The microwave spectrum of the NF radical in the second electronically excited (b 1Σ+) state: Potentials of three low-lying states (X 3Σ−,a 1Δ,b 1Σ+)

Abstract

The pure rotational transition of the NF radical in the second electronically excited state, b 1Σ+, was detected by microwave spectroscopy. The NF radical was generated by dc-discharge through a mixture of NF3 and H2 at around 90 K. Six rotational transitions for v=0 and four for v=1 were observed in the 73–442 GHz region. In addition to the rotational and centrifugal distortion constants, the quadrupole coupling constant of the nitrogen nucleus of NF(b 1Σ+) was determined for the first time from the lowest two transitions of NF in the v=0 level. The spectrum of NF(a 1Δ) in the first vibrational excited state was also observed in order to derive highly accurate potential parameters for comparison with the data of NF(X 3Σ−,b 1Σ+).