Introduction to Spectroscopy and its Applications to Art and History

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Introduction to Spectroscopy and its Applications
to Art and History
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What is Spectroscopy?

• Spectroscopy is the use of electromagnetic (think
  light) radiation to perform a chemical analysis
  of a sample.
• Question for thought
• What is electromagnetic radiation / light?
• What regions of the electromagnetic spectrum do
  we use?
• What information can we get from light?

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Electromagnetic Radiation

• Mathematical theory that describes all forms of
  radiation as oscillating (wave-like) electric and
  magnetic fields

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Wave Properties

• Wavelength (l) distance between consecutive
  crests or troughs
• Frequency (n) number of waves that pass a given
  point in some unit of time (1 sec)
• -units of frequency 1/time such as 1/s s-1
  Hz
• Amplitude (A) the maximum height of a wave
• Nodes points of zero amplitude
• -every l/2

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What is Spectroscopy?

• Spectroscopy is the use of electromagnetic (think
  light) radiation to perform a chemical analysis
  of a sample.
• Question for thought
• What is electromagnetic radiation / light?
• What regions of the electromagnetic spectrum do
  we use?
• What information can we get from light?

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Electromagnetic Spectrum
Which region to use depends on what we are
looking at
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What is Spectroscopy?

• Spectroscopy is the use of electromagnetic (think
  light) radiation to analyze a sample.
• Question for thought
• What is electromagnetic radiation / light?
• What regions of the electromagnetic spectrum do
  we use?
• What information can we get from light?

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Continuous Spectrum vs Line Spectra
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• Anything with color absorbs light.
• What we see, is the light that is not absorbed

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• An absorption spectrum is formed by shining a
  beam of white light through a sample of gas.
• Absorption spectra indicate the wavelengths of
  light that have been absorbed.

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Atomic Spectra

• Every element has a unique spectrum
• -Thus we can use spectra to identify elements.
• -This can be done in the lab, with stars, in
  fireworks, etc.

H
Hg
Ne
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How are these lines generated
absorbance
fluorescence
Gemstones and Minerals
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Where are X-rays?
Later we will use an instrument that uses x-rays,
like at the doctors Office, to provide us
chemical information about a sample (i.e. art
work) We cannot see x-rays.
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Each element as a unique XRF spectrum
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We can false color the emitted X-rays based on
the element signature
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• How is this useful to a student of Art or
  History?
• Can be used to detect forgery
• Determine how/when a painting or artifact was
  made
• Other?

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Look at the painting to the right. This grassy
field has something interesting buried under it.
Looking that the painting with X-ray and IR light
reveals the following image
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With X-rays we can look at the concentration of
various elements
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Recreating the original painting