FEASIBILITY OF DOPPLER-FREE TWO-PHOTON SPECTROSCOPY FOR EXPLOSIVE VAPOR DETECTION - EQUIPMENT SYSTEMS IMPROVEMENT PROGRAM

• NCJ Number: 36749
• Author(s): J A GELBWACHS; C F KLEIN; J E WESSELL
• Date Published: 1976
• Length: 57 pages
• Contract Number(s): J-LEAA-025-73
• Sponsoring Agency: US Dept of Justice; US Dept of Justice NIJ Pub
• Corporate Author: Aerospace Corporation
• Sale Source: National Institute of Justice/
• Publication Type: Report (Study/Research)
• Language: English
• Country: United States of America

Annotation

THIS TECHNIQUE ATTEMPTS TO ELIMINATE THE MAJOR DISADVANTAGE OF NON-SPECIFIC EXPLOSIVES VAPOR DETECTION CAUSED BY BROADENING OF THE ABSORPTION BANDS BY RELYING ON THE SENSITIVITY OF OPTICAL METHODS OF DETECTION.

Abstract

SPECIFICALLY, THIS TECHNIQUE ELIMINATES THE DOPPLER BROADENING CAUSED BY THE RANDOM MOTION OF MOLECULES IN THE GAS PHASE. A TWO-PHOTON SPECTROMETER WAS ASSEMBLED AND IT WAS DEMONSTRATED FOR THE FIRST TIME THAT THE METHOD IS APPLICABLE TO THE DETECTION OF COMMONLY OCCURRING MOLECULES. THE PARAMETERS REQUIRED TO DETERMINE THE TWO-PHOTON DETECTION LIMITS WERE MEASURED USING AN APPROPRIATE LASER SYSTEM. IT WAS SHOWN THAT WITH THE NEW METHOD TYPICAL MOLECULES SUCH AS BENZENE AND NITRIC OXIDE SHOULD BE DETECTABLE WITH HIGH SENSITIVITY EVEN IN THE PRESENCE OF OTHER MOLECULES. HOWEVER, DETECTION SENSITIVITY FOR EXPLOSIVE VAPORS WAS FOUND TO BE INADEQUATE BECAUSE THE MOLECULES DO NOT FLUORESCE EFFICIENTLY. IT WAS SHOWN THAT FOR REPRESENTATIVE EXPLOSIVE MOLECULES THE OPTICAL ABSORPTION BANDS REMAIN BROAD EVEN WHEN THE DOPPLER BROADENING IS ELIMINATED. (AUTHOR ABSTRACT)...PLO