atomic physics micro-world macro-world lecture 15 dimitri mendeleev
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Atomic Physics
Micro-world Macro-world
Lecture 15
Dimitri Mendeleev
Periodic table of elementsElements in vertical rows have similar
chemical properties
Inert
gases
Schroedinger’s Equation for multi-electron Atoms
-
-
-
--+
Solutions give energy levels that are clustered in “shells”
+-
--
--
-
--
--
-
-
- -
-
-
--
n # of states
1 2
2 8
3a 8
3b 10
4a 84b 104c 14
Pauli exclusion principle
Only one electron per quantum state
Once a quantum state is occupiedadditional electrons are excluded
WolfgangPauli
Light elements
+1
-
+2-
-Hydrogen Helium
+3-
-
Lithium
-+10-
--
--
-
--
--
Neon
1 electron inoutermost shell
outermost shell is full
Periodic table of elementsElements in vertical rows have similar
chemical properties
1 e
- in
ou
ter
sh
ell
Fille
d o
ute
r sh
ell
Chemical properties depend upon the outermost shell configuration
+8-
---
-
--
-
Oxygen
+16-
---
-
-
--
--
-
-
-
---SulfurOutermost shells
Have 2 vacancies
Periodic table of elements
2 v
acan
cie
s in
ou
ter
sh
ell
Atoms combine to form molecules by filling outer shells
+8-
---
-
--
-
Oxygen+1-
Hydrogen
+1
-Hydrogen
Water=H2O
Atoms combine to form molecules by filling outer shells
+6-
---
-
-
Carbon+1-
Hydrogen
+1
-
Hydrogen
Methane=CH4
+1-
Hydrogen
+1-
Hydrogen
Elements with full outer shells don’t form molecules
+2-
-Helium
+10---
--
-
--
--
Neon
+18-
--
--
-
-
--
-
-
-
- --
---
ArgonNoble gasses
Periodic table revisited
Elements in vertical rows have sameouter shell configurations
Ou
ter
sh
ell is f
ull
1 e
lec in
ou
ter
sh
ell
2 v
acan
cie
s in
ou
ter
sh
ell
4 e
- in
ou
ter
sh
ell
Quantum theory & Atomic spectra
Spectra are atomic “signatures”
Hydrogen
Mercury
Neon
Mercuryspectrum
“quantum jump”
quantum orbits
Mercury energy levels
qu
an
tum
en
erg
ies
Decoding atomic spectra
photon
Ephoton=E2-E1
1924 Otto Laporte
even
even
even
even
od
d
od
d
od
d
od
d
odd even
oddeven
odd
even
odd
even XX
Otto Laporte1902-1971
Allowed quantum states are either even or odd
Laport rule
OK
notallowed
Laporte rule is a consequence ofLeft-Right symmetry of Nature
Left Right symmetry= “Parity” symmetryEugene Wigner
1902-1995Eugene Wigner1902-1995
1963 Nobel Physics prize “for the discovery and applicationof fundamental symmetry principles”
P = Parity = L R/R L
Field (& rules) of footballare parity symmetric
Rules of baseball arenot parity symmetric
Even & Odd quantum functions
LR RL LR RL
Even Function Odd Function
Does not change Changes signParity = +1 Parity = -1
Parity Conservation in QM
Left Right symmetry of Nature
Conservation of Parity
even state
odd state
photonhas P=-
1 initially:
even state(Peven=+1)
Photon
(Pphot=-1)
Pinitial=+1 Pfinal=(-1)(-1)=+1
Parity is conserved
finally:
odd state+ (Podd=-1)
Atomic red shifts
V=0.01c=3,000km/s shift = 1%
V=0.05c=15,000km/s shift= 5%
V=0.25c=75,000km/sshift = 25%
Laser
Example: Helium-Neon Laser Cartoon:
– Light Amplification by Stimulated Emission of Radiation –
Helium-Neon gas mixture
sealed container
+ -
I I I
mirror
“partial”mirror
Power source
Helium-Neon Laser in real life
Laser
→ →
→Exactly in phase
→
→
→
→Exactly in phase
Ne*
Ne*
Ne*
Ne*
Ne*
Ne*
→
→
→
→
Exactly in phase
→
→
→→Stimulates
emission
– Light Amplification by Stimulated Emission of Radiation –
“meta-stable” states
“Pump”