Knowledge Bank

We have recently extended the Cavity Ringdown Laser Absorption Spectroscopy $technique1,2$ into the $infrared3$. Studies in the 3.0 $\mu$m region of water clusters in molecular jets have found two vibrationally resolved bands centered at 3356 $\pm$$1cm-1$ and 3400 $\pm$$3cm-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.