A Non-Lensed Fiber-Optic Resonance-Enhanced Multiphoton Ionization Probe

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

Resonance-enhanced multiphoton ionization REMPI Fiber optic Volatile organic compounds Electrode Achromatic

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References

Neff

J. M.

, Chem. Eng. Prog. 83, 27 (1987).

Brown

Milanovich

F. P.

Kyle

and Myrick

M. L

, Rev. Sci. Instrum. 70, 3735 (1999).

Cohen

R. M.

Bryda

A. P.

Shaw

S. T.

and Spalding

C. P

, Ground Water Monit. R. 12, 132 (1992).

Platt

, Fresenius J. Anal. Chem. 340, 6 (1991).

Johnson

P. M.

, Acc. Chem. Res. 13, 20 (1980).

Cullum

B. M.

Shealy

S. K.

and Angel

S. M

, Appl. Spectrosc. 53, 1646 (1999).

Shang

Q. Y.

Moreno

R. D.

and Bernstein

E. R

, J. Chem. Phys. 98, 3703 (1993).

Clark

Ledingham

K. W. D.

Marshall

Sander

and Singhal

R. P

, Analyst (Cambridge, U.K.) 118, 601 (1993).

Nesselrodt

D. R.

and Baer

, Anal. Chem. 66, 2497 (1994).

10.

Nesselrodt

D. R.

Potts

A. R.

and Baer

, J. Phys. Chem. 99, 4458 (1995).

11.

Sin

C. H.

Tembreull

and Lubman

D. M

, Anal. Chem. 56, 2776 (1984).

12.

Buma

W. J.

Kohler

B. E.

and Song

, J. Chem. Phys. 94, 4691 (1991).

13.

Cornish

T. J.

and Baer

, Phys. Chem. 94, 2852 (1990).

14.

Meier

and Kohse-Hiinghaus

, Chem. Phys. Lett. 142, 498 (1987).

15.

Mallard

W. G.

Miller

J. H.

and Smyth

K. C

, J. Chem. Phys. 76, 3483 (1982).

16.

Tjossem

P. J. H.

and Cool

T. A

, Chem. Phys. Lett. 100, 479 (1983).

17.

Cool

T. A.

, Appl. Opt. 23, 1559 (1984).

18.

Lichtin

D. A.

Zandee

and Bernstein

R. B

, in Lasers in Chemical Analysis, Hieftje

Travis

and Lytle

, Eds. (Humana, Clifton, NJ, 1981), Chap. 6.

19.

Hurst

G. S.

Payne

M. G.

Kramer

J. D.

and Young

J. P

, Rev. Mod. Phys. 51, 767 (1979).

20.

Bjorklund

G. C.

Ausschnitt

C. P.

Freeman

R. R.

and Storz

R. H

, Appl. Phys. Lett. 33, 54 (1978).

21.

Payne

M. G.

Chen

C. H.

Hurst

G. S.

and Foltz

G. W

, Adv. At. Mol. Phys. 17, 229 (1981).

22.

Lubman

D. M.

and Kronick

M. N

, Anal. Chem. 54, 660 (1982).

23.

Inoue

Gridin

V. V.

Ogawa

and Schechter

, Anal. Chem. 70, 4333 (1998).

24.

Gridin

V. V.

Inoue

Ogawa

and Schechter

, Instrum. Sci. Technol. 28, 131 (2000).

25.

Morrison

R. J. S.

and Grant

E. R

, J. Chem. Phys. 75, 49 (1981).

26.

Bjorklund

G. C.

Freeman

R. R.

and Storz

R. H

, Opt. Commun. 31, 47 (1979).

27.

Sirkin

E. R.

and Haas

, Appl. Phys. 25, 253 (1981).

28.

Rockney

B. H.

Cool

T. A.

and Grant

E. R

, Chem. Phys. Lett. 87, 141 (1982).

29.

Goldsmith

J. E. M.

, Opt. Lett. 7, 437 (1982).

30.

Smyth

K. C.

and Mallard

W. G

, J. Chem. Phys. 77, 1779 (1982).

31.

Krogh-Jespersen

Rava

R. P.

and Goodman

, Chem. Phys. 44, 295 (1979).

32.

Cool

T. A.

and Williams

B. A

, Combust. Sci. Technol. 82, 67 (1992).

33.

Bunkin

F. V.

and Prokhorov

A. M

, Sov. Phys. J.E.T.P. 19, 739 (1964).

34.

Marshall

Ledingham

K. W. D.

and Singhal

R. P

, Analyst (Cambridge, U.K.) 120, 2069 (1995).

35.

Koppel

Cederbaum

L. S.

and Domcke

, J. Chem. Phys. 89, 2023 (1988).

36.

Voumard

Zenobi

and Zhan

, J. Phys. Chem. 99, 11722 (1995).

37.

Speiser

and Jortner

, Chem. Phys. Lett. 44, 399 (1976).

38.

Spieser

and Kimel

, Chem. Phys. Lett. 7, 19 (1970).

39.

Lin

S. H.

Fujimura

Neusser

H. J.

and Schlag

E. W

, in Multiphoton Spectroscopy of Molecules (Academic Press, Orlando, FL, 1984), pp. 89–99.