On the Resolving Power of a Prism Spectrometer for the Infrared

The resolving power of a spectrometer in the infrared is limited by the rate at which energy passes through the exit slit of the spectrometer. Calculation of the energy available for activating a thermocouple, under condition that the exit slit embrace the same frequency range $\Delta \nu$ of spectrum at all times, gives information on the attainable resolving power at various wave-lengths and with various prisms. The best dispersing angle for a sylvine prism to be used from 8 to 22μ is from 70° to 75°. A lamellar prism construction is described.