Quantum Phenomena II: Revision

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Quantum Phenomena IIRevision
Fundamental Physics
Atomic Structure

• Hydrogen atom
• Quantum numbers
• Electron intrinsic spin
• Other atoms
• More electrons!
• Pauli Exclusion Principle
• Periodic Table

• Particle Physics
• The fundamental particles
• The fundamental forces
• Cosmology
• The big bang
• The evolution of the universe

http//ppewww.ph.gla.ac.uk/parkes/teaching/QP/QP.
html
Chris Parkes
April/May 2003
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Quantum Numbers

• Atom can only be in a discrete set of states
  n,l,m
• Diff. From classical picture with any orbit
• Principle n fixes energy - quantized
• Integer gt1
• l fixes angular momentum L
• Integer in range 0 to n-1
• m (or ml ) fixes z component of angular momentum
• Integer in range l to l

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Total Angular momentum

• Orbital angular momentum L, e orbiting nucleus
• L2l(l1)h
• Quantum number l
• notation lspdfg., l0,1,2,3,4
• l has z-component ml, (-l.l)
• Interacts with magnetic field, Uml?BB
• Zeeman effect gives splitting of states
• Spin s1/2, intrinsic property of electron
• Has ms -1/2, 1/2
• So splits an l state into two
• Total Angular Momentum J
• Sum of orbital and spin
• Anomalous Zeeman effect / Stern-Gerlach Expt

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Energy levels

• Hydrogen Energy levels ? 1/n2 , scale is eV
• In a magnetic field E will depend upon other
  quantum numbers (ml,ms), for Zeeman effect this
  is
• For anomalous zeeman effect from electron spin
  it is
• Where g is gyromagnetic ratio 2

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Energy Levels cont..

• For multi-electron atoms
• Energy splitting depends on l even in absence of
  magnetic field.
• occurs due to screening effect
• Central field approximation
• Pauli Exclusion principle
• No two fermions in same state
• Structure of Periodic table

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Particle Physics

• Forces are due to exchange of the fundamental
  force carrying bosons
• Photon,gluon,W,W-,Zo (and presumably graviton)
• Know the fundamental particles
• Three generations of quarks and leptons
• Dont observe free quarks
• Confined in colourless hadrons
• Added some more conservation laws
• Energy, momentum, electric charge
• Baryon number, lepton number
• Particle interactions can be written as Feynman
  diagrams
• Know the basic vertices, and conservation laws to
  see whether or not a reaction will occur.

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Particle interactions

• Some basic standard model vertices

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The Big Bang

• Evidence for the Big Bang
• It is dark at night! See Olbers Paradox
• Universe expanding
• Cosmic microwave background
• Relative abundance of elements in universe
• Universe Expanding Hubbles law
• Hence universe 15 billion years old

v H x d, Velocity Hubble const.
distance
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Evolution of the universe

• Controlled by Quantum Phenomena
• Early stages dominated by basic particle physics
• Later stages by gravitational effects
• Starts at high temp., high density
• Cools down and expands.
• Key stages
• Separation of forces into the four basic forces
• Formation of nuclei
• Formation of atoms
• Microwave background radiation, remnant photons
  from when atoms formed
• Then gravitation dominates and stars and galaxies
  form