Fluorescence and Phosphorescence

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Fluorescence and Phosphorescence

• Kimberly A. Wilson
• Dr. Susan Piepho
• Intermediate Lab 3
• March 7, 2005

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Purpose of the lab

• Explore Emission Spectroscopy
• Fluorescence spectrum
• Decay curve at fixed wavelength
• Fluorescence spectrum while quenching in air
  saturated solutions

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Absorption

• Franck-Condon principle
• Excitation to higher vibrational state from the
  lower vibrational ground state by laser

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Fluorescence

• Undergoes radiationless decay
• Radiative transition (fluorescence)

Singlet (S1)
Singlet (S0)
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Scheme

• So hv1 S Rate I abs
  (excitation)
• S S1 (non radiative decay)
• S1 So hv2 (fluorescence)
• S1 So SS (excimer formation)
• SS So So hv3 (excimer
  fluorescence)

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The Nd YAG laser

• Four level system
• Yttrium Aluminum Garnet (YAG) crystal doped with
  Nd3
• Primary lasing wavelength 266 nm

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The Laser
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Laser Set Up
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Absorption Spectrum of Pyrene
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Fluorescence Spectrum

• Pyrene 10-3M
• De-oxygenated with argon
• Delay 0
• Gate Width 90ns

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Fluorescence Spectrum

• Pyrene 10-3M
• De-oxygenated
• Delay 0
• Gate Width 2ns

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Fluorescence Spectrum

• Pyrene 10-3M
• De-oxygenated
• Delay 0
• Gate Width 2ns positioned at 60ns

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Fluorescence Spectrum

• Pyrene 10-4M
• Delay 0
• Gate Width 3 ns
• Air saturated solution

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Decay Curve

• Pyrene 10-4M
• Air saturated solution
• Monochrometer set at 376nm

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Decay Curve

• Pyrene 10-4M
• De-oxygenated solution
• Monochrometer set at 376 nm

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Decay Curve

• Pyrene 10-3M
• De-oxygenated
• Monochrometer set at 376nm

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Decay Curve

• Pyrene 10-3M
• De-oxygenated
• Monochrometer set at 480nm

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Table of Estimated Lifetimes
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Importance

• Able to achieve same results as Van Dyke et al.
• Determine lifetime
• Record fluorescence spectrum

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Questions?
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Decay Curves
t

• Lifetime 1/kobs is the time t that it
  takes for I(t) to fall to 1/e its initial value
  or I 0.37 Io.

t
t
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Absorption Spectrum of Anthracene
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Fluorescence Spectrum

• Anthracene
• Air Saturated Solution
• Gate Width 3ns
• Delay 0

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Decay Curve

• Anthracene
• Air Saturated Solution
• Monochrometer set at 404nm