THE STRENGTHS, WIDTHS, AND SHAPES OF INFRARED LINES: I. GENERAL CONSIDERATIONS

Abstract

A discussion is given of methods by which the strengths, widths, and shapes of spectral lines may be derived from measurements obtained with spectrometers whose resolving power is sufficient to separate individual spectral lines but is insufficient to portray accurately the true line contour. The Lorentz shape for collision broadened lines is taken as a first approximation to the true line shape for most of the discussion. Numerous corrections that should be taken into account in interpreting experimental data are included. These arise from instrumental effects, overlapping of the individual lines, and deviations from the Lorentz shape. The three types of measurements discussed in some detail are the measurements of the "equivalent width," of the apparent breadth of a line at high optical density, and of the apparent extinction of a line or group of lines at the troughs between lines and in the wings. It is shown how these various types of measurements can be combined to yield the line strength, width, and shape.