Lecture 9: Spectroscopy

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Tuesday, 3 February
Lecture 9 Spectroscopy
Reading assignment Ch 7, Digital Image
Processing -- 7.1 7.76 (p. 482 545)
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Discussion 1) reflection/refraction of light
from surfaces (surface interactions) 2) volume
interactions - resonance - electronic
interactions - vibrational interactions 3)
spectroscopy - continuum vs. resonance bands -
spectral mining - continuum analysis 4)
spectra of common Earth-surface materials
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Spectra vary with composition
Minerals
Ices
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Molecular vibration modes in silicates affect the
thermal infrared
Thermal infrared
silicates
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Reflectance spectrum of SiO2 in the TIR
QUARTZ
The doubled peak is due to crystallographic
asymmetry (hexagonal) in quartz
The silica tetrahedron is distorted in quartz
the Si-O bond down the c-axis has a different
length than it does across it
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Phase affects spectra
Bands dont broaden much as ice turns to
water Band centers shift subtly Amount of
absorption increases with optical length d in
Beers law (e-kd) there are no grain interfaces
in water. This is a particle size affect
Low water content
Ice liquid transition In water
High water content
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Particle size affects spectra
Coarse particles spectra dominated by
absorption inside grains
Fine particles spectra dominated by surface
reflection
High surface/volume ratio Path is shorter
Low surface/volume ratio Average optical path is
long
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Particle size affects spectra
Pyroxene
H2O
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Spectral resolution multispectral remote
sensing vs. imaging spectroscopy
Imaging spectroscopy is more likely to resolve
absorption bands
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Spatial resolution also affects spectra (by
mixing)
Areal (checkerboard) mixing additive Intimate
mixing subtractive
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Intimate mixing can be highly non-linear
Adding highly absorptive charcoal greatly reduces
the optical path length (d in Beers Law
e-kd) A small amount has a large effect Larger
amounts have diminishing effect
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Spectroscopy considerations - continuum vs.
resonance bands
Absorption bands are measured relative to the
continuum that is supposed to be the spectrum
in the band was not present
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Discussion 1) reflection/refraction of light
from surfaces (surface interactions) 2) volume
interactions - resonance - electronic
interactions - vibrational interactions 3)
spectroscopy - continuum vs. resonance bands -
spectral mining - continuum analysis 4)
spectra of common Earth-surface materials
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Spectra of common Earth-surface materials
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Spectra of common Earth-surface materials
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Spectra of common Earth-surface materials
Chlorophyll absorption
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Leaf structure and its relation to spectra
Absorption band in red chlorophyll
pigment Reflective NIR scattering in the
prismatic leaf cells SWIR absorption absorption
by leaf water
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Next Class Satellites Review for Midterm