Optical Spectroscopy Instrumentation Design
177
252
35000
30000
25000
20000
15000
10000
5000
0
253
254
255
Wavelength (nm)
Intensity
363
30000
25000
20000
15000
10000
5000
0
365
367
364
366
368
Wavelength (nm)
434
436
435
437 438
Wavelength (nm)
Intensity
18000
16000
14000
10000
12000
8000
4000
6000
2000
0
Intensity
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.
repeatability in scanning should be equal to or exceed 0.2 nm. Figure 5.19 highlights the
importance of scanning reproducibility.
23,000
22,000
21,000
20,000
19,000
18,000
17,000
16,000
15,000
14,000
13,000
Signal Value
Signal Value
12,000
23,400
23,200
23,000
22,800
22,600
22,400
22,200
22,000
21,800
21,600
21,400
11,000
10,000
9,000
8,000
7,000
6,000
5,000
4,000
3,000
2,000
1,000
253
2 54
Step
255
253.55 253.6 253.65 253.7
253.5
253.75 253.8 253.85 253.9 253.95
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 wavelength scanning.