Detection of Stable Isotopes of CO2 using Quantum Cascade Laser based Absorption Spectroscopy

A spectroscopic approach to measure 13C and 18O isotopic ratios in carbon dioxide (CO2) gas using a quantum cascade laser (QCL) is presented. The measurement was performed near 2310 cm-1, where three absorption lines of CO2 including 12C16O2, 13C16O2 and 16O12C18O isotopes are located. The simultaneous detection of three spectral lines permits the determination of simple concentration ratios (R13 and R18) in atmospheric CO2. With an averaging time of about 20 s both R13 and R18 reached a precision (1s) of 0.08 0 and 0.01 0, respectively.