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Spectroscopic Light SourcesPowerPoint Presentation

Spectroscopic Light Sources

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## PowerPoint Slideshow about ' Spectroscopic Light Sources' - bree-brewer

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### Continuum Sources

Emit radiation over a broad spectral range.

Continuum in Wavelength, not necessarily in time.

Most of these are “black body emitters. The spectral range depends upon the temperature of the black body.

Optical material containing an absorber that permits transmission only at certain wavelengths

Dl

Dl = f × Da = dx/dλ

where:

f = focal length

(of monochromator)

x = distance

(along focal plane)

(s or Δλ)

s = RLD × w

where:

w = slit width (mm)

s in nm

Reciprocal Linear

Dispersion (RLD)

RLD = Dl-1

=dλ/dx

nm/mm

Si: 3s23p2

Covalent Bonds in Solid

Therefore 1/2–filled

sp3

ΔE ≤ 2.5 eV

(semiconductor)

3. Si Photodiode

4 electrons fill a valence band at 0K

At higher T an electron can move to conduction band

Leaving a positive hole behind (both are mobile)

element (As or Sb) results

in extra electrons (n-type).

Doping with a group 3

element (In, Ga) results

in extra holes (p-type)

3. Si Photodiode

Forward bias (not very useful for spectroscopy)

Depletion zone at the

junction.

Photons may eject

electrons and form

holes

Current proportional

to number of photons

3. Si Photodiode

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