Microwave Spectrograph for Linewidth Measurements

Abstract

Articles you may be interested inHigh precision metrology based microwave effective linewidth measurement technique Rev.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 kn to 1 Mn) to in-.sure 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. AbsorptionCell

Lineshape Measurements of Rotational Line in Millimeter-Wave Region by Second Harmonic Detection

“…5) [7], the wall collisions effects Δvwall of the order of 0.5 kHz, saturation phenomena Δvsat = 0.1 MHz [9], harmonic distortion in the modulation 1.56%, nonlinearity of the diode 0.4%, nonlinearity of the frequency scale 3.4%, nonlinearity of the amplification 0.06% and the Doppler broadening ΔvD (Fig. 6) [6] are obtained from the extrapolated linewidth Δv1.…”

Pressure broadening ofJ= 1–0 rotational line of the CHF3molecule in an electric field

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The Collision Broadening of Spectral Lines

“…This has formed the basis for much of the interpretation of experimental measurements of the widths of spectral lines in the microwave region; selected references will be found in the paper by Rinehart, Legan, and Lin (1965). Either the width between the half-power points, or, in the case of the work of Rinehart, Legan, and Lin, the width between the points of steepest slope, is measured for various gas pressures and the mean intervals between collisions are calculated from the results; these are then discussed in terms of collision processes.…”