The Measurement of Water Vapor Isotope Based on Mid-Infrared Difference Frequency Generation
WANG Zhu-qing1, 2, WANG Huan1, 2, CAO Zhen-song1, YUAN Yi-qian1, ZHANG Wei-jun2, GONG Zhi-ben1, GAO Xiao-ming1, 2*
1. Laboratory of Atmospheric Optics, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China 2. Environmental Spectroscopy Laboratory, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China
Abstract：Stable-isotope ratio analysis of water is an important tool for geology, meteorology, and earth sciences. Measurements of water vapor isotopes are very helpful to explaining stratospheric aridity and related issues in atmospheric sciences. The absorption of water vapor near 2.7 μm is very strong so it is suitable for measuring high sensitivity spectra. Based on difference frequency generation and quasi-phase matching, by mixing an Nd∶YAG laser with Ti∶Sapphire tunable from 750 to 840 nm in a 50 mm long periodically poled lithium niobate (PPLN) crystal, a widely tunable CW laser source was generated for the mid-infrared spectral range from 2.5 to 4 μm. We chose Λ=20 μm for PPLN crystal, the generated laser was around 2.7 μm. This laser is widely tunable and of inherent narrow linewidth based on difference-frequency generation. Using this idler laser and 100 m multi-pass cell, and direct absorption the water vapor isotopes were measured in the laboratory air. The authors measured isotopes ratios and δ17O, δ18O and δD. The values were found to be in excellent agreement with the standard value for three individual lines.
王竹青1, 2，王 欢1, 2，曹振松1，袁怿谦1，张为俊2，龚知本1，高晓明1, 2* . 基于中红外差频激光测量水汽分子同位素丰度[J]. 光谱学与光谱分析, 2009, 29(12): 3271-3274.
WANG Zhu-qing1, 2, WANG Huan1, 2, CAO Zhen-song1, YUAN Yi-qian1, ZHANG Wei-jun2, GONG Zhi-ben1, GAO Xiao-ming1, 2*. The Measurement of Water Vapor Isotope Based on Mid-Infrared Difference Frequency Generation. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2009, 29(12): 3271-3274.
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