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Appl Spectrosc

Title:		A non-lensed fiber-optic resonance-enhanced multiphoton ionization probe
Author(s):		Chinni RC; Gold DM; Brown SB; Chang JT; Angel SM; Colston BW;
Address:		"University of South Carolina, Columbia, South Carolina 29208, USA"
Journal Title:		Appl Spectrosc
Year:		2004
Volume:		58
Issue:		9
Page Number:		1038 - 1043
DOI:		10.1366/0003702041959479
ISSN/ISBN:		0003-7028 (Print) 0003-7028 (Linking)
Abstract:		"We have developed a miniature fiber-optic probe with no focusing optics for in situ analysis of volatile organic compounds (VOCs). The probe uses an optical fiber to transmit a laser pulse to a vapor sample causing it to ionize adjacent to the fiber tip through a resonance-enhanced multiphoton ionization (REMPI) process. The distal end of the optical fiber is contained co-axially within 2-mm-inner-diameter stainless steel tubing that serves as an electrode. The electrode is biased at a high positive potential to collect electrons. The current generated is shown to be proportional over about two orders of magnitude to the concentration of the species ionized. Visible wavelength REMPI spectroscopy is used to determine probe sensitivities of 20 ppb (benzene) and 43 ppb (toluene). Designing the probe without focusing optics specifies an achromatic ionization region constant in size and position as the laser wavelength is scanned, which simplifies data collection and reduction. Focusing achromatic systems are discussed and the potential signal improvement is estimated"
Keywords:
Notes:		"PubMed-not-MEDLINEChinni, Rosemarie C Gold, Dave M Brown, Steve B Chang, John T Angel, S Michael Colston, Bill W Jr eng 2004/10/14 Appl Spectrosc. 2004 Sep; 58(9):1038-43. doi: 10.1366/0003702041959479"