Spectroscopy, continued

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Spectroscopy, continued
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• Continuum
• Thermal radiation

Planck
Wien
S ? T4
Stefan-Boltzmann
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• Continuum
• Thermal radiation
• Bremsstrahlung (free-free)
• Free-bound, bound-free
• Synchrotron
• Multi-temperature population

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Line formation
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Line emission
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Line absorption
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Spectral lines delta functions? Energies are
discrete, right?
Heisenberg uncertainty ? non-zero natural line
width
But also, what else affects the width/structure
of the spectral line?
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• Observing
• Dispersive element prism/grating/Bragg crystal
• Dispersion, resolution
• Detection
• Signal/noise ratio
• Ghosts
• Curvature

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• Reflections from crystal lattice planes result in
  interference, yielding monochromatic light.
• What good is monochromatic? We wanted a
  spectrum.
• Vary the angle!

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Na
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If y.jgt0, j-increases when q increases.
(a, m, l, and j constant)
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curvature is does not depend on parameters of
grating
qq
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prism
grating

• ghosts (due to periodic variations in gratings
  spacing)
• Lyman (near spectral line)
• Rowland (at large distance)

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Order overlap
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Hg
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Order overlap
Cross-dispersion!
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Other observational considerations

• Slit-filling
• Multi-slit
• Slitless

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