For more details, please check our publications. Absorption lines in the 2 band of water vapor at 6.3 micrometers have been fully resolved by using a tunable semiconductor laser. We gratefully acknowledge finanical support by the BMBF within contract 13N7157. These experiments have been performed with our TEC100 Littrow Laser System, as well as with our TEC500 Littman Laser System. The 2f absorption spectra recorded with a Lock-In amplifier are shown in the figure. In another experiment, wavelength modulation spectroscopy was accomplished by mixing a low and a high tuning frequency. In this figure, the detected optical density at the absorption maximum at a line at 1367.86nm is plotted versus the absorption coefficient calculated according to the Hitran database. Some of these strong line at 1388nm are shown in the figure, detected with a simple water vapor absorption experiment. In the Hitran database, many transitions can be found, and there are several strong absorption lines the 1390nm regime, for example. However, in some 'applications' the amount of water vapor needs to be exactly measured. The results were compared with the Fourier transform spectrometer which performed the measurements simultaneously, the variation trends of the two methods were consistent. Without water, there would be no life possible on this planet. The absorption spectrum of atmospheric water vapor in Hefei was measured, and the water vapor concentration was inverted by the OEM. Such a measurement absorbance profile covered two absorption lines, and was modeled to a double Voigt profiles to yields the integrated absorbance areas for each transition, as also showed in the Figure 6b. Strong water vapor absorption bands occur at wavelengths around 2500, 19 nanometers (nm), with weaker absorption around 1200 and 970 nm, and three additional sets of water-vapor absorption lines near 930, 820, and 730 nm, all in the infrared spectrum. Water is the most important molecule on earth. The absorption spectrum of water vapor was calculated as v ln (I 0 / I t), shown in Figure 6b.
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