FREQUENCY MODULATED VISIBLE LASER ABSORPTION MEASUREMENT OF THE HF 4TH OVERTONE
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Date
1984
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Ohio State University
Abstract
With the recent application of frequency modulation techniques to tunable dye laser absorption $spectroscopy^{1}$ by Bjorklund, the detection of small concentrations of very weakly absorbing atomic and molecular species has been made possible. We have extended this work to investigate the sensitivity of FM spectroscopy. We have used a single frequency tunable dye laser, frequency modulated at 250 MHz, to scan the R(4) branch of the $HF X {^{1}}\Sigma^{+}(v=0\rightarrow v=5)$ transition ($\Delta E = 18225 cm^{-1}$) in absorption. Line shape profiles were obtained with $\pm 0.0002 cm^{-1}$ resolution over the pressure range 1-500 torr using only a 26 cm single pass optical configuration. From an analysis of the spectra, the Einstein A coefficient and the dipole-dipole broadening coefficient were obtained. At the present state of development, sensitivity is about four orders of magnitude greater than usual absorption techniques. This work demonstrates the potential of a technique which can retrieve high resolution lineshape and intensity information from atomic and molecular processes inaccessible to traditional methods. The talk will discuss experimental results and future implications of FM spectroscopy to chemistry and physics.
Description
$^{1}$ Gary C. Bjorklund, Optics Letters 5 (1), 15 (1980).
Author Institution: United Technologies Corporation, Research Center Silver Lane
Author Institution: United Technologies Corporation, Research Center Silver Lane