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Absolute and relative isotope abundances measured by tunable diode laser spectroscopy

Thesis/Dissertation ·
OSTI ID:5205340

The potential for measuring absolute and relative isotope abundances by high resolution spectroscopy with tunable diode lasers as sources was studied. In order to achieve the sensitivity necessary to determine the absolute abundances of molecules containing long-lived radionuclides such as /sup 14/C and /sup 129/I, a resonant spectrophone based on the photoacoustic effect was used for detection. For safety, NH/sub 3/ was used as a sample with air as a buffer gas when characterizing the performance of the TDL-spectrophone system. Frequency modulation of the TDL was employed. The optimum operating pressure was found to be 6.6 kPa(50 Torr). Substitution of Kr as a buffer gas yielded a fourfold increase in signal. It is estimated that with currently available TDLs a photoacoustic spectrometer should be capable of detecting /sup 14/CO/sub 2/ and CH/sup 129/I at the levels present in nuclear reactor containment gases. An isotope shift of CH/sub 3//sup 129/I relative to CH/sub 3//sup 127/I in the nu/sub 6/ band of (0.0135 +/- 0.0006) cm/sup -1/ was measured by TDL linear absorption spectroscopy.

Research Organization:
Wesleyan Univ., Middletown, CT (USA)
OSTI ID:
5205340
Country of Publication:
United States
Language:
English