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The measure of things

The measure of things. Periodic system (Mendeleev, 1869). N Avogadro = 6.022 x 10 23 /mole  m H = 1.673 x 10 -24 g. electron shell. nucleus. A = atomic number Z = number of electrons . = number of protons A-Z = number of neutrons. Atomic model Rutherford-Bohr.

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The measure of things

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  1. The measure of things

  2. Periodic system (Mendeleev, 1869) NAvogadro = 6.022 x 10 23 /mole  mH = 1.673 x 10 -24 g

  3. electron shell nucleus A = atomic number Z = number of electrons . = number of protons A-Z = number of neutrons Atomic model Rutherford-Bohr

  4. Discovery of the electron 1896: Zeeman discovers influence of magnetic field on spectral lines e/m 1897: Thomson deflects cathode rays e/m (similar experiments by Kaufmann, Wiechert) 1899: Thomson determines charge e (cloud chamber) electron mass m ≈ 1/2000 mH

  5. Cathode rays Geissler tube Crookes CRT

  6. Deflection of cathode rays by electric fields

  7. Radioactivity: Becquerel (1896) - Discharges an electroscope - M. Curie: atomic property - E. Rutherford (1899): 2 types:  rays (short range)  rays (long range) - M. + P. Curie: e/m  rays are electrons (1900) - E. Rutherford:  rays are 2+ helium ions (1908)

  8. The atomic nucleus Geiger & Marsden (1909-10): scattering of -particles from metal foil (gold, platina) Rutherford (1911): Atoms are almost empty, all mass and positive charge concentrated in a tiny central nucleus

  9. Hydrogen spectrum Balmer (1885): Bohr (1913): quantum theory of spectral lines

  10. Compton effect Elastic scattering of massless photon with electron (initially at rest)  particle nature of photon

  11. Atomic mass M (~ Z) grows faster than atomic number A  not only protons in nucleus Chadwick (1932): neutron  + 9Be  12 C + n

  12. The neutrino -decay of neutron: half-life: 15 min _ n  p + e + e- (Pauli, 1930)

  13. Cosmic rays Theodor Wulf (1909): Spontaneous discharge of electroscope Victor Hess (1911-13): Balloon flights Radiation intensity increases at heights > 4 km

  14. Cosmic ray airshowers (Pierre Auger, 1936)

  15. Anti-matter e- + e+  2  E = me c2 = 0.511 MeV Anderson discovers positive anti-electron (positron) (1932)

  16. New particle families    +  (Powell, 1947) Mass (MeV/c2): 135 - 140 105 495 Pion: (+ , 0 , -) Muon: -, + Kaon: (K+, K0), (K-, K0) _

  17. Hadron spectrum _ _ _ K Spectrum explained by quark structure: p = (uud), n = (udd),  =(ud), K = (us), …

  18. Nucleons Proton Neutron Charge: + e 0 e quarks Charge: + 2/3 e - 1/3 e

  19. Three families: 1897-2000 Particle masses in MeV; 1 MeV  1.81027 gram

  20. Binding forces Electrons: electric Coulomb force (photons) Nucleons: Yukawa forces (pions, not elementary) Quarks: color forces (gluons) e,q , g e,q

  21. Classification of matter particles Charge +2/3, -1/3 0, -1 Quarks: strong interactions, (u, d) Leptons: no strong interactions, (, e) Universality in quark-lepton spectrum: Weak interactions <---> transmutation Charged exchange bosons: W+,W- Neutral exchange boson: Z

  22. Weak vector bosons: W±, Z0 µ µ - u d _ W- e e- µ = 2.2 x 10-6 s in rest frame Note (Einstein): moving clocks go slow t = (v)  ( (v) > 1 )

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