2:00 PM - 2:15 PM
▲ [17p-A404-4] Sensitivity Improvements in a Cavity Ring-Down Spectrometer for Radiocarbon Analysis in Biomedical Samples
Keywords:molecular spectroscopy, optical cavity, radiocarbon
An overview and status of our current system for CRDS of 14CO2 in the Mid-IR wavelength range will be given. Our optical cavity is directly coupled to a CHNS elemental analyzer by a computer controlled valve system, allowing quick sample analysis. A liquid nitrogen cold trap can be employed, improving concentration especially for small samples. Attaining high sensitivity requires careful control of environmental variables and contaminants. Thermo-electric cooling of the cavity is applied to suppress interference by absorption of other close-lying molecular transitions. The sensitivity and linearity of our current 14C determination procedure is estimated. Wavelength calibration is performed using a combination of N2O absorption cell and solid silicon etalon, however first Mid-IR frequency comb referenced results were achieved. Oscillations and drifts in the Ring-Down spectrum baseline are a further issue, limiting the sensitivity of the system. While these effects may be partially suppressed by optical isolation, an active pathlength modulation has shown promise as well.