Development of a compact quantum cascade laser spectrometer for field measurements of CO_2 isotopes

摘要

We report the development of a field-deployable, pulsed quantum cascade laser spectrometer. The instrument is designed to measure the ~(13)C/~(12)C isotopic ratio in the CO_2 released from volcanic vents. Specific ~(12)CO_2 and ~(13)CO_2 absorption lines were selected around 4.3 μm, where the P-branch of ~(12)CO_2 overlaps the R-branch of ~(13)CO_2 of the 00~01-00~00 vibrational transition. This particular selection makes the instrument insensitive to temperature variations. A dual-channel cell balances the two absorption signals. We provide details of the instrument design and a preliminary demonstration of its performance based on laboratory measurements of ~(16)O~(12)C~(16)O and ~(16)O~(12)C~(18)O.