Silicon, Circuits, and the Digital Revolution

Excited States

• State of equilibrium, state of lowest energy, is known as the ground state
• Higher energy states are known as excited states.
  • with orbitals that are larger, with different shapes.
• Electrons can be promoted to higher orbits by:
  • collisions with other atoms
  • bombardment with electrons or other particles
  • absorption of light...
• Light is emitted when atom relaxes to ground state from excited state.
  • Light is electromagnetic radiation
  • "pure" energy -- photons
  • The electromagnetic spectrum
  • The visible spectrum
• Demonstrations of discharge lamp (with neon, hydrogen, and oxygen), falling kg mass

Quantum Leaps

• On careful examination, we find that light emitted by excited atoms has discrete values of energy.
• Deduce that electrons in an atom have discrete values of energy.
• Energy levels of electrons in an atom are quantized.
  • Energy level diagrams -- sample of emission spectrum: hydrogen
  • Quantum physics

Additional Online References

Visual Quantum Mechanics -- Laser Adventure from Physics Education Group at Kansas State Univ.

Bohr Model of the Atom

Energy States (Levels)

Photons and the Energy Diagrams

Spontaneous Emission of Electromagnetic Radiation

Comments, suggestions, or requests to ghw@udel.edu. "http://www.physics.udel.edu/~watson/scen103/colloq2000/excitedstates.html" Last updated April 17, 2000. © George Watson, Univ. of Delaware, 2000.