LASER DIODE SPECTROMETER FOR ANALYZING THE RATIO OF ISOTOPIC SPECIES IN A SUBSTANCE

摘要

A diode laser spectrometer (10) includes a sample chamber (68) for holding a sample gas, e.g., human breath, having first and second isotopic species in an unknown concentration ratio and a reference chamber (70) for holding a reference gas having the first and second isotopic species in a known concentration ratio. Laser light is directed (32, 34) through both chambers at wavelengths corresponding to absorption wavelength of the isotopic species, and the light is detected (56, 58) and sample and reference signals generated. The signals are processed by a computer (12) to determine the concentration ratio of the first isotopic species to the second isotopic species in the sample gas. The diode laser (24) is cooled by a thermoelectric cooler (36) or a cryocooler (36) operating as a reverse Sterling engine.