THE OPTO-ACOUSTIC EFFECT: REVIVAL OF AN OLD TECHNIQUE FOR MOLECULAR SPECTROSCOPY

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1973

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Ohio State University

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Using a monochromator-lamp combination, phase sensitive detection and a sensitive foil electret microphone, we have constructed an opto-acoustic spectrometer which detects heat released by radiationless transitions following absorption in the 10 000 - 2000 \AA region. The technique is applicable with high sensitivity to absorptions in gases and in solids. Spectra of substances in the gas phase provide information that complements luminescence and photochemical studies. Comparison of conventional absorption spectra and opto-acoustic spectra clearly show the onset of photochemical processes, such as dissociation. Using phase sensitive detection the rates of radiationless relaxation processes may be studied. Spectra of $NO_{2}, I_{2}$ and $SO_{2}$ will be shown to illustrate the use of opto-acoustic spectra to study radiationless relaxation processes.

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Author Institution: Bell Laboratories

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