Pressure broadening of the oxygen A-band measured by laser absorption spectroscopy

Spectroscopic concentration measurements of oxygen at high pressures are limited by the effect of pressure broadening and line mixing. These effects strongly depend on the gas mixture in which the oxygen concentration has to be determined as the pressure broadening coefficients of different gases vary over a large range. Line broadening coefficients of the oxygen a-band for a large number of different gases are well known in the literature, but up to now there is, to our best knowledge, no experimental data available which describes the line broadening of oxygen in hydrogen. In respect to a possible application for online-monitoring of oxygen in hydrogen electrolysis we have measured the pressure broadening coefficient of the oxygen P9P9 line in hydrogen and compared with the theoretical m odel. To confirm the result, also measurements of the well known broadening coefficient of oxygen in helium were accomplished. Measurements were obtained using laser absorption spectroscopy with vertical-cavity surface-emitting lasers in a Herriott-Cell with 15 m path length adapted for vacuum pressures.