NEW ACCURATE WAVENUMBERS OF H35Cl+ AND H37Cl+ ROVIBRATIONAL TRANSITIONS IN THE v=0_1 BAND OF THE 2_ STATE.

Abstract

HCl$^+$ is a key intermediate in the interstellar chemistry of chlorine. It has been recently identified in space from {it Herschel's} spectrafootnote{M. De Luca et al., {it Astrophys. J. Lett.} {bf 751}, L37 (2012)} and it has also been detected in the laboratory through its optical emissionfootnote{W. D. Sheasley and C. W. Mathews, {it J. Mol. Spectrosc.} {bf 47}, 420 (1973)}, infraredfootnote{P. B. Davies, P. A. Hamilton, B. A. Johnson, {it Mol. Phys.} {bf 57}, 217 (1986) } and mm-wave spectrafootnote{H. Gupta, B. J. Drouin, and J. C. Pearson, {it Astrophys. J. Lett.} {bf 751}, L37 (2012) }. Now that {it Hershchel} is decomissioned, further astrophysical studies on this radical ion will likely rely on ground-based observations in the mid-infrared. We have used a difference frequency laser spectrometer coupled to a hollow cathode discharge to measure the absorption spectrum of $rm{H}^{35}rm{Cl}^+$ and $rm{H}^{37}rm{Cl}^+$ in the $v=0-1$ band of the $^2Pi$ state with Dopppler limited resolution. The accuracy of the individual measurements ($sim$ 10 MHz (3$sigma$)) relies on a solid state wavemeter referenced to an iodine-stabilized Ar$^+$ laser. The new data are being fit using the CALPGM software from JPL, and the current status will be presented.