NEW EXPERIMENTAL DATA OF THE WATER VAPOR ABOVE ${\sim} 25000 cm^{-1}$ BY CW-CRLAS

Author Institution: Laboratoire de Spectrom\'etrie Physique, Universit\'e Joseph FourierThe Cavity RingDown Laser Absorption Spectroscopy (CRLAS or CRDS) technique is a unique tool for probing weakly absorbing molecular species. High resolution (Doppler-limited broadening) is achievable in the blue-UV energy region by intracavity frequency doubling a CW laser source (here a Ti:Sa laser) externally. Moreover, absolute intensity and energy calibrations are available. The $H_{2}O$ molecule in vapor phase exhibits a weak absorption spectrum in the visible-UV energy range. Fourier transform spectra are available up to ${\sim} 25000 cm^{-1}$; our experimental setup allows us to probe the UV energy range potentially up to ${\sim} 27000 cm^{-1}$ (i.e. the energy region of the polyad $8\nu, 8\nu + \delta$) with Doppler-limited linewidth and a sensitivity of ${\sim} 4ppb/cm/\sqrt{Hz}$. The modelling of high vibrational energy levels is now available as part of the ab initio investigation of floppy molecules. The new experimental data show poor agreement compared to the available ab initio predictions