Determination of Low Concentration HD through Laser Thermal Lensing Spectroscopy

1999 Fiscal Year Final Research Report Summary

• Project/Area Number: 10480116
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Nuclear engineering
• Research Institution: Nagoya University
• Principal Investigator: ENOKIDA Youichi Nagoya University, School of Engineering, Associate Professor, 工学研究科, 助教授 (40168795)
• Co-Investigator(Kenkyū-buntansha): KOBAYASHI Noboru Nagoya University, School of Engineering, Research Associate, 工学研究科, 助手 (70293652) ; YAMAMOTO Ichiro Nagoya University, School of Engineering, Professor, 工学研究科, 教授 (50023320)
• Project Period (FY): 1998 – 1999
• Keywords: Isotope Separation / Hydrogen isotopes / Laser / Thermal lensing / Spectroscopy / Infrared / Low concentration analysis / HD

Research Abstract

Laser-induced thermal lensing spectroscopy was studied to analyze hydrogen gas which contained natural abundance of HD, 300ppm. An infrared laser system of 1.382 μm InGaAs P type was used to excite HD molecule with a precise temperature control and frequency modulation of 1.4 to 110 kHz. At first, infrared spectrum of HD was measured with a single-path cell which contained HD gas of 100 to 800 torr and 0.8 mm long. The R(1) branch of the 2-0 band was observed with a half width of 0.02 cmィイD1-1ィエD1 at 7241.82 cmィイD1-1ィエD1, which was the same wavelength observed by Herzberg in 1950. The detection limit of HD with a normal adsorption spectroscopy was 20 torr, which was equipment to a concentration of 100 times higher than that of the natural abundance of HD. We applied a multi-path cell of 32 m in the effective path length to detect HD at the low pressure of less than 20 torr, but background noise brought about by the multi-reflection was too high detect HD absorption. In the thermal lensing spectroscopy, a reference cell which was evacuated less than 0.001 torr and 0.8 m long was placed in a parallel geometry of the sample cell contained the HD gas of 0.2 to 2 torr. Each laser beam was passed through a pinhole of 0.1 mm in diameter and detected. A difference signal was detected for a sample of 0.2 torr HD with 100kHz modulation, and it shows that we can determine HD molecule of the natural abundance with thermal lensing spectroscopy.