Vibronic analysis of the [image omitted] band system of BNB.

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 [image omitted] electronic transition of the linear BNB radical. The vibronic band system is complicated by spin-orbit interaction and the Renner-Teller effect in the [image omitted] 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 [image omitted] = 96 cm-1, 2 [image omitted] = 202 cm-1; [image omitted] = 846 cm-1, [image omitted] = 322 cm-1, ε' = +0.45 and 2 [image omitted] = 1201 cm-1 for 11B14N11B. [ABSTRACT FROM AUTHOR]