Knowledge Bank

The fundamental mode, $\nu 3$, of $CO2$ at 4.3 $\mu$ has been re-examined under high dispersion in a vacuum grating spectrometer equipped with a Reeder thermocouple and a 7500 lines-per-inch Bausch and Lomb grating. The spectrometer tank was pumped down to a pressure of about 40 $\mu$ and $CO2$ was admitted to a pressure of 1 mm. The total optical path in the spectrometer is about 8.5 meters. At this pressure and path length the $C12O2$ lines absorb about 40% at the peak. Silt openings represent about $0.1cm-1$. Lines of $C12O216,C13O216$, and $C12O16O18$ are easily seen and their frequencies are being determined in a vacuum by means of a comparison spectrum of neon lines from a hollow cathode discharge in higher orders of the grating. The molecular constants obtainable from his band will be redetermined.