Estimation of line width by self-absorption measurement using Fourier transform infrared spectrometry.

A simple method of estimating the width of a narrow spectral line with a low-resolution optical system has been proposed. The method consists of the measurement of an emission spectrum of a gaseous sample, and measurement of the amount of its attenuation caused by placing an absorption gas cell filled with the same chemical species as that emitted. If the line width of either emitting or absorption gas is known, the line width of the other can be obtained by calculation. Two sets of experiments were conducted on carbon monoxide (CO); (1) measurement of pressure broadening in the line widths of the absorption lines of CO by the use of narrow CO emission lines, (2) measurement of the line widths in the emission lines of CO by the use of a set of absorption lines of CO, whose widths are known. As a result, the translational temperature of the emission system was determined.