Microplasma emission spectroscopy of stable isotope ratios in carbon dioxide

This study investigates the prospects of using emissions from the discharge of a stripline split-ring resonator microplasma source to measure the 13 C/ 12 C isotope ratio in CO 2 . The plasma source was used in a measurement scheme called microplasma emission spectroscopy, in which the visible emission spectrum of the CO 2 discharge was investigated using a CCD spectrometer. The study revealed that the major isotope dependencies of the spectrum originated from the Ångström system (B1Σ+→A1Π) of CO molecules that had been converted from CO 2 in the discharge. Although at least four of the bands of the Ångström system showed clear isotopic dependences, the (0-3) band at 561 nm was concluded to show the most prospects for spectrometric applications because of a combination of wide isotopic shift and low background. A theoretical model of this band was constructed and used in a partial least squares fitting algorithm, to quantify the abundance of 12 C and 13 C in the sample. This signal processing method was shown to be robust and linear over the whole dynamic range of 13 C/ 12 C ratios (1-100%) but required a ten-fold improvement in precision and accuracy at naturally occurring 13 C levels (1.07-1.12%) to be useful in most scientific applications. However, several promising ways of achieving such an improvement have been presented, and the results demonstrate the potential of creating a simple, cost-effective, and highly miniaturized system for isotope ratio measurements, which could offer great advantages to scientists in many different fields, from environmental science to planetary exploration.