First analysis of the ν5 band of DNO3 (deuterated nitric acid) in the 11 μm region

The infrared spectrum of DNO3 (deuterated nitric acid) was recorded at high resolution (0.0027 cm−1) in the 700-1400 cm−1 region on a Bruker IFS 120 HR Fourier transform spectrometer. The analysis of the ν5 band of DNO3 centred at 887.657 cm-1 which is mostly an A-type band, was performed making use of the ground state parameters achieved by Drouin et al. [Drouin BJ, Miller CE, Fry JL, Petkie DT, Helminger P, Medvedev IR. J Mol Spectrosc 2006;236:29-34]. The ν5 fundamental band is strongly perturbed because of the existence of the ν7+ν9 dark combination band at 882.21  cm-1. The 51 and 7191 energy levels of DNO3 are coupled through A and B type Coriolis resonances, and as a consequence, numerous lines from the ν7+ν9 dark combination band could be identified also. In this way about 1070 and 75 energy levels of the 51 and 7191 vibrational states, respectively, were satisfactorily reproduced by the energy levels calculation which account for the observed resonances. A reasonable estimation of the absolute line intensities for the ν5 band of DNO3 was performed using the ν5 transition operator from H14NO3. The spectrum also features the ν5+ν6−ν6, ν5+ν7−ν7 and ν5+ν9−ν9 hot bands located at 881.03, 882.61 and 884.45 cm−1, respectively.