MEASUREMENT OF (CO2)-C-12(CO2)-C-13 RATIOS FOR MEDICAL DIAGNOSTICS WITH 1.6-MU-M DISTRIBUTED-FEEDBACK SEMICONDUCTOR DIODE-LASERS

We have observed some of the absorption lines from the molecules (CO2) -C-12 and (CO2)-C-13 in the 1.6-mu m spectral region with the use of s pecially fabricated single-mode InGaAsP distributed-feedback semicondu ctor diode lasers. Using a 23.6-m-long multipass absorption cell in co mbination with radio-frequency modulation and detection techniques, we measured the (CO2)-C-12:(CO2)-C-13 isotopic ratio of two specific lin es at 6253.73 and 6253.90 cm(-1) with sufficient precision for diagnos tic medical tests that analyze CO2 on human breath.