Saturation effect for H(2)O absorption lines at ruby laser wavelengths

Area of Science:

• Atmospheric optics
• Laser spectroscopy
• Molecular absorption

Background:

• Atmospheric water vapor significantly influences radiative transfer.
• Understanding water vapor absorption is crucial for climate modeling and remote sensing.
• Laser-based methods offer high sensitivity for probing molecular absorption spectra.

Purpose of the Study:

• To experimentally determine the dependence of atmospheric water vapor absorption on ruby laser radiation intensity.
• To measure the spectral absorption line contours of H2O at specific wavelengths.
• To investigate the pressure dependence of the saturation parameter for water vapor absorption.

Main Methods:

• Utilized an optoacoustic laser spectrometer with high sensitivity (10^-9 cm^-1 J^-1).
• Measured H2O absorption line contours at 694.215 nm, 694.238 nm, and 694.38 nm.
• Varied laser radiation intensity (5-100 MW/cm^2) and pressure (250-750 Torr).

Main Results:

• Observed a decrease in absorption at line maximum with increasing laser intensity, indicating spectral saturation.
• Calculated saturation parameters for three H2O lines: 210±23 MW/cm^2, 140±15 MW/cm^2, and 180±20 MW/cm^2.
• Found satisfactory agreement between experimental and calculated absorption parameters; investigated pressure dependence for the 694.38 nm line.

Conclusions:

• Demonstrated the intensity-dependent nature of atmospheric water vapor absorption.
• Provided quantitative measurements of spectral saturation parameters for specific H2O absorption lines.
• The findings contribute to a better understanding of laser-water vapor interactions under varying atmospheric conditions.