Edgar A. Rinehart

Linewidths of the Microwave Inversion Spectrum of Ammonia

The linewidths of some 25 inversion spectral lines of ammonia in the frequency region of 18–29 kMc/sec have been measured. Corrections due to various effects such as source modulation, cell‐length broadening, and Doppler shift were applied to the experimental data to evaluate the linewidth parameters. Self‐broadening and foreign‐gas broadening by some 15 different gases have been studied. In the case of self‐broadening of the series of lines with J=K for which the effect of rotational resonance is negligible, the width parameters determined experimentally agree well with those calculated by Andersons theory from (2, 2) to (5, 5), but appreciable deviations are found at higher J. For the lines with J≠K, the discrepancy becomes larger and increases with increasing difference between J and K. The quantum number dependence of the foreign‐gas broadening by methyl chloride and by carbon dioxide has been investigated in detail. For methyl chloride broadening the theoretical and measured widths agree with each o...

Microwave Spectrograph for Linewidth Measurements

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Sensitive Triple Modulation Method for Measuring Widths of Microwave Spectral Lines

Supported jointly by the National Science Foundation and the Office of Naval Research.

Microwave Power Leveler for K Band

A microwave spectrograph designed for measurements of linewidth is described. The width spectrograph consists of the same general major components as a spectrograph for frequency measurements, but differs considerably in the requirements of the components and the assembly thereof since many factors which have virtually no effect on the frequency of a spectral line could influence the width significantly. Methods are given to generate a stable and pure frequency‐modulated microwave signal which has a constant power output over a frequency range of 10 Mc. Great precaution must be made in assembling the waveguide components to reduce reflection in the absorption cell. For each crystal detector one must select the optimum load resistance (generally ranging from 3 kΩ to 1 MΩ) to insure square‐law response since deviation from this behavior may introduce an error as large as 4%. A discussion of the general procedure of linewidth measurements which includes modulation and length corrections is given.

System for Processing and Recording Excitation Function Data

A method has been devised for the measurement of microwave spectral line widths with high sensitivity. This method consists of a combined source modulation of the microwave power at 2.3 kc and Stark modulation at 100 kc in addition to the slow sawtooth sweep voltage. The use of two rf modulations eliminates the base line which arises from the variation of the klystron power with frequency. The base remains flat for a source modulation amplitude as high as 1 v. The sensitivity is greatly improved over the previous method in which only source modulation is used. It is suggested that the technique of triple modulation may also be used to resolve closely spaced lines.A method has been devised for the measurement of microwave spectral line widths with high sensitivity. This method consists of a combined source modulation of the microwave power at 2.3 kc and Stark modulation at 100 kc in addition to the slow sawtooth sweep voltage. The use of two rf modulations eliminates the base line which arises from the variation of the klystron power with frequency. The base remains flat for a source modulation amplitude as high as 1 v. The sensitivity is greatly improved over the previous method in which only source modulation is used. It is suggested that the technique of triple modulation may also be used to resolve closely spaced lines.

Determination of the A2 torsional frequency in trimethylamine by computer-aided microwave relative intensity measurements☆

A device has been developed for regulating milliwatts of microwave power in the 24‐kMc region. The power leveler has been shown to operate over the electronic sweep range of a K‐band reflex klystron, and to regulate power to within ±0.5%.

Experimental evidence of laser-induced separations in bulk gas mixtures (A)

A system which automatically processes optical excitation data is described. This system is capable of producing data faster and of better quality than the old method. The apparent cross section for excitation by electron impact of a particular state is proportional to the light intensity of a radiative transition from this level divided by the product of the electron beam current times pressure. The light intensity is measured from the output current of a photomultiplier tube. When the pressure in the collision chamber is maintained constant, the apparent cross section is proportional to the ratio of photomultiplier current to electron beam current. This ratio is continuously computed by an analog divider while the electron accelerating voltage power supply is slowly swept through its range by a motor and gear reduction system so as to give a visual display of the excitation function on an oscilloscope. Permanent records of the function are made by photographing the trace. Absolute values of the excitati...