Accurate multireference configuration interaction calculations on the lowest ¹Σ⁺ and ³Π electronic states of C₂, CN⁺, BN, and BO⁺

Journal Article · Sun Jan 01 00:00:00 EST 1995 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.469399· OSTI ID:1490336

Peterson, Kirk A. ^[1]

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1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

In this study, using a series of correlation consistent basis sets from double to quintuple zeta in conjunction with large internally contracted multireference configuration interaction (CMRCI) wave functions, potential energy functions have been computed for the X¹Σ⁺_g and a ³Π_u states of C₂ and the 1 ¹Σ⁺ and 1 ³Π states of CN⁺, BN, and BO⁺. By exploiting the regular convergence behavior of the correlation consistent basis sets, complete basis set limits have been estimated that led to accurate predictions for the electronic excitation energies, dissociation energies, equilibrium bond lengths, and harmonic vibrational frequencies. The 1 ¹Σ⁺ states of CN⁺ and BO⁺ are predicted to be the electronic ground states of these species with predicted equilibrium excitation energies (T_e) to the low-lying a ³Π states of 880±100 cm^-1 and 5000±200 cm^-1, respectively. A ³Π ground state of BN is predicted with an excitation energy to the low-lying a ¹Σ⁺ state of just 190±100 cm^-1. Identical calculations on the singlet–triplet splitting of C₂ yielded a prediction of 778 cm^-1 for T_e, which was just 62 cm^-1 above the experimental value. Accurate equilibrium bond lengths and fundamental frequencies are also predicted for BN, BO⁺, and the a ³Π state of CN⁺. Dipole moment functions have been computed by CMRCI for the ground and excited electronic states of the three heteronuclear diatomics, and these have been used to derive accurate microwave and infrared transition probabilities for these species. A dipole moment in v=0 of 5.42 D is calculated for the X¹Σ⁺ state of BO⁺, which should lead to an intense microwave spectrum. While the X ³Π ground state of BN is predicted to have a very weak infrared spectrum, this species should be observable in the microwave region since the predicted μ₀ is 1.98 D. Lastly, both the microwave and infrared spectra of X ¹Σ⁺ CN⁺ should be of moderate intensity.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: AC05-76RL01830; FG06-89ER75522
• OSTI ID: 1490336
• Report Number(s): PNL-SA-24357
• Journal Information: Journal of Chemical Physics, Vol. 102, Issue 1; ISSN 0021-9606
• Publisher: American Institute of Physics (AIP)
• Country of Publication: United States
• Language: English

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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY