Sensitive measurements of stable carbon isotopes of CO₂ with wavelength modulation spectroscopy near 2 渭m

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• 作者：K. Tanaka (12)
  K. Tonokura (12) tonokura@k.u-tokyo.ac.jp
• 刊名：Applied Physics B ; Lasers and Optics
• 出版时间：November 2011
• 出版年：2011
• 期刊代码：10_0946-2171
• 类别：bus
• 卷：105
• 期：2
• 页码：463-469
• 数据来源：sp

摘要

We performed highly sensitive measurements of stable carbon isotopes of CO₂ using wavelength modulation spectroscopy with a distributed feedback laser diode in the 2-μm wavelength range. Ro-vibrational transitions, which belong to the different combination bands, were selected to measure the 13CO₂/12CO₂ carbon isotope ratio. The δ 13C value was determined through the signals obtained in a Herriott-type multipass cell with an optical path length of 29.9 m. The limit of detection for CO₂ using our measurement system was 16卤1 parts per billion by volume at the strongest absorption peak that is assigned to the 2ν ₁+ν ₃ R(16) line within the laser emitting frequency region. The 10-h long term precision was a δ 13C standard deviation of 0.24‰ (1σ) with the best suited line pairs of 12CO₂ and 13CO₂ and with careful temperature and pressure control in the cell. The 3-min response and high precision of this measurement allows for precise continuous measurements of stable carbon isotopes in ambient CO₂.