A Laboratory Study of Absorbing Capacity of Water Vapor at the Wavelengths from 6500 TO 10500 {\AA}

TL;DR

This study provides empirical spectral data and functions for water vapor absorption in the 6500-10500 Å range, aiding correction of astronomical observations for atmospheric water vapor effects.

Contribution

It introduces empirical functions and parameters for water vapor absorption correction in the specified spectral range, based on laboratory measurements.

Findings

Spectral absorption data for water vapor at 6500-10500 Å.

Empirical functions approximate absorption with about 1% accuracy.

Parameters enable correction of stellar spectra for atmospheric water vapor.

Abstract

We obtained laboratory spectra of absorption by water vapor at the wavelengths 6500-10500 {\AA} with the multipass cell. The water vapor content along the line of view varied from 0.1 to 3.0 cm of precipitated water, the pressure from 0.1 to 1.0 atm. The spectra were taken with the width of the exit slit of the spectrophotometer 25, 50, 100, and 150 {\AA}. To match these spectra, we selected empirical functions, which approximate the observed absorption within the indicated interval of water vapor content and pressure with the accuracy about 1%. For the water vapor band at the wavelengths regions 7200, 8200, and 9300 {\AA}, with the step 25 {\AA}, we determined the parameters necessary for the calculation of empirical transmission functions. The presented data make it possible to select the parameters for taking into account the radiation attenuation in the spectral region of telluric water vapor under the conditions of real astronomical observations for a specific place and spectrophotometer. The suggested set of empirical parameters may provide correction of observed stellar spectra for the extinction in the atmosphere with the accuracy 0.m01-0.m02.