Photoelectric Raman Spectrometer with Automatic Range Changing II Conversion of Perkin-Elmer Infrared Instrument to Grating Type

A Perkin-Elmer model 12 infrared spectrometer has been converted to a plane grating spectrometer for recording Raman spectra photoelectrically. The light source is a Toronto-type, helical mercury arc which illuminates the sample (either 4.5 cc or 9 cc) contained in a vertical, cylindrical tube. The sample tubes are provided with back-surface, concave mirrors (held in the rear of the tubes and integral with the stoppers) thereby doubling the intensity. The difficulties experienced with grating ghosts are discussed along with the requirements for the grating. The fine structure of the CCl4 459 cm−1 and C6H6 992-cm−1 lines can be resolved using a 9-cc sample. With reference to 992 of benzene, a signal-to noise ratio of 120:0.15 can be achieved with a time constant of 12sec and permits spectra to be obtained at a rate of 0.83 cm−1 per sec with intensity ratios correct to within ±1 percent.