Intracavity Optogalvanic Spectroscopy System for Radiocarbon Analysis

An improved intracavity optogalvanic spectroscopy (ICOGS) system (Daniel E.Murnick, Ozgur Dogru and Erhan Ilkmen, \textit{Analytical Chemistry}, \textbf{80}, 4820-4824 (2008)) for $^{\mathrm{14}}$C analysis is under development. A new discharge excitation and monitoring circuit with extremely stable voltage and current characteristics provides long term system stability and reproducibility. To ensure quality data, many dependent parameters are optimized including: gas pressure, gas flow, and a CO$_{\mathrm{2}}$ sample injection protocol. Control measurements are carried out using CO$_{\mathrm{2}}$ free air and 1{\%} CO$_{\mathrm{2}}$ in air standards. The ICOGS signal consists of the $^{\mathrm{14}}$CO$_{\mathrm{2}}$ contribution plus backgrounds from both the standard air and the dominant stable carbon isotopes. We have developed a mathematical vector deconvolution model in order to quantify precisely the $^{\mathrm{14}}$CO$_{\mathrm{2}}$ component of the ICOGS signal. ~We determine each component via vector decomposition to calculate the laser induced change in discharge impedance due to the presence of $^{\mathrm{14}}$CO$_{\mathrm{2}}$. Our objective is to develop a calibration curve in order to obtain accurate measurements for small unknown samples of CO$_{\mathrm{2}}$. Such measurements will be useful in many fields, such as radioactive tracing in biology and medicine and monitoring the concentration of radiocarbon in the atmosphere. ~