Accounting for the Torsional Splitting in the ν5 and 2ν9 Bands of Nitric Acid

✍ Scribed by L.H. Coudert; A. Perrin

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 844 KB
• Volume: 172
• Category: Article
• ISSN: 0022-2852
• DOI: 10.1006/jmsp.1995.1184

✦ Synopsis

In an attempt to account for the large-amplitude torsional (\nu_{9}) mode of nitric acid, a formalism is set up, based on an internal-axis-method-like approach previously developed for high-barrier tunneling problems. This formalism is applied to the calculation of the tunneling-rotationalvibrational energy of the interacting (v_{9}=2) and (v_{5}=1) vibrational states and accounts for the rotational dependence of the tunneling splitting and for the strong Coriolis and Fermi resonances between these two vibrational states. With the help of this formalism, it is shown that the effects of the large-amplitude motion may be very different depending on the way the rotational states are clustered. For large (K_{a}) values, shifts of about (0.001 \mathrm{~cm}^{-1}) are predicted, while splittings of roughly the same value occur for large (K_{c}) values. This formalism is used to carry out a simultaneous analysis of the microwave data relevant to the two vibrational states (Goyette et al., J. Mol. Spectrosc. 167, 365-374, 1994) and of the infrared transitions belonging to the (2 \nu_{9}) and (\nu_{5}) bands (Perrin et al., J. Mol. Spectrosc. 157, 112-121, 1993). The frequency of the microwave transitions and the wavenumber of the infrared transitions are satisfactorily reproduced and it is possible to point out the effects of the large-amplitude motion in the latter data set. ©o 1995 Academic Press. Inc.