The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Feb. 02, 1999
Filed:
Feb. 28, 1997
Rosario C Sausa, Bel Air, MD (US);
Josef B Simeonsson, Iowa City, IA (US);
The United States of America as represented by the Secretary of The Army, Washington, DC (US);
Abstract
A method and apparatus is provided for real-time detection of trace amounts of atmospheric and tropospheric halogen-containing compounds. The present invention can be used either for in situ detection or remote sensing. A laser is employed to induce photofragmentation of the halogenated molecules and facilitate detection of the characteristic atom fragment by stimulated emission spectrometry. For brominated compounds, the output of a single laser is tuned to the strong two-photon 4p.sup.4 5p .sup.4 D.degree..sub.3/2 .rarw.4p.sup.5 2 P.degree..sub.3/2 transition of Br at 260.634 nm. The Br atoms are subsequently detected by stimulated emission (SE) via the 4p.sup.4 5p .sup.4 D.degree..sub.3/2 .fwdarw.4p.sup.4 5s .sup.4 P.sub.5/2 transition at 844 nm. For comparison, the laser-induced fluorescence (LIF) signal at the same wavelength is also monitored. The SE signal is distinct from the fluorescence in that it is coherent, bidirectional, and propagates coaxially with the laser beam. As a result of photophysical amplification, it is approximately two orders of magnitude greater than the LIF signal. The present invention has been demonstrated for trace detection of CHBr.sub.3 and CHClBr.sub.2 in N.sub.2 or air at total gas pressures of 1-760 Torr. Detection limits are in the parts-per-million range. The absorption cross section of the two-photon 4p.sup.4 5p .sup.4 D.degree..sub.3/2 .rarw.4p.sup.5 2 P.degree..sub.3/2 transition is estimated to be 3.8.times.10.sup.-43 cm.sup.4.