JET-COOLED HIGH RESOLUTION INFRARED LASER SPECTROSCOPY OF Kr-H2O IN THE REGION OF THE BENDING MODE OF H2O

The high sensitivity of our experimental setup (SPIRALES) [1] which couples an external cavity quantum cascade laser tunable from 1620 to 1690 \wn to a pulsed jet enabled the recording of a series of rovibrational transitions of Kr-H$_{2}$O van der Waals (vdW) complex. As for the Ar-H$_{2}$O complex [2], the barriers to internal rotation in the Kr-H$_{2}$O complex states are comparable to the H$_{2}$O rotational constants and so the H$_{2}$O subunit behaves like a nearly free internal rotor [3]. The quantum number K is used for describing the projection of J onto the vdW axis, with K = 0 for $\Sigma$, K = 1 for $\Pi$, etc. A previous jet-cooled microwave study [4] evidenced that the ground vibrational state involves 2 internal rotor states corresponding to different spin modifications, namely a para state $\Sigma($0$_{00}$) and an ortho state $\Sigma($1$_{01}$). The present work reports the observation of two new bands around 1634.5 \wn and 1659.7 \wn which can be interpreted according to a pseudo-atomic model. By analogy with Ar-H$_{2}$O bands observed in the same regions [2], the Kr-H$_{2}$O ones are tentatively assigned to para $\Pi$(1$_{11}$) $\leftarrow$ $\Sigma$(0$_{00}$) and ortho $\Pi$(2$_{12}$) $\leftarrow$ $\Sigma$(1$_{01}$) transitions, respectively, confirmed by the presence of Q branches. The ortho band displays strongly unequal spacings characteristic of a Coriolis coupling between $\Sigma$ and $\Pi$ states in vibrational excited states. \begin{wrapfigure}{c}{0pt} \includegraphics[scale=0.3]{H2O_Kr_1658_1661_Fig_abstractURB.eps} \end{wrapfigure} Moreover the high resolution achieved with the SPIRALES set-up allowed the observation of several isotopes of Kr. The analysis of these two bands and further investigations in the 1580-1620 \wn region are undergoing. References : [1] P. Asselin , A. Potapov, A. C. Turner, V. Boudon, L. Bruel, M.-A. Gaveau, M. Mons. PCCP 19, 17224-17232 (2017). [2] X. Liu , Y. Xu. J. Mol. Spectr. 301, 1-8 (2014). [3] R.C. Cohen , K . L . Busarow , Y. T. Lee, R. J. Saykally. JCP, 92, 169-177 (1990). [4] J. Van Wijngaarden, W. Jäger. Mol. Phys. 98, 19,1575-1588 (2000)