The application of a VUV Fourier transform spectrometer and synchrotron radiation source to measurements of: I. The β(9,0) band of NO

Abstract

State-of-the-art models of the vacuum ultraviolet (VUV) absorbing properties of the atmosphere call for absorption cross sections with detail on the scale of the Doppler widths. As a consequence, spectroscopic data at resolving powers of the order of 106 are needed. To meet these requirements in the vacuum ultraviolet region, we have used the VUV Fourier transform spectrometer from Imperial College, London, at the synchrotron radiation facility at Photon Factory, KEK, Japan, to measure photoabsorption cross sections of NO from 195 to 160 nm, and of O2 from 185 to 175 nm. The analysis of the β(9,0) band (B 2Πr–X 2Πr) of NO provides accurate rotational line positions and term values. Molecular constants of the B(9) 2Π level are T0=54 205.097±0.012 cm−1, A=45.320±0.021 cm−1, Bυ=1.016 72±0.000 16 cm−1, Dυ=(10.61±0.32)×10−6 cm−1, and AD=0.001 22±0.000 11 cm−1. The rotational line strengths and the branching ratios are also presented. The band oscillator strength is obtained as f=2.65×10−4.