Robert F. Stamm

The Vibrational Spectrum and Thermodynamic Functions of Acrylonitrile

The infra‐red spectra of gaseous and liquid acrylonitrile have been studied from 2.5 μ to 25 μ with a spectrometer using LiF, CaF2, NaCl, and KBr prisms. The Raman spectrum of the liquid has been obtained, including intensity and polarization data. A normal coordinate calculation of the non‐planar frequencies has been made, using force constants from related molecules. This information permits a complete assignment of the fifteen fundamental frequencies and a calculation of the thermodynamic quantities for the molecule.

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.

Photoelectric Raman Spectrometer with Automatic Range Changing. I. Conversion of Photographic Instrument

The emphasis in this paper is on the circuitry aspect of the problem of converting a photographic Raman instrument into a photoelectric Raman spectrometer. The reconstructed instrument was tested by using a scanning-slit mechanism in the focal plane of the camera lens of a grating spectrograph. A photomultiplier tube served as the detector and was operated in a vacuum housing at the temperature of liquid nitrogen. A tetrode electrometer tube in a low gain circuit yielded a nearly linear output which was graphically recorded. A spiral mercury arc provided sufficient illumination to enable reproduction of intensity measurements to within ±1 percent at a scanning rate of about 3 cm−1 per second. An automatic range changing device extends the range of intensities which can be recorded on the normal ten-inch chart.