Atomic Structure Lecture Outline

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Fred J. Grieman
Atomic Structure (Lecture Outline) Classical
world of particles and waves Classical failures
blackbody radiation and
photoelectric effect Particle/wave
duality interference Setting up atomic physics
wavefunctions
probabilities
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Classical Picture of the World
Rutherford Planetary atom nucleus (p,n)
charge Z, most of mass electrons surrounding
nucleus Classical View Matter particles
(lumps) of mass m (we will often idealize
as localized points) E EK EP ½mv2 EP
no restriction on E p2/2m EP p
mv momentum Particle encounter collide and
exchange energy Light waves (delocalized)
Electromagnetic
oscillating electric magnetic
fields.
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A f(r,t) Instant in time A f(r) A0cos
(2p r/?) mathematical function for wave
?(distance) wavelength Fixed position A
f(t) A0cos (2p t ?) ?(time-1)
frequency Speed of wave (distance/time) ?(distan
ce) ?(time-1) speed of light
c c0 (vacuum)
t
r
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2) Two Slit Experiment
http//vsg.quasihome.com/interfer.htm
Determining wavelength (?) from diffraction
pattern
From spacing of peaks, D h can
determine wavelength (?) of monochroma- tic light
source
Light wave encounter Interference
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- -
- -
- -
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Classical Failure Blackbody Radiation Planck
emit
Model Vibrating oscillators that
absorb and emit energy
Perfect body only absorb At some Temp. T
Classical High energy (short ?) oscillators
Lots of them, can continually
absorb low energy and then
emit
Continually absorb energy and then emit
E
Leads to infinite energy Impossible!!!
Planck Quantum Hypothesis Oscillators cant
absorb continuously Rather absorb in chunks of
energy called quanta h? Where h is Plancks
constant h 6.626 x 10-34 Joule seconds
Important result matter absorbs emits energy
in quanta Energy is restricted!
Gives experimental result
E
x
?Eh?
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Another Classical Failure Photoelectric Effect
Einstein
Metals absorb light energy. If enough energy,
emits an electron with Ek Classical Light of
any E(?) metal continuously
absorbs until enough to emit electron
? of electrons and their energy only
depends on intensity of light
e-
E
? work function
Doesnt happen this way! E(light) ? ? for e- to
be emitted Einstein Light as a particle comes
as a quantum Use Planck E(light) h? (depends
on frequency)
Light energy comes in quanta E h? Light as a
particle
E
h?o ? e-s, Ek 0
h? gt ? e-s, Ek (h? - ?)
h? lt ? no e-s
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Whats going on??? Light acting as
particles Particles having only fixed
energy Thought experiment
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X-ray
Electrons!!!
Particles behave as Waves with de
Broglie Wavelength Next time Wave equation
for Particles!
Neutrons!!!
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