S. Silverman

Precise Measurements in the Infrared Spectrum of Carbon Monoxide

New measurements have been made in the CO infrared spectrum in both emission and absorption, using a 15,000‐line/inch grating spectrograph and a 7200‐line/inch vacuum grating spectrograph. High precision in wavelength determinations was obtained by superimposing on the spectra emission lines in higher order of Hg, Kr, and A discharges. The measurements are believed accurate to ±0.02 cm−1. The observed lines in absorption are those of the 2–0 and 3–0 bands of C12O16, between R 30—P 29 and R 9—P 16, respectively; 27 lines of C13O16 and 10 lines of C12O18 have also been measured. In emission from oxy‐acetylene and CO–O2 flames, over 300 lines in the 2–0, 3–1, 4–2, and 5–3 bands have been identified between 4360 and 4000 cm−1. The emission bands form heads in the R branch near J=50, and the 2–0 band shows resolved lines out to J=46 in both P and R branches.The new measurements are in good agreement with earlier results at low quantum numbers, but show discrepancies at high numbers which result in slightly dif...

The Determination of Flame Temperatures by Infra-Red Radiation

The determination of flame temperatures by infra-red radiation has been reinvestigated based on the experiments of Schmidt, Henning, and Tingwaldt. Criteria for such a brightness thermometer are described, and means for minimizing some of the errors are discussed. It is concluded that (a) infrared emission for the CO2 band at 4.4 microns can be used at least for non-luminous flames which contain CO2 as one of the products of combustion, (b) temperatures are obtained that are consistent to within less than 5 percent, and (c) observed temperatures tend to be lower than theoretical temperatures.

A Rapid Scanning Spectrometer for Oscillographic Presentation in the Near Infra-Red*

A rapid scanning spectrometer for oscillographic presentation has been built for use in the “photo-conductive” infra-red region. It is designed to present spectra from 0.36μ to better than 5μ using a PbTe cell. The CO2 doublet at 4.2μ is resolved with a scanning rate of 120 cycles per second and a scanned interval of better than 1.5μ with fluorite optics. A wave-length calibrating device has been incorporated into the instrument; this presents a fiduciary scale, synchronized with the spectrum, on the second beam of the twin-beam cathode-ray oscillograph. Adequate solutions have been found for the problems of synchronizing oscilloscope sweep and scanning drive, and for the problems of amplifier design for the sensitive cells.

The Infra-Red Emission Spectra of the Oxy-Hydrogen and Oxy-Deuterium Flames*

The infra-red emission spectra of the oxy-hydrogen and oxy-deuterium flames and of hot water vapor have been studied in the LiF, NaCl, and KBr regions. The principal features of the spectrum may be accounted for by emission of H2O molecules; no unequivocal evidence for radiation from OH radicals was found with the resolving power available.

Spectral and pressure observations of explosion phenomena.

A Perkin-Elmer Model 83 Monochromator covering a spectral range from the ultraviolet to 5.5μ is used for determining the light intensity as a function of time of an explosion in a bomb. [ Bullock Hornbeck Silverman , J. Chem. Phys.18, 1114 ( 1950)]. The radiation entering the spectrometer is chopped to allow ac amplification of the detector output with provision to allow transmission as well as emission measurements. A frequency modulated pressure gauge is used to determine the pressure change in the bomb. Time resolution of the order of magnitude of 10−3 sec may be obtained for both spectral and pressure observations. Results for typical carbon monoxide-oxygen explosions are shown. These preliminary results seem to indicate that there is equilibrium for approximately 0.02 sec after the flame front reaches the vessel wall.

A Cinema-Spectrograph for Photographing Rapid Spectral Sequences*,**

A simple spectrograph designed around a 16-mm movie camera is described. The spectrograph was built for the purpose of obtaining spectrograms from light sources showing transient phenomena, in particular such light sources as the new types of rocket and jet combustion engines. The study of the light emitted from an acetylene-oxygen flame as a function of time illustrates its usefulness.

The Decoloration of Natural Fluorite Crystals

The simple heat treatment for decoloring fluorite crystals of various hues is described. The improvement in transmittance is shown by means of spectrophotometer curves.