Infrared spectroscopy of the NO3 radical from 2000 to 3000 cm−1

Abstract

The present paper reports high-resolution spectroscopic study of the 14NO3 radical in the 2000–3000 cm−1 region, where eight E′-A2′ bands from the ground state are observed. Three bands at 2206, 2246, and 2377 cm−1 are analyzed for the first time, and assigned to the ν1+3ν4, 2ν2+2ν4, and ν3+3ν4 bands, respectively. Bands at 2024, 2155, 2518, and 2585 cm−1 are reassigned to the ν1+ν3, 2ν3, ν1+ν3+ν4, and 2ν3+ν4 bands, respectively, by adopting the new ν3 vibrational frequency of 1055 cm−1 lower than the previous ν3=1492 cm−1. The band at 2902 cm−1 is observed for the first time and assigned to the ν1+ν3+2ν4 band which is the ν1 combined band with the 1927 cm−1 band. Band intensities observed in the 2000–3000 cm−1 region are attributed to the intensity borrowing from the B̃2E′–X̃2A2′ electronic transition through the vibronic interaction. Although the ν3 fundamental band has not been observed due to the cancelation of vibrational intensity and borrowed intensity, the 2ν3 band becomes stronger than ν3 by a factor of more than 50. Perturbation effects are recognized for the bands observed except for the 2206 cm−1 and 2377 cm−1 bands, and are analyzed by taking into account the Coriolis interaction in the most cases. However, the 2024 cm−1 band is free from the Coriolis interaction, and the v1–v3 interaction is incorporated in the analysis, leading to the 2ν1 frequency of 2008.8 cm−1, which is close to the energy value of 2010 cm−1 observed by a laser induced fluorescence study.