[17p-A404-1~14] 3.16 Optics and Photonics English Session

▲ [17p-A404-4] Sensitivity Improvements in a Cavity Ring-Down Spectrometer for Radiocarbon Analysis in Biomedical Samples

〇(PC)Volker Thomas Sonnenschein¹, Ryohei Terabayashi¹, Hideki Tomita¹, Noriyoshi Hayashi¹, Shusuke Kato¹, Lei Jin¹, Masahito Yamanaka¹, Norihiko Nishizawa¹, Atsushi Sato², Kenji Yoshida², Kohei Nozawa², Tetsuo Iguchi¹ (1.Nagoya Univ., 2.Sekisui Med. Tokai)

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.