LASER-BASED ANALYSIS OF CARBON-ISOTOPE RATIOS

A laser technique for analysis of carbon-13:carbon-12 ratios with the specificity of laser resonance spectroscopy and the sensitivity and ac curacy typical of isotope ratio mass spectrometers is reported. The te chnique is based on laser optogalvanic effect spectroscopy, in which a n electrical (galvanic) signal is detected in response to the optical stimulation of a resonance transition in a gas discharge species. Carb on dioxide molecular gas lasers are used, with the probed transitions being identical to the lasing transitions. Measurements for carbon dio xide samples with 100-second averaging times yield isotopic ratios wit h a precision of better than 10 parts per million.