The b1Σ+(b0+) → X3Σ−(X10+,X21) and a1Δ(a2) → X21 transitions of AsBr

Emission spectra of the b1Σ+(b0+) → X3Σ−(X10+,X21) and a1Δ(a2) → X21 transitions of AsBr have been measured in the near-infrared spectral region with a Fourier-transform spectrometer. The arsenic bromide radicals were generated in fast-flow systems by reaction of arsenic vapor (Asx) with bromine and were excited by microwave-discharged oxygen. The most prominent features in the spectrum are the Δv = +1,0,−1, and −2 band sequences of the b1Σ+(b0+) → X3Σ−(X10+) transition in the range 11 700-12 700 cm−1. With lower intensities, the Δv = 0 and −1 sequences of the b1Σ+(b0+) → X3Σ−(X21) sub-system show up in the same range. Further to the red, between 6000 and 6700 cm−1, the Δv = 0, +1, and −1 sequences of the hitherto unknown a1Δ(a2) → X21 transition are observed. Analyses of medium- and high-resolution spectra have yielded improved molecular constants for the X10+, X21, and b0+ states and first values of the electronic energy and the vibrational constants of the a2 state.