Measurement of broadening coefficients of water vapor molecules near 1.517 μm with continuous-wave cavity ring down spectroscopy

In order to explore the relation between N2-broadening and air-broadening coefficients of water vapor molecules in near-infrared region, a high-sensitive continuous-wave cavity ring down spectroscopy, which used a glass-ceramic as the cavity and a distributed feedback diode laser as the light source, was applied to measure the spectral lines of water vapor molecules(near 1 517 μm in the spectral region of 6 586.5~6 596.5 cm-1), and the noise (RMS) equivalent absorption sensitivity of about 3.2×10-9 cm-1 was achieved. According to those measured broadening coefficients of water vapor molecules in air and in N2, their ratio is obtained as 0.896 9±0.068 7(within 3 times the standard deviation), which is in agreement with the resul