Vibronic analysis of the band system of BNB

Abstract

Gas-phase electronic spectra of the BNB radical and its isotopomers have been measured in a supersonic molecular beam in the visible spectral region. A mass-selective resonant two-colour two-photon ionization technique coupled to a laser ablation source was employed. Ab initio calculations on the geometries, energies and vertical electronic excitations have been carried out using the Becke 3-parameter Lee–Yang–Parr (B3LYP) method, the spin restricted coupled cluster (RCCSD(T)) approach and the multireference configuration-interaction (MRCI) theory for the linear BNB, BBN, and cyclic B2N isomers. The spectra are assigned as the electronic transition of the linear BNB radical. The vibronic band system is complicated by spin–orbit interaction and the Renner–Teller effect in the 2Πg state. The vibronic structure of the transition has been analysed using the Pople–Hougen theoretical model and the calculated potential curves along the bending coordinate. The resulting spectroscopic constants are = 96 cm−1, 2 = 202 cm−1; = 846 cm−1, = 322 cm−1, ε′ = +0.45 and 2 = 1201 cm−1 for 11B14N11B.