C̃ 1Π u states

C. E. Dateo, Michel Dupuis, W. A. Lester

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Abstract

An ab initio multiconfiguration Hartree-Fock (MCHF) study of the X̃ 1Σg +, a ̃3Σ, u +1Δu, and C̃ 1Πu states of cyanogen (C2N2) is presented. Equilibrium structures, harmonic vibrational frequencies, excitation energies, and dissociation energies have been calculated and found to be in semiquantitative agreement with available experimental data. This study confirms the π→π* character of C2N23Σu +) and C2N2 (B̃ 1Δu), and the n→;π* character of C2N2 (C̃ 1Πu) near their equilibrium structures. Configuration mixing among the n and π electrons is needed to correct the broken symmetry description given by the Hartree-Fock (HF) method, and leads to a qualitatively correct representation of these states. For C2N23Σu +) and C2N2 (B̃ 1Δ u), the harmonic force constants show a strong through-bond interaction which is due to the dominance of the charge transfer configuration +NCCN-. For C2N2 (C̃1Πu) the trans-bending vibrational mode and the cis-bending mode lead to different Renner-Teller splittings: the lower 1A′ state most likely has a slightly trans-bent minimum energy structure. The calculated harmonic stretching frequencies of C2N 2 (C̃ 1Πu) are v1 (sym. CN str.)=2145 cm-1, v2 (CC str.)=989 cm-1, and v3 (asym. CN str.)=1789 cm-1.

Original languageEnglish
Pages (from-to)265-272
Number of pages8
JournalJournal of Chemical Physics
Volume83
Issue number1
Publication statusPublished - 1985

Fingerprint

cyanogen
Excitation energy
Vibrational spectra
Stretching
Charge transfer
harmonics
Electrons
configurations
energy
vibration mode
broken symmetry
charge transfer
dissociation
excitation
electrons
interactions

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

Cite this

Ab initio study of cyanogen : The X̃ 1Σ g +, ã3Σu +, B̃ 1Δu, and C̃ 1Π u states. / Dateo, C. E.; Dupuis, Michel; Lester, W. A.

In: Journal of Chemical Physics, Vol. 83, No. 1, 1985, p. 265-272.

Research output: Contribution to journalArticle

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abstract = "An ab initio multiconfiguration Hartree-Fock (MCHF) study of the X̃ 1Σg +, a ̃3Σ, u + B̃ 1Δu, and C̃ 1Πu states of cyanogen (C2N2) is presented. Equilibrium structures, harmonic vibrational frequencies, excitation energies, and dissociation energies have been calculated and found to be in semiquantitative agreement with available experimental data. This study confirms the π→π* character of C2N2 ({\~a} 3Σu +) and C2N2 (B̃ 1Δu), and the n→;π* character of C2N2 (C̃ 1Πu) near their equilibrium structures. Configuration mixing among the n and π electrons is needed to correct the broken symmetry description given by the Hartree-Fock (HF) method, and leads to a qualitatively correct representation of these states. For C2N2 ({\~a} 3Σu +) and C2N2 (B̃ 1Δ u), the harmonic force constants show a strong through-bond interaction which is due to the dominance of the charge transfer configuration +NCCN-. For C2N2 (C̃1Πu) the trans-bending vibrational mode and the cis-bending mode lead to different Renner-Teller splittings: the lower 1A′ state most likely has a slightly trans-bent minimum energy structure. The calculated harmonic stretching frequencies of C2N 2 (C̃ 1Πu) are v1 (sym. CN str.)=2145 cm-1, v2 (CC str.)=989 cm-1, and v3 (asym. CN str.)=1789 cm-1.",
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