1. Atomic Physics Micro-world Macro-world Lecture 15 Dimitri Mendeleev

2. Periodic table of elements Elements in vertical rows have similar chemical properties Inert gases

3. Schroedinger’s Equation for multi- electron Atoms - - - - - +

4. Solutions give energy levels that are clustered in “shells” + - -- - - - - - - - - - - - - - - - n # of states 1 2 2 8 3a 8 3b 10 4a 8 4b 10 4c 14

5. Pauli exclusion principle Only one electron per quantum state Once a quantum state is occupied additional electrons are excluded Wolfgang Pauli

6. Light elements +1 - +2 - - Hydrogen Helium +3 - - Lithium - +10 - -- - - - - - - - Neon 1 electron in outermost shell outermost shell is full

7. Periodic table of elements Elements in vertical rows have similar chemical properties 1 e - in outer shell Filled outer shell

8. Chemical properties depend upon the outermost shell configuration +8 - -- - - - - - Oxygen +16 - - - - - - - - - - - - - - - - Sulfur Outermost shells Have 2 vacancies

9. Periodic table of elements 2 vacancies in outer shell

10. Atoms combine to form molecules by filling outer shells +8 - -- - - - - - Oxygen +1 - Hydrogen +1 - Hydrogen Water=H 2 O

11. Atoms combine to form molecules by filling outer shells +6 - -- - - - Carbon +1 - Hydrogen +1 - Hydrogen Methane=CH 4 +1 - Hydrogen +1 - Hydrogen

12. Elements with full outer shells don’t form molecules +2 - - Helium +10 - - - - - - - - - - Neon +18 - - - - - - - - - - - - - - - - - - Argon Noble gasses

13. Periodic table revisited Elements in vertical rows have same outer shell configurations Outer shell is full 1 elec in outer shell 2 vacancies in outer shell 4 e - in outer shell

14. Quantum theory & Atomic spectra

15. Spectra are atomic “signatures” Hydrogen Mercury Neon

16. Mercury spectrum “quantum jump” quantum orbits Mercury energy levels quantum energies Decoding atomic spectra photon E photon =E 2 -E 1

17. 1924 Otto Laporte even odd even oddeven odd even odd even X X Otto Laporte 1902-1971 Allowed quantum states are either even or odd Laport rule OK not allowed

18. Laporte rule is a consequence of Left-Right symmetry of Nature Left Right symmetry = “Parity” symmetry Eugene Wigner 1902-1995 Eugene Wigner 1902-1995 1963 Nobel Physics prize “for the discovery and application of fundamental symmetry principles”

19. P = Parity = L R/R L Field (& rules) of football are parity symmetric Rules of baseball are not parity symmetric

20. Even & Odd quantum functions L  R R  L Even Function Odd Function Does not change Changes sign Parity = +1Parity = -1

21. Parity Conservation in QM Left Right symmetry of Nature Conservation of Parity even state odd state photon has P=-1 initially: even state (P even =+1) Photon (P phot =-1) P initial =+1P final =(-1)(-1)=+1 Parity is conserved finally: odd state+ (P odd =-1)

22. Atomic red shifts V=0.01c=3,000km/s shift = 1% V=0.05c=15,000km/s shift= 5% V=0.25c=75,000km/s  shift = 25%

23. Laser Example: Helium-Neon Laser Cartoon: – Light Amplification by Stimulated Emission of Radiation – Helium-Neon gas mixture sealed container +- I II mirror “partial” mirror Power source Helium-Neon Laser in real life

24. Laser → → → Exactly in phase → → → → Ne* → → → → Exactly in phase → → → → Stimulates emission – Light Amplification by Stimulated Emission of Radiation – “meta-stable” states “Pump”