INFRARED CAVITY RINGDOWN LASER ABSORPTION SPECTROSCOPY (IR-CRLAS) OF JET-COOLED WATER CLUSTERS

$^{1}$1 J.J. Scherer, J.B. Paul, C.P. Collier, and R.J. Saykally, J. Chem. Phys. 102, 5190 (1995). $^{2}$ J.B. Paul, J.J. Scherer, C.P. Collier, and R.J. Saykally, J. Chem. Phys. 104, 2782 (1996). $^{3}$ J.J. Scherer, D. Voelkel, D.J. Rakestraw, J.B. Paul, C.P. Collier, R.J. Saykally, and A. O'Keefe, Chem. Phys. Lett. 245, 273 (1995).Author Institution: Department of Chemistry, University of California; Department of Chemistry, Sandia National LaboratoriesWe have recently extended the Cavity Ringdown Laser Absorption Spectroscopy $technique^{1,2}$ into the $infrared^{3}$. Studies in the 3.0 $\mu$m region of water clusters in molecular jets have found two vibrationally resolved bands centered at 3356 $\pm$$1 cm^{-1}$ and 3400 $\pm$$3 cm^{-1}$, which have been previously assigned to the water pentamer and tetramer, respectively. Additionally, we observe a broad continuum absorption exhibiting long range structure, attribuitable to an inhomogeneously broadened OH-stretch excitation in large water cluster. This feature exhibits similarities with spectra of large water polymers found in cryogenic matricies, and with the infrared absorption of bulk amorphous ice