Spin-spin and spin-rotation constants of NBr(X3Σ−)

Rotationally resolved emission spectra of the 0-0 band of the b1Σ+-X3Σ− transition in NBr were obtained from the FBr + HN3 chemiluminescence flame. The spectra revealed two strong branches, SR and QP, and two much weaker branches, OP and QR, with the QQ branch unobserved. The resolution of the spectrometer was not sufficient to resolve the two naturally occurring isotopes of Br. Analysis of the rotational lines yields the following set of molecular constants: ν00 = 14 812 ± 2, B′0 = 0.4782 ± 0.0037, B″0 = 0.4529 ± 0.0036, λ = 12.38 ± 0.11, and γ = −0.023 ± 0.018 (units in cm−1).