Rotational spectrum of BiBr

Abstract

The microwave absorption spectra of Bi 79Br and Bi 81Br have been measured in the 65–100 GHz region. Frequencies of rotational transitions (υ, J + 1) ← (υ, J) in the 0 + electronic ground state with J = 26,27 and 35–39, and in the vibrational state υ = 0–11 can be fitted to the expression: ν = 2[ Y 01 + Y 11(υ + 1 2 ) + Y 21(υ + 1 2 ) 2] ( J + 1) + 4 Y 02( J + 1) 3. The results for the Dunham coefficients are: Y 01 = 1295.5609(12) MHz, Y 11 = −3.97809(18) MHz, Y 21 = 2.303(18) kHz, Y 02 = −220.26(45) Hz for Bi 79Br, and: Y 01 = 1272.3406(12) MHz, Y 11 = −3.87164(16) MHz, Y 21 = 2.225(14) kHz, Y 02 = −212.31(45) Hz for Bi 81Br. From these results we have deduced the value for the equilibrium distance r e, for the potential constants a 0 and a 1, and for the vibrational constants ω e and ω eχ e. The molecular constants of BiBr are almost the same as of TIBr, the situation found also for BiI and TII.