Photoinduced nucleation: a novel tool for detecting molecules in air at ultra-low concentrations

Patent · Tue Jan 01 00:00:00 EST 2002

OSTI ID:874830

Katz, Joseph L ^[1]; Lihavainen, Heikki ^[2]; Rudek, Markus M ^[3]; Salter, Brian C ^[4]

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1. Baltimore, MD
2. Masala, FI
3. Bruchkoebel, DE
4. New Market, MD

A method and apparatus for determining the presence of molecules in a gas at concentrations of less than about 100 ppb. Light having wavelengths in the range from about 200 nm to about 350 nm is used to illuminate a flowing sample of the gas causing the molecules if present to form clusters. A mixture of the illuminated gas and a vapor is cooled until the vapor is supersaturated so that there is a small rate of homogeneous nucleation. The supersaturated vapor condenses on the clusters thus causing the clusters to grow to a size sufficient to be counted by light scattering and then the clusters are counted.

• Research Organization: Johns Hopkins Univ., Baltimore, MD (United States)
• DOE Contract Number: FG02-95ER62004
• Assignee: The United States of America as represented by the United States Department (Washington, DC)
• Patent Number(s): US 6469781
• OSTI ID: 874830
• Country of Publication: United States
• Language: English

Related Subjects

photoinduced
nucleation
novel
tool
detecting
molecules
air
ultra-low
concentrations
method
apparatus
determining
presence
gas
100
ppb
light
wavelengths
range
200
nm
350
illuminate
flowing
sample
causing
form
clusters
mixture
illuminated
vapor
cooled
supersaturated
rate
homogeneous
condenses
grow
size
sufficient
counted
scattering
light scattering
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