Laser spectroscopic gas concentration measurements in situations with unknown optical path length enabled by absorption line shape analysis

摘要

The concentrations of molecular oxygen and nitrogen in a gas mixture were determined by their impact on the shape of a water vapor line in the near infrared region using diode laser absorption spectroscopy. The shape of the water vapor line depends on the composition of other gases in the mixture and can therefore be used to deduce the concentration of partner molecules, e.g., oxygen, in the buffer. The method enables gas concentration measurements in situations when the path length is unknown, measurements of many gases simultaneously, and measurements of gases lacking suitable absorption lines.