Isotope analysis of water by means of near-infrared dual-wavelength diode laser spectroscopy

A novel diode laser spectrometer was developed using dual-wavelength multiplexing, ensuring ideal conditions for high-precision and simultaneous measurements of the H-2/H-1, O-17/O-16, and O-18/O-16 isotope ratios in water. A 1.4-mum diode laser probed a (HOH)-O-16/(HOH)-H-2 line pair near 7198 cm(-1), while a similar laser observed (HOH)-O-16, (HOH)-O-17, and (HOH)-O-18 rovibrational lines around 7183 cm(-1), or a (HOH)-O-16/(HOH)-O-18 line pair near 7200 cm(-1). The 1-sigma standard deviation is 0.2parts per thousand for O-18/O-16, and 0.5parts per thousand for the H-2/H-1 and O-17/O-16 isotope ratios. Preliminary experiments with repeated injections of a natural abundance sample point to an accuracy of about 1parts per thousand for all three isotope ratios in natural samples. (C) 2003 Optical Society of America.