Transcript Lecture Notes 3

Components of
Optical Instruments
or
What’s inside that spectrometer?
Components of Optical Instruments
Source
Wavelength Selector
Sample
Detector
Signal Processor
Readout
Emission Flame Photometer
Flame Atomic Absorption Spectrometer
Absorption Spectrometer
Fluorescence and/or Scattering Spectrometer
Components of
Optical Instruments
Emission Flame Photometer
Source
Sample
Wavelength Selector
Detector
Signal Processor
Readout
Components of
Optical Instruments
Flame Atomic Absorption Spectrometer
Source
Wavelength Selector
Sample
Detector
Signal Processor
Readout
Components of
Optical Instruments
Absorption Spectrometer
Source
Sample
Wavelength Selector
Detector
Signal Processor
Readout
Components of
Optical Instruments
Fluorescence and/or Scattering Spectrometer
Sample
Wavelength Selector
0-90o
Source
Detector
Signal Processor
Readout
Components of Optical Instruments
Fig. 7-2, pg. 145 ”(a) Construction materials
Components of Optical Instruments
Fig. 7-2, pg. 145 ”(b) wavelength selectors for spectroscopic
instruments."
Components of Optical Instruments
Components of Optical Instruments
Sources
YOU
TELL
ME!
Sources of radiation
Blackbody Radiation:
MAX
I
1

T
Etotal  T
4

Monochromator – can vary wavelength – scan
spectrum Prism – shorter wavelengths dispersed more
Grating – Dispersion of light is linear in 
Types of gratings – most common – echellette
UV-visible  1200 –1400 grooves /mm
IR  hundreds of grooves/mm
Holographic Gratings – made by laser technology –
very cheap, easy to make and very reproducible, can produce up too 6000 grooves/mm.
Width of Slits
Effective Bandwidth –
eff =
wD-1

d
D 

y nF
1
reciprocal linear dispersion, the inverse of the linear
dispersion (D, mm/nm), which is the spreading of the light
by a monochromator grating.
d is the distance between blazes on the grating, and F is
the focal length of the monochromator.
w= slitwidth
when Dy = w,  is the effective bandwidth
Example: To tell the difference between 589.6 and 589.0
nm light, what slitwidth would be required?