A VACUUM GRATING SPECTROGRAPH FOR THE $INFRARED^{*}$

$^{*}$Supported in part by the Office of Ordnance Research, U. S. Army. $^{\dagger}$Now at Bell Telephone Laboratories, Murray Hill, New Jersey.Author Institution: The University of Tennessee“A vacuum-grating spectrograph has been designed and constructed using a modified Pfund type optical system. Incorporated in the instrument is a Fabry-Perot calibrating system which makes it possible to obtain measurements with an absolute accuracy of about $\pm 0.01$ $cm^{-1}$. The instrument is housed in a large vacuum tank and is operated by means of synchro control systems. There are at present four gratings available for use in the spectrograph, which span the region from 400 to $8500 cm^{-1}$. The spectrograph has been tested and has produced data with a resolution of $0.1 cm^{-1}$ in the 2.7 $\mu$ region using a Reeder thermocouple. Slides showing the details of the instrument will be shown.