High-resolution study of the a2Π–X2Σ+ band system of BH+

Abstract

The 0–0, 1–1 and 1–0 bands of the A²Π–X²Σ⁺ transition of BH⁺ have been photographed with high resolution in emission from a hollow cathode discharge lamp. Accurate molecular constants for ¹¹BH⁺ are derived, the principal constants (error limits 3σ) being: for the A²Π state, B_e= 11.7987 (9) cm^–1, α_e= 0.4543 (11) cm^–1, r_e= 1.243 97 (5)Å and ΔG_1/2= 2152.83₂(2) cm^–1; for the X²Σ⁺ state, B_e= 12.6177 (10) cm^–1, α_e= 0.4928 (10) cm^–1, r_e= 1.202 92 (5)Å and ΔG_1/2= 2396.34₇(2) cm^–1. The strongest branches for ¹⁰BH⁺ are identified and the isotopic shifts are shown to be in good agreement with the calculated values. The possibility of finding BH⁺ in astrophysical sources is discussed.