IR and Raman spectroscopic measurements of water at high temperatures and pressures

Abstract

High temperature pressure cell for micro IR and Raman spectroscopy have been developed to investigate molecular structure of water under sub and supercritical conditions. The maximum temperature and pressure of the cell were 400 C and 50 MPa, and artificial yellow diamond was installed as a transparent window of the cell. In case of micro IR spectroscopic measurement, incident beam was illuminated to the high temperature pressure cell using the Cassegrainian mirror, and reflected light was analyzed by FTIR system. In case of micro Raman spectroscopic measurement, an incident laser beam (Nd:YAG laser: 532 nm) was irradiated into the cell through standard optical lens. As a result of infrared spectroscopic measurements of water, the broad peak around 3360 cm 1 of infrared spectra, attributed to OH stretching vibration mode of water molecular, was observed at room temperature and pressure. The peak position shifted to higher wavenumber with increasing temperature and shifted to lower wavenumber with increasing pressure. Continuous shift of the OH stretching vibration mode of water molecule was detected by using newly designed high temperature pressure cell. The peak position and behavior of peak shift of interfacial water were affected by substrate. In case of interfacial water on artificial quartz, the peak position shifted to higher wavenumber with increasing temperature, however no obvious change was observed with as a function of pressure.It was possible to measure IR and Raman spectra under supercritical condition by using high temperature pressure cell, and characteristics of molecular structure of interfacial water revealed by IR spectra was changed by environmental conditions such as temperature, pressure and substrate.

First Direct Observation of Elementary Steps on the Surfaces of Glucose Isomerase Crystals under High Pressure

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Experimental estimation of Molecular structure of the Water-Rock interface inferred from in situ IR-Raman Spectroscopy up to 40 °C, 50 MPa

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