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Quantum Phenomena II: Revision

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Integer in range 0 to n-1. m (or ml ) fixes z component of angular momentum ... Where g is gyromagnetic ratio ~ 2] 5. Energy Levels cont.. For multi-electron atoms ... – PowerPoint PPT presentation

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Title: Quantum Phenomena II: Revision


1
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
2
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

3
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

4
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

5
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

6
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.

7
Particle interactions
  • Some basic standard model vertices

8
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
9
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
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