4-1 chap. 7 (optical instruments), chap. 8 (optical atomic spectroscopy) general design of optical...
TRANSCRIPT
![Page 1: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/1.jpg)
4-1
Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy)
• General design of optical instruments• Sources of radiation• Selection of wavelength• Sample containers• Radiation Transducers• Instruments
• Optical instruments fundamental methods Absorption Fluorescence Phosphorescence Scattering Emission Chemical Luminenscence
![Page 2: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/2.jpg)
4-2
Optical methods• Similarities for differing methods over wavelength
range Stable source of radiation Transparent sample holder Isolation of region of interest Radiation detector
Transducer• Signal processor• Variations in setup depend upon detection of light
Linear for absorbance 90 degrees for fluorescence Emission and chemiluminescence source and
sample are same
![Page 3: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/3.jpg)
4-3
Apparatus
![Page 4: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/4.jpg)
4-4
Sources of radiation
• Materials Transparent
windows
![Page 5: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/5.jpg)
4-5
Sources of Radiation
• Continuum source Emission over a
large range Intensity can vary
with wavelength
• Line Source Intense emission of
discrete lines
![Page 6: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/6.jpg)
4-6
Light Sources
![Page 7: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/7.jpg)
4-7
Laser Sources
• Laser properties light amplification by stimulated emission
of radiation
High intensity
Narrow wavelength
Coherent* Can very pulse energy, wavelength* Combined with laser system
electronics for short lifetime measurements
![Page 8: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/8.jpg)
4-8
Laser Process
![Page 9: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/9.jpg)
4-9
Laser Process• Pumping
Excitation of lasing materialCrystal (ruby)Semiconducter (GaAs)DyeGas (Ar)
Spontaneous EmissionEmission of radiation in random direction
Stimulated EmissionExcited laser species interact with emitted radiation* Deexcitation of excited species
Photon emission energy same as spontaneous emitted photonCoherent emission
![Page 10: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/10.jpg)
4-10
Laser Dyes
![Page 11: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/11.jpg)
4-11
Population Inversion and Amplification
Need to highly populate excited state
![Page 12: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/12.jpg)
4-12
Three and four level transitions
Excitation to high state, transition to metastable state
![Page 13: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/13.jpg)
4-13
0
10
20
30
Wav
enu
mb
er (
103 c
m-1
)Absorption and fluorescence process of Cm3+
Optical Spectra
HGF
7/2A
Z 7/2
Fluorescence Process
Excitation
EmissionlessRelaxation
FluorescenceEmission
![Page 14: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/14.jpg)
4-14
![Page 15: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/15.jpg)
4-15
Wavelength Selectors
• Quality of selected wavelength based on full with at half maximum
![Page 16: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/16.jpg)
4-16
Filters
• Absorption filter Visible region Colored glass
or dye act as the filter
![Page 17: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/17.jpg)
4-17
Filters
• Interference filters Combination of constructive and
destructive interference Filter wavelength based on properties of
filter
Dielectric layer determines wavelength
![Page 18: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/18.jpg)
4-18
Filters• Constructive interference equations
n = 2dsin 90°, sin 1 n = 2d air = glass × = refractive index
n is order of interference
n
d 2
![Page 19: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/19.jpg)
4-19
Monochromators
• Allow selection of specific wavelengths over a scanned range IR, Visible, Ultraviolet
• Similar components Entrance slit
Rectangular optical image Collimating lens
Parallel beam of radiation Prism or grating
Selection of wavelength Focus element
Reforms image and places on focal plan Exit slit
Isolates desired wavelength
![Page 20: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/20.jpg)
4-20
Monochromators
Grating are more common in modern equipment Linear dispersion= variation in along plane ABD=Fdr/d, F= focal lengthD-1=d/nF=[nm/mm]
![Page 21: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/21.jpg)
4-21
Monochromator
• Can calculate i is incident r is reflection
• i is known
• d is from grating in nm i.e., 2000
lines/mm needs to be converted to nm/line
• n is generally 1
• Angle r must be defined to find
)sin(sin ridn
![Page 22: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/22.jpg)
4-22
Monochromator Slit
• Parameter that can be set • Controls light input• Resolution can be affected by slit width
Wavelength to be examined is considered Wider slits less resolution but may have
better signal
![Page 23: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/23.jpg)
4-23
Monochromator Slit
• Can calculate slit width based on experimental consideration Resolution difference of
wavelength to be examined
• Theoretical calculation Actually need narrower slit
width due to imperfections
11
)(*5.0
DDw resolutioneff
![Page 24: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/24.jpg)
4-24
Radiation Transducers
• Photon Transducers Photovoltaic cells Phototubes
e- emission from phosphor Photomultiplier
Cascade of electrons Photoconductors Photodiodes Charge-transfer
Si crystal collects charge due to absorption
![Page 25: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/25.jpg)
4-25
Phototube and Photomultiplier
105-107 electrons/photon
![Page 26: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/26.jpg)
4-26
Optical Atomic Spectroscopy• Optical Atomic Spectroscopy• Atomization Methods• Sample Introduction
• Optical Spectroscopy Elements converted to gaseous atoms or ions Measurements of atomic species
FluorescenceUV-Visible absorptionEmission
• Calculations can be made based on electron energy diagrams Transition between states
![Page 27: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/27.jpg)
4-27
Na and Mg energy levels
![Page 28: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/28.jpg)
4-28
Electronic Energy Symbols
• 2S+1LJ
• S is spin from unpaired e-
+ ½ L is written as S, P, D J=L+S
• Li= 1s22s1
L=0, S =+ ½ 2S1/2
![Page 29: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/29.jpg)
4-29
Atomic Emission Spectra
• Excitation of electrons Short lived Relaxation to ground state
Emission of photon* Visible range* Possible multiple lines
• Absorption spectroscopy Resonance due to transitions from ground
to excited state• Fluorescence can also occur
![Page 30: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/30.jpg)
4-30
Atomic Line Widths
• Broadening due to differing effects Uncertainty
vt• Line width due to Hg with lifetime of 2E-8s at
253.7 nm
![Page 31: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/31.jpg)
4-31
Line Widths
• Doppler Atom moves during radiation interaction
![Page 32: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/32.jpg)
4-32
Thermal effects
• Boltzmann equation
• Calculate Na atoms in 3p excited states to ground as 2500 K
• 3s to 3p transition is 3.37E-19J• P based on quantum states
3s has 2, 3p has 6
472.1)2500*2338.1
)1937.3exp(
2
61
E
KJKE
JE
N
N
o
j
![Page 33: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/33.jpg)
4-33
![Page 34: 4-1 Chap. 7 (Optical Instruments), Chap. 8 (Optical Atomic Spectroscopy) General design of optical instruments Sources of radiation Selection of wavelength](https://reader036.vdocument.in/reader036/viewer/2022062300/56649dac5503460f94a9ae79/html5/thumbnails/34.jpg)
4-34