Abstract

A cylindrical sample cell is adapted to the problem of increasing the scattered-light signal from an optically thin liquid sample. The ends of the cylinder are coated with specularly reflecting aluminum to increase the signal by reflecting the stimulating light beam through the medium multiple times. The circumference of the cylinder is similarly coated to increase the fraction of the emitted light that is collected and sent into the slit of a spectrometer. Such a cell can greatly increase the signal measured by an analysis system without any modifications to the system.

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References

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2008

2007

1996

1995

1988

1975

Angel, S. M.

Berger, A. J.

Brennan, J. F.

Carter, J. C.

Chan, J. W.

Dasari, R. R.

Durig, J. R.

Feld, M. S.

Furic, K.

Itzkan, I.

Kebabian, P. L.

Lucke, R. L.

May, A. D.

McManus, J. B.

Pacheco, M. T. T.

Pearman, W. F.

Samson, J. A. R.

J. A. R. Samson, Techniques of Vacuum Ultraviolet Spectroscopy (Pied Publications, 1967).

Tanaka, K.

Witkowicz, T.

Zahniser, M. S.

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Figures (4)

Fig. 1
Fig. 1

Cylindrical (or square cross section) sampling cells seen from the side. Laser beams enter and (may) exit the cells through uncoated regions of their ends and are reflected from coated regions. In (a) the ends of the cell are parallel and the beam reflects back and forth in the cell until it fades out (9 reflections are shown). In (b) the right end is slightly tilted with respect to the left, about an axis perpendicular to the page. By this means the beam can be concentrated in a smaller region of the cell. Depending on the geometry, it may then exit the cells as shown or reflect until it fades out.

Fig. 2
Fig. 2

A cylinder of radius R, seen from one end, contains an axial source region of radius r and is coated with reflective aluminum except for a narrow strip (also seen end-on) along the top that forms the entrance slit of a spectrometer. Example ray 1 from an arbitrary point in the source region exits directly through the slit. Example ray 2 originates at the edge of the source region and is tangent to it. This ray reflects off the surface of the cylinder, then exits through the slit. The angle between the ray and the surface normal is θ and the reflected ray is tangent to the circle of radius r. Example ray 2 is also tangent to the source region, but exits directly through the slit. Observe that all rays exit the slit within the angle defined by rays 2 and 2 .

Fig. 3
Fig. 3

Example rays 3 and 4 are reflected twice and three times, respectively, before exiting the cylinder.

Fig. 4
Fig. 4

Side view of tube. Example ray 5 has a direction component along the axis of the tube and reflects four times with its azimuthal angle θ (see Figs. 2, 3) changing at each reflection. After the fourth reflection, it exits through the slit.

Equations (3)

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M 1 = 1 + ρ + ρ 2 + = 1 1 ρ .
D = 2 F d or d D = 1 2 F ,
M 2 1 + ρ + ρ 2 + = 1 1 ρ ,

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