PNNL

Abstract

An optical flow-cell for high pressures and temperatures is described. The use of a novel window design allows for a precise, fixed optical path length that can bee varied by use of spacers from a few micrometers to several millimeters. The cell pathlength is not affected by changes in pressure or temperature. The novel window design may be applicable to other high-pressure spectroscopic cells. The flow-cell design has a minimal sample dead volume, which is important for kinetic studies. The design eliminates the needs for frazing or a soft-sealing material for the optical windoes, thereby minimzing the number of materials in contact with the sample. Using only diamond and platinum or platinum alloys as the corrosin resistant materials, the design is optimized for the study of aqeous solutions at high temperatures. Infrared spectra of an aqueous sodium tungstate solution up to 400 degrees C and 380 bar pressure are presented. Time-resolved IR data are also presented for the UV-photolysis reaction of beta-naphthoyl azide (BNA) in supercritical carbon dioxide.