Electron spin resonance investigations of 11B12C, 11B13C, and 1B12C in neon, argon, and krypton matrices at 4 K: Comparison with theoretical results

Abstract

The first spectroscopic study of the diatomic radical BC is reported which confirms previous theoretical predictions of a 4∑− electronic ground state. The nuclear hyperfine interactions (A tensors) obtained for 11B, 10B, and 13C from the electron spin resonance (ESR) measurements are compared with extensive ab initio CI calculations. The BC molecule is one of the first examples of a small high spin radical for such an in-depth experimental–theoretical comparison. The electronic structure of BC obtained from an analysis of the nuclear hyperfine interaction (hfi) is compared to that obtained from a Mulliken-type population analysis conducted on a CI wave function which yields Aiso and Adip results in good agreement with the observed values. The BC radical was generated by the laser vaporization of a boron–carbon mixture and trapped in neon, argon, and krypton matrices at 4 K for a complete ESR characterization. The magnetic parameters (MHz) obtained for 11B13C in solid neon are: g∥ =2.0015(3); g⊥ =2.0020(3); D(zfs)=1701(2); 11B: ‖A∥‖ =100(1); ‖A⊥‖ =79(1); 13C: ‖A∥‖ =5(2) and ‖A⊥‖ =15(1). Based on comparison with the theoretical results, the most likely choice of signs is that all A values are positive.