Transcript chapter1_091407

“And on the seventh day God finished His work
which He had done, and He rested on the seventh day
from all His work which He had done.”
(Genesis 2:2)
Chapter 1
INTRODUCTION
1.1
Historical perspective
1.2
The Rutherford scattering formula
1.3
The properties of the Rutherford differential cross-section
1.4
The experiments of Rutherford and his colleagues
1.5
Examination of the assumptions
1.6
The nuclear constituents
1.7
What is coming?
§ 1.1 Historical perspective
1895
1896
The discovery of X-rays
Discovery of radioactivity
Röntgen
Becquerel
4
U 234
Th

90
2 He
238
92
1897
1900
1905
1911
1912
1913
1919
1920
The discovery of electron
The discovery of the black body radiation formula
The development of the theory of special relativity
Rutherford’s atomic model
Discovery of isotopes
Bohr’s theory of the hydrogen atom
Induced nuclear transmutation
The radii of a few heavy nuclei
~ 10-14 m = 10 F << 10-10 m
J.J. Thomson
Max Planck
Albert Einstein
Rutherford
J.J. Thomson
Niels Bohr
J.J. Thomson
Chadwick
1928 Alpha decay
1932 Discovery of neutron
1932 n-p hypothesis
1932 Discovery of positron
1934 Beta decay
1935 Roles of mesons in nuclear forces
1936 Discovery of μ meson
1946 Discovery of π meson
1956 Non-conservation of parity in beta decay
Gamow, Gurney and Condon
Chadwick
Heisenberg
Anderson
Enrico Fermi
Yukawa
Anderson and Neddermeyer
Powell
Lee, Yang and 吳健雄教授
Atomic Physics
The physics of the electronic, extra-nuclear structure of
atoms
Nuclear Physics
The physics of the atomic nucleus, believed to be constituted
of neutrons and protons
Elementary Particle Physics
The physics of quarks and gluons, believed to be the
constituents of protons and neutrons, and of leptons
and gauge bosons and…
who knows what else!
Quarks, gluons, leptons, and gauge bosons are believed to
have no substructure.
SIMPLE NUCLEI
Most visible mass in the universe is in the form of atomic nuclei
Hydrogen
About 75% protons
The rest mainly helium
Deuterium
For every proton there are about 108 photons
Universe is essentially space and nuclei
Dark Energy and Dark Matter!
Helium
Big Bang !!
The universe is expanding
→ BIG BANG model
a quick history
(0) at the end of the first
nanosecond (10-9 s) matter
consisted of quarks,
leptons
and the various bosons
which
transmit the forces between
them
The fundamental particles
The fundamental particles
History of Nuclei
(1) As the universe expanded from very high density, pressure and temperature
it cooled allowing the strong force between the quarks (anti-quarks) to bind
them together into particles called hadrons (baryons or mesons).
(2) With further expansion the hadrons separated from each other, decays
occurred and only the most stable species survived. At the end of the first
microsecond the only hadrons remaining were protons and neutrons together
with electrons (positrons), their neutrinos (antineutrinos) and photons.
History of Nuclei
(3) Up to first second the universe continued to expand and cool - radioactive decay
and its inverse ensuring equilibrium between the numbers of protons and neutrons.
(4) Up to the first fifteen minutes the temperature cooled sufficiently that neutrons
and protons could bind together to form deuterons (one proton and one neutron) and
the more tightly bound alpha particle (two protons and two neutrons). This was the
epoch of primordial nucleosynthesis
(5) For the next million years or so the universe was an expanding and slowly
cooling mixture of nuclei, electrons, neutrinos and photons.
History of Nuclei
(6) By the time the universe was a thousand million years old, atoms and
molecules had clustered together in large clouds which were further squeezed
into stars by mutual gravitational attraction.
(7) The collapse is halted and the star is fuelled by the process of nuclear fusion
which converts hydrogen into helium and then into heavier nuclei. Thus a second
phase of the production of nuclei occurred - so called stellar nucleosynthesis.
There are three types of radiations:
1. α-rays:
These were found to be positively charged particles with a ratio of
charge to mass about one half that of a singly charged hydrogen atom.
It became clear afterward that these rays were energetic nuclei of
helium.
2. β-rays:
These are negatively charged particles which were found to be
identical to the electrons found by J. J. Thomson.
3. γ-rays:
These are electrically neutral particles with properties which
identified them as energetic photons.