The far-infrared rotational spectrum of nitrous acid (HONO) and its deuterated species (DONO) studied by high-resolution Fourier-transform spectroscopy

In this paper, we present the first high-resolution (0.003 cm(-1)) absorption measurements of the pure rotational spectra of nitrous acid (trans- and cis-HONG) and its deuterated species (trans- and cis-DONO) in the far-infrared region between 40 and 150 cm(-1). The spectra were first assigned based on rotational constants from previous studies in the microwave and mid-infrared regions. New rotational and centrifugal distortion constants were determined for all four species. The accuracy of the principal rotational constants was improved, and several quartic and sextic (and even a few octic) centrifugal distortion constants were obtained for the first time. Synthetic spectra calculated using the new constants of this study reproduce the observed spectra very well. (c) 2005 Elsevier Inc. All rights reserved.