The ground-state infrared spectrum of four isotopic forms of barium monohydride (BaH)

Abstract

The infrared spectrum of four isotopic forms of gas-phase barium monohydrides, 138BaH (71.7%), 137BaH (11.3%), 136BaH (7.8%), and 135BaH (6.4%) in natural abundance in their ground electronic state ( 2Σ +) have been observed using a diode laser spectrometer. A number of transitions of 134BaH (2.4%) were also observed, but insufficient data were accumulated to allow a good analysis. As a result of coupling between the unpaired electron and the overall rotation each individual transition appears as a doublet. The wavenumber of seven transitions of the ν=1←0, six of the ν=2← 1 band and eight of the ν=3←2 band have been measured to ±0.001 cm −1. The spin-rotational splitting (γ splitting), which is of the order of 0.2 cm −1, was easily resolved and higher-order correction terms determined.