Optimal spectral region for real-time monitoring of sub-ppm levels of water in phosphine using cavity ring-down spectroscopy

Published

January 1, 2004

Author(s)

Susan Y. Lehman, Kristine A. Bertness, Joseph T. Hodges

Abstract

We have utilized cavity ring-down spectroscopy (CRDS) to characterize the pressure and carrier gas effects on the shape of a water absorption line. The half-width at half-maximum (HWHM) pressure-broadening coefficient for the water line at 10687.36 cm^-1 was measured to be 58 ' 6 MHzkPa^-1 (0.20 ' 0.02 cm^-1 atm^-1) for water in phosphine (PH₃). This value is twice as large as the pressure-broadening coefficient for the same absorption transition in the case of water in air. Strong interference from neighboring PH₃ lines limits the sensitivity of the system in the region of this absorption line. We have also characterized the spectral neighborhood of several other water absorption transitions for the water-PH₃ system; these additional water-PH₃ CRDS spectra are presented. We have identified the spectral region around the water line at 10667.76 cm^-1 as optimal for CRDS measurements of the water-PH₃ system. Minimal interference from adjacent PH₃ absorption transitions in this region enables high-sensitivity, real-time measurements of trace water in bulk PH₃. Utilizing this water line, our CRDS apparatus has an estimated detection limit of 50 nmol/mol^-1 H₂O in PH₃.

Citation

Journal of Crystal Growth

Volume

261

Pub Type

Journals

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Keywords

cavity ring-down spectroscopy, phosphine, water

Citation

Lehman, S. , Bertness, K. and Hodges, J. (2004), Optimal spectral region for real-time monitoring of sub-ppm levels of water in phosphine using cavity ring-down spectroscopy, Journal of Crystal Growth, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=31438 (Accessed October 14, 2024)