Knowledge Bank

Molecular spectra have been recorded at $0.0025cm-1$ resolution using the 1-meter FTS of the National Solar Observatory located at Kitt Peak. This was accomplished by converting the normal double-input, double-output optical arrangement which single-passes the cat's-eyes to a single-input, single-output arrangement which double-passes the cat's-eyes. The conversion is done in a simple manner by inserting two flat mirrors and a compensator into the infrared beams and by placing the detector at the second input port of the FTS. The HeNe reference interferometer is not affected by the conversion, and the alignment for single-pass operation is not altered, so that conversion to and from the double-pass arrangement requires minimum modification to the instrument. Spectra of several gases have been recorded using the increased resolution of the FTS, and examples of these will be shown.