Development of a Stable Carbon Isotopes Analysis Instrument Based on Tunable Diode Laser Absorption Spectroscopy

Abstract

Abstract A compact laser spectrometry instrument was developed for high precision measurements of isotope ratio of CO2 by tunable diode laser absorption spectroscopy in the mid-infrared at 2.7 μm. The experimental spectrum of carbon isotopologues in the gas phase near 3641 cm−1 is very suitable for real-time analysis of these isotopologues. Simultaneous measurements of the mixing ratio and the corresponding δ13C values of CO2 in the atmosphere were performed. The achieved standard deviation (1σ) of δ13C was 1.8‰. The Allan analysis of the time series of the mixing ratio of CO2 shows a measurement precision of 0.2‰ for δ13C with an optimum integration time of about 130 s. The spectrometer is capable of real-time measurements of stable carbon isotope ratios of CO2 under ambient conditions.