Z. KISIEL, E. BIALKOWSKA-JAWORSKA, Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warszawa, Poland; R. A. H. BUTLER, Department of Physics, Pittsburg State University, Pittsburg, KS 66726; D. T. PETKIE, Department of Physics, Wright State University, Dayton, OH 45435; P. HELMINGER, Department of Physics, University of South Alabama, Mobile, Al 36688; F. C. DE LUCIA, Department of Physics, The Ohio State University, Columbus, OH 43210.

Chlorine nitrate is an important stratospheric molecule and analyses of extensive measurements of rotational transitions in the ground state and nu9 (120 cm-1), the 2 nu9/ nu7 dyad (262 cm-1), and the 3 nu9/ nu7 nu9 dyad (361 cm-1) have already been reported. The available experimental data for ClONO2 have been extended by a new FASSST spectrum recorded between 118-378 GHz at greater sensitivity and resolution than hitherto and on a more pure sample.


The new spectrum allowed an improvement in the spectroscopic constants for the ground state and nu9, as well as more confident assignment of rotational transitions in higher vibrational states. Application of the AABS package for Assignment~ and~ Analysis~ of~ Broadband~ Spectra\footnoteZ.Kisiel, PROSPE - Programs for ROtational SPEctroscopy, http://info.ifpan.edu.pl/ kisiel/prospe.htm was crucial in keeping track of the transitions already assigned and rapid extension of datasets for new states. The analyses of the relatively isolated nu6 (435 cm-1) and of the nu5/ nu6 nu9 dyad (551 cm-1) have now been completed for both 35ClONO2 and 37ClONO2. In the parent isotopologue the nu5 and nu6 nu9 states are found to be 4.124652(6) cm-1 apart and to be connected by a sufficiently strong Coriolis interaction to give rise to measurable interstate transitions and to perturbed hyperfine splitting patterns.