High sensitivity detection techniques with microphones: a laser optoacoustic approach to the detection of ultra trace quantities of carcinogens and pollutants

Thesis/Dissertation · Tue Jan 01 04:00:00 EST 1985

OSTI ID:5944839

Choi, J G

The optoacoustic effect has been investigated as a detection means for ultra trace quantities of environmental carcinogens and pollutants. Three distinct approaches for developing high sensitivity detectors are described. The first utilizes a laser schlieren microphone, where a low-power He-Ne laser beam is defected by a reflecting diaphragm mounted on a Helmholtz resonator. The mathematical description and experimental results of the laser schlieren microphone show that the system responds linearly to optoacoustic signals. The second approach described couples a specially designed optoacoustic detector with a gas chromatograph for the detection of carcinogens. A small volume Helmholtz resonator has been developed to increase the detection sensitivity of the system for use with gas chromatography, eliminating the problems associated with artificial broadening of the peaks eluting from the chromatography column. A totally new approach to trace detection methods using chemical amplification of the optoacoustic effect is also described. The recombination of Cl radicals from the photodissociation of Cl/sub 2/ liberates heat producing a pressure increase of optoacoustic effect. When hydrogen is added to the photodissociated Cl/sub 2/, the evolution of heat in the system takes place through rapid and highly exothermic chain reactions. As a result of the large number of chain propagation cycles prior to termination of the chain reactions, the optoacoustic signal caused by the heat release initiated by the radiation far exceeds the amount of energy actually absorbed from the light beam.

• Research Organization: Brown Univ., Providence, RI (USA)
• OSTI ID: 5944839
• Country of Publication: United States
• Language: English

Related Subjects

500200* -- Environment
Atmospheric-- Chemicals Monitoring & Transport-- (-1989)
510200 -- Environment
Terrestrial-- Chemicals Monitoring & Transport-- (-1989)
520200 -- Environment
Aquatic-- Chemicals Monitoring & Transport-- (-1989)
54 ENVIRONMENTAL SCIENCES
ACOUSTIC DETECTION
ACOUSTIC MEASUREMENTS
ACOUSTIC MONITORING
CARCINOGENS
CHARGED PARTICLE DETECTION
CHLORINE
CHROMATOGRAPHY
DESIGN
DETECTION
ELECTRONIC EQUIPMENT
ELEMENTS
ENERGY
EQUIPMENT
GAS CHROMATOGRAPHY
GAS LASERS
HALOGENS
HEAT
HELIUM-NEON LASERS
LASERS
MEASURING INSTRUMENTS
MONITORING
MONITORS
NONMETALS
POLLUTANTS
RADIATION DETECTION
RESONATORS
SEPARATION PROCESSES
TRACE AMOUNTS