PERFORMANCE CAPABILITIES OF SMALL GRATING SPECTROMETERS.
NAVAL RESEARCH LAB WASHINGTON D C
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Some of the performance capabilities of grating infrared spectrometers, such as spectral resolving power, wave-number accuracy, analytical sensitivity and accuracy, and qualitative specificity, are demonstrated. Primary emphasis is given to resolving power and wave-number accuracy. The nu sub 3 fundamental of CH3C1 was studied in the gas phase, and the rotational fine structure was analyzed. A spectral resolution of better than 0.25cm and a line position accuracy of about plus or minus 0.04cm were attained. Several rotational constants were determined for CH3C135 and CH3C137, and these agree well with those previously determined from microwave data. The nu sub 3 and nu sub 4 fundamentals of CH4 were examined in the gas phase with various degrees of resolution, using both prism and grating instruments. With the increased resolution of the grating instruments, striking increases in the peak absorptivities of the rotational lines occur, and many previously unresolved lines appear. This increased resolution gives more specific spectra, leading to greater certainty in the identification of unknowns. Substantial improvements in limits of detectability for simple molecules result, and these molecules can be more certainly identified in mixtures because their rotational spectra can be resolved. Author
- Atomic and Molecular Physics and Spectroscopy