J.-M. FLAUD, J. ORPHAL, Laboratoire de Photophysique Moléculaire, C.N.R.S., Bât. 350, Université Paris-Sud, 91405 Orsay Cedex, France; W. J. LAFFERTY, Optical Technology Division, NIST, Gaithersburg, MD 20899, U.S.A; M. BIRK AND G. WAGNER, Institute for Opto-electronics, DLR, 82234 Oberpfaffenhofen, Germany.
A ro-vibrational analysis of the C-type 8 fundamental band of 35ClONO2 as well as the hot band, 8 + 9 - 9, has been carried out using a Fourier-transform infrared spectrum of natural chlorine nitrate. This spectrum was recorded with a resolution of 0.00094~cm-1 at a temperature of 190~K. Accurate upper state constants have been determined for both bands including the following band centers: 0 ( 8) = 711.20763(9) and 0 ( 8+ 9 - 9) = 714.9050(12)~cm-1. These constants have been used, together with a transition moment operator which takes into account the observed Herman-Wallis effect, to successfully model the experimental spectrum. Moreover the constants of the 8191 state have been used to model the 8 + 9 band, allowing us to assign nearly 100 Q-branch transitions and, therefore, to determine the band center of the 8 + 9 band , 0 ( 8 + 9 )= 838.6269(15)~cm-1. Consequently we are able for the first time to obtain a precise band center of 9 : 0 ( 9) = 123.7219(20)~cm-1. Finally this establishes unambiguously that the band at 714.9~cm-1 previously attributed to 5 + 7 - 9 is actually the 8 + 9 - 9 hot band.