Electronic spectrum of boron dichloride. theoretical study of vibronic levels of the ground and first excited states

• Published in: Journal of molecular structure Vol. 1224; p. 129206
• Main Authors: Gharaibeh, Mohammed, Al-Shami, Bayenah, Helal, Wissam
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15-01-2021
• Subjects: Ab-initio; Electronic spectrum; Linear-bent transition; Renner-teller effect; Electronic spectrum; Ab-initio; Linear-bent transition; Renner-teller effect
• ISSN: 0022-2860; 1872-8014
• DOI: 10.1016/j.molstruc.2020.129206

•Electronic transition between the two renner-teller components of a 2Π state.•PESs of the ground and excited states calculated using high-level ab-initio methods.•Variational method is applied to calculate vibronic levels of the interacting states.
As expected by the Walsh diagram of AB2 molecules, the electronic spectrum of BCl2 radical involves bent-linear transitions between the ground and first excited states that form the two degenerate components of the 2Π electronic state of the linear molecule. A high level ab-initio theoretical study on BCl2 radical has been undertaken by constructing potential energy surfaces (PES) using the coupled-cluster singles and doubles with perturbative triples (CCSD(T)) with aug-cc-pVQZ for boron and aug-cc-pV(Q + d)Z for chlorine atoms. Vibronic energy levels were determined variationally, from the obtained PES, up to ~35,000 cm−1 above the relative minima of the ground and excited states. Low-lying vibrational levels of the ground and first excited electronic states were obtained, which showed a very complex structure which is known to be as a result of large Renner-Teller vibronic coupling. For the most abundant isotopologue, 11B35Cl2, the ground state fundamental frequencies are; ω10= 696.0 cm−1, ω20= 281.0 cm−1 and ω30=981.8 cm−1. For the same isotopologue, vibrational fundamentals of the excited state were estimated by fitting Σ vibronic levels to be ω10= 463.2 cm−1, ω20= 281.7 cm−1 and ω30=1245.1 cm−1.