THE ROTATIONAL SPECTRUM OF CHLORINE NITRATE (ClONO$_2$): $\nu_6$ AND THE $\nu_5$/$\nu_6\nu_9$ DYAD

Author Institution: Institute of Physics, Polish Academy of Sciences, Al. Lotnikow; 32/46, 02-668 Warszawa, Poland; Department of Physics, Pittsburg State University, Pittsburg, KS 66726; Department of Physics, Wright State University, Dayton, OH 45435; Department of Physics, University of South Alabama, Mobile, Al 36688; Department of Physics, The Ohio State University, Columbus,; OH 43210Chlorine nitrate is an important stratospheric molecule and analyses of extensive measurements of rotational transitions in the ground state and $\nu_9$ (120 cm$^{-1}$)}, 363-378 (1997).}, the 2$\nu_9$/$\nu_7$ dyad (262 cm$^{-1}$)}, 8-14 (2002).}, and the 3$\nu_9$/$\nu_7\nu_9$ dyad (361 cm$^{-1}$)}, 150-152 (2003).} have already been reported. The available experimental data for ClONO$_2$ 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. \vspace{0.2cm} The new spectrum allowed an improvement in the spectroscopic constants for the ground state and $\nu_9$, as well as more confident assignment of rotational transitions in higher vibrational states. Application of the AABS package for $Assignment and Analysis of Broadband Spectra$}}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 $\nu_6$ (435 cm$^{-1}$) and of the $\nu_5$/$\nu_6\nu_9$ dyad (551 cm$^{-1}$) have now been completed for both $^{35}$ClONO$_2$ and $^{37}$ClONO$_2$. In the parent isotopologue the $\nu_5$ and $\nu_6\nu_9$ 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