Geoscience Reference
In-Depth Information
35000
30000
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30000
25000
14000
25000
20000
12000
20000
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0
0
0
434
435
436
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438
252
253
254
255
363
364
365
366
367
368
Wavelength (nm)
Wavelength (nm)
Wavelength (nm)
Figure 5.18. Typical resolution plots at 253.6, 365.0, and 435.8 nm showing optical resolutions of
better than 0.1 nm FWHM. 435.8 nm is a common wavelength for manufacturers to specify spectral
resolution, usually using a 1200 g/mm grating.
23,000
22,000
21,000
20,000
19,000
18,000
17,000
16,000
15,000
14,000
13,000
23,400
23,200
23,000
22,800
22,600
12,000
22,400
11,000
10,000
9,000
8,000
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4,000
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1,000
22,200
22,000
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253
254
255
253.5
253.55253.6 253.65253.7
253.75253.8 253.85253.9 253.95
Step
Step
Figure 5.19. Determination of scanning reproducibility by repetitive scanning of the 253.6 nm Hg
line. Typical examination of the peak feature indicates excellent reproducibility (>0.2 nm) in wave-
length scanning.
as a means to control the light level presented to the analysing detector, rather than select
an appropriate neutral density filter. Simplistically, it is quite easy to derive this empiri-
cally by adjusting the slit width and observing the resultant spectra in terms of its intensity
and spectral shape. However, great care must be taken when using this approach such that
important spectral information is not lost. For example, if the spectra show structure, such
