Lecture 8: Volume Interactions

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Friday, 28 January 2010
Lecture 8 Volume Interactions
Reading
Ch 1.8 http//speclib.jpl.nasa.gov/ Major
spectral features of minerals (p. xiii-xv), from
Infrared (2.1-25 mm) Spectra of Minerals, J W
Salisbury et al., 1991 ( class
website) Optional reference reading Roger
Clarks tutorial on spectroscopy (class website)
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What was covered in the previous lecture

• Wednesdays lecture
• 1) reflection/refraction of light from surfaces
• (surface interactions)
• Todays lecture
• 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

• LECTURES
• Jan 05 1. Intro
• Jan 07 2. Images
• Jan 12 3. Photointerpretation
• Jan 14 4. Color theory
• Jan 19 5. Radiative transfer
• Jan 21 6. Atmospheric scattering
• Jan 26 7. Lamberts Law previous
• Jan 28 8. Volume interactions today
• Feb 02 9. Spectroscopy
• Feb 04 10. Satellites Review
• Feb 09 11. Midterm
• Feb 11 12. Image processing
• Feb 16 13. Spectral mixture analysis
• Feb 18 14. Classification
• Feb 23 15. Radar Lidar
• Feb 25 16. Thermal infrared
• Mar 02 17. Mars spectroscopy (Matt Smith)
• Mar 04 18. Forest remote sensing (Van Kane)

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Spectral radiance (W/m2/nm/sr)
Wavelength (nm)
Spectral radiance (W/m2/nm/sr)
Spectral radiance (W/m2/nm/sr)
Wavelength (nm)
Wavelength (nm)
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• Interaction of Energy and Matter
• What causes absorption features in spectra?
• Three effects of radiant energy on matter
• Rotational absorption (gases)
• Electronic absorption
• Vibrational absorption

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Rotational Processes Photons striking free
molecules can cause them to rotate. The
rotational states are quantized, and therefore
there are discrete photon energies that absorbed
to cause the molecules to spin. Rotational
interactions are low-energy interactions and the
absorption features are at long infrared
wavelengths.
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Electronic Processes Isolated atoms and ions
have discrete energy states. Absorption of
photons of a specific wavelength causes a change
from one energy state to a higher one. Emission
of a photon occurs as a result of a change in an
energy state to a lower one. When a photon is
absorbed it is usually not emitted at the same
wavelength. The difference is expressed as heat.
Four types Crystal Field Effects Charge
Transfer Absorptions Conduction Bands Color
Centers
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Electronic Processes Crystal Field Effects The
electronic energy levels of an isolated ion are
usually split and displaced when located in a
solid. Unfilled d orbitals are split by
interaction with surrounding ions and assume new
energy values. These new energy values
(transitions between them and consequently their
spectra) are primarily determined by the valence
state of the ion (Fe 2, Fe3), coordination
number, and site symmetry.
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http//img.alibaba.com/photo/50502613/Europium_Oxi
de.jpg
Electronic transitions, crystal field effects
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Electronic Processes Charge-Transfer
Absorptions Absorption bands can also be caused
by charge transfers, or inter-element transitions
where the absorption of a photon causes an
electron to move between ions. The transition
can also occur between the same metal in
different valence states, such as between Fe2
and Fe3. Absorptions are typically strong. A
common example is Fe-O band in the uv, causing
iron oxides to be red.
http//en.wikipedia.org/wiki/ImageHematite.jpg
http//www.galleries.com/minerals/silicate/olivine
/olivine.jpg
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Mg
Diopside
Fe
(Mg,Fe)2SiO4
http//www.gemstone.org/images/01/Stones_Diopside.
jpg
MgCaSi2O6
Electronic transitions (Fe2, Fe3), charge
transfer (Fe-O)
(Mg,Fe)SiO3
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Electronic Processes Conduction Bands In metals
and some minerals, there are two energy levels in
which electrons may reside a higher level called
the "conduction band," where electrons move
freely throughout the lattice, and a lower energy
region called the "valence band," where electrons
are attached to individual atoms. The yellow
color of gold and sulfur is caused by
conduction-band absorption.
Sulfur
Gold
www.egyptcollections.com
web.syr.edu/iotz/Gallery.htm
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Conduction band processes
http//www.mii.org/Minerals/Minpics1/Cinnabar.jpg
HgS
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Vibrational Processes The bonds in a molecule or
crystal lattice are like springs with attached
weights the whole system can vibrate. The
frequency of vibration depends on the strength of
each spring (the bond in a molecule) and their
masses (the mass of each element in a molecule).
For a molecule with N atoms, there are 3N-6
normal modes of vibrations called fundamentals.
Each vibration can also occur at multiples of the
original fundamental frequency (overtones) or
involve different modes of vibrations
(combinations). In general, a molecule with N
atoms has 3N-6 normal modes of vibration
but linear molecules have only 3N-5 normal
modes of vibration as rotation about its
molecular axis cannot be observed.
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vibrational interactions
gases
Vibration-higher energy than rotation Vibration -
harmonic oscillators stretching, bending
Molecular vibrations cause the multiple
absorption bands
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n1
n3
n2
Vibrational - rotational modes combine to produce
complex spectra with sharp bands
Vibrational modes produce simple spectra
Vibration in water molecules
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X-OH vibrations in minerals band position in
mica shifts with composition
www.pitt.edu/.../1IgneousMineralz/Micas.html
KAl2(AlSi3O10)(F,OH)2
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Band position in carbonate minerals shifts with
composition
MgCO3
CaCO3
www.galleries.com/.../calcite/calcite.htm
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Si-O bond vibrational resonance
O
O
Si
QUARTZ
O
O
SiO2
www.pitt.edu/.../Quartz/QuartzCrystal.jpg
Thermal infrared
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Examples of mineral spectra
Fe2O3
a-FeO(OH)
KFe3(SO4)2(OH)6
http//www.news.cornell.edu/photos/jarosite300.jpg
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Spectra of common Earth-surface materials
www.gfmer.ch/.../Papaver_somniferum.htm
www.oznet.ksu.edu/fieldday/kids/soil_pit/soil.htm
www.bigwhiteguy.com/photos/images/814.jpg
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Next lecture 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