Abstract

In continuation of work previously reported [ J. Opt. Soc. Am. 44, 346 ( 1954)], a 150-line-per-mm Bausch and Lomb grating has been installed in a Perkin-Elmer Model 99 double-pass monochromator. With a lead-telluride cell as detector and a selenium-coated germanium filter to remove higher orders, high-resolution spectra have been measured over the range 3–5 microns. Rotational fine structure spacings of 0.3 cm⁻¹ or less have been resolved, and wave numbers measured with a precision of 0.1 cm⁻¹ or better. Calibration was done by means of higher orders of atomic lines, chiefly neon and argon. Precision of the measurements was sufficient to demonstrate that published data on methane and carbon dioxide in this region contain random errors. As an example of the usefulness of the instrumentation, it may be mentioned that rotational fine structure in cyclopropane and cyclopropane-d₆ has been easily resolved and the C-C distance in the molecule determined as 1.524±0.014 A.

© 1955 Optical Society of America

Infrared Spectroscopy from 5 to 200 Microns with a Small Grating Spectrometer*

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Photoelectric Raman Spectrometer

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Quantitative Method for Measuring the Resolution of a Large Grating*

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Stigmatic Plane Grating Spectrograph with Order Sorter

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