Nuclear physics: the ISOLDE facility. Lecture 1: Nuclear physics . Magdalena Kowalska CERN, PHDept. [email protected] on behalf of the CERN ISOLDE team www.cern.ch/isolde. Outline . Aimed at both physics and nonphysics students. This lecture: Introduction to nuclear physics
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Lecture 1: Nuclear physics
Magdalena Kowalska
CERN, PHDept.
on behalf of the CERN ISOLDE team
www.cern.ch/isolde
Aimed at both physics and nonphysics students
Matter
Crystal
Atom
Atomic
nucleus
Macroscopic
Nucleon
Quark
Nuclear physics:
studies the properties of nuclei and
the interactions inside and between them
Today: the exact form of the nuclear interaction is still not known, but we are getting to know it better and better with many dedicated facilities
Known nuclides
A
X
Z
N
Isomers = longlived nuclear excited states
e
n
p
ν

Nuclear potential
+/EC decay
decay
p decay
spontaneous fission
Proton dripline
neutron dripline
protons
Magic numbers
neutrons
 About 300 stable isotopes: nuclear models developed for these systems
 3000 radioactive isotopes discovered up to now (many of them made only in labs)
 Over 7000 nuclei predicted to exist
b
n
b+,e
p
a
neutrons
a particle in a nucleus
Tunneling
Gamma ray relative intensities and energies (in keV)
Charge distribution
radius of nucleus (fm)
R = 1.25 x A1/3 (fm)
A1/3
M(N,Z) = N Mn + Z Mp –B(N,Z)
fission
Direction of energy release
fusion
Examples of halflives:
11Li: 9 ms
13Be: 0.5 ns
77Ge: 11h
173Lu: 74 us
208Pb: stable
protons
neutrons
Nucleus = N nucleons in strong interaction
The manybody problem
(the behavior of each nucleon
influences the others)
NucleonNucleon force
unknown
No complete derivation from the QCD
Can be solved exactly for N < 10
For N > 10 : approximations
Different forces used depending
on the method chosen to solve the
manybody problem
Additional terms > shell model
First ionization energy in atoms
Challenge: created for stable nuclei,
is it valid for radionuclides?
Differences to atomic shell model
2 kinds of interacting fermions
Observables:
Groundstate properties: mass, radius, moments
Halflives and decay modes
Transition probabilities
Main models:
Shell model (magic numbers)
Meanfield models (deformations)
Abinitio approaches (light nuclei)
(NuPECC longrange plan 2010)
Atoms
Nuclei
shell model: e fill quantized energy levels
shell model (but not only): p and n separately fill quantized energy levels
Description
n, l, ml, s, parity (1)l
n, l, ml, s, parity (1)l
Quantum numbers
max. S possible
(due to Coulomb force):
J= L+S=Sli + Ssi or J= Sji = S(li +si)
min. S possible
(due to strong force pairing):
J = Sji = S(li +si)
Lowest en. levels
Spinorbit coupling
weak
strong
for 3 electrons in a d orbital
for 3 nucleons
in a d orbital
d3/2
d5/2
calculated by solving Schrödinger equation with central potential dominated by nuclear Coulomb field
Energy levels
not easily calculated; nucleons move and interact within a selfcreated potential
After http://webdocs.gsi.de/~wolle/TELEKOLLEG/KERN/LECTURE/Fraser/L5.pdf
If nuclear force is charge independent, why does system with 1n and 1p exist (deuteron), but that with 2n and 2p, etc don’t? And what binds neutrons in neutron stars?
bound
unbound
Not allowed
n
p
n
p
n
p
p
n
p
n
n
p
↑
↑
↑
↓
↓
↓
↑
↑
↑
↑
↑
↑
See more details in http://webdocs.gsi.de/~wolle/TELEKOLLEG/KERN/LECTURE/Fraser/L5.pdf
http://www.nscl.msu.edu/~thoennes/isotopes/criteria.html
Aoki, Ishii, Matsuda
=> Nuclear models have problems predicting and even explaining the observations
11Li:3p,8n
discussed
208Pb:82p,126n
11
8
11
8
8
Halo: nucleus built from a core and at least one neutron/proton with spatial distribution much larger than that of the core
1985: first halo system identified: 11Li
2013: halfdozen other halos known
Nuclear structure and corehalo interaction still not well understood
=> Crucial information:
Mass/binding energy
Spinparity
Magnetic moment
Mass and charge radius
Quadrupole moment
Energy level scheme
Recent achievements: charge radii of 11Li (Uni Mainz/GSI), 6He (Argonne)