Presentation is loading. Please wait.

Presentation is loading. Please wait.

NUCLEAR STRUCTURE PHENOMENOLOGICAL MODELS

Similar presentations


Presentation on theme: "NUCLEAR STRUCTURE PHENOMENOLOGICAL MODELS"— Presentation transcript:

1 NUCLEAR STRUCTURE PHENOMENOLOGICAL MODELS
From molecules to atomic nuclei. Standard model Basic concepts of nuclear physics. Units Properties of nucleons Liquid drop model Surface vibration and rotation MICROSCOPIC MODELS Nuclear force Nuclear mean field Shell model Second quantisation in the mean field Residual interaction. Collective excitations Collective model. Nilsson model

2 From molecules to atomic nuclei
10-15m=1fm

3

4 Standard model

5 Basic concepts of nuclear physics
nucleon: proton or neutron nuclide: nucleus uniquely specified by number of protons (Z) and neutrons (N) mass number: A=Z+N isotopes: nuclides with the same Z ex: 235U and 238U isotones: nuclides with the same N ex: 2H, 3He isobars: nuclides with the same A atomic mass unit: 1u=1/12 m(12C) = kg=931.5 MeV/c2

6 Basic physical observables in nuclei
Electric quadrupole momentum Angular momentum Magnetic dipole momentum Parity Energy levels Decay rates

7 Electric quadrupole moment

8

9

10 Magnetic dipole moment

11

12

13 Units used in nuclear physics
Length 1 fm =10-15 m Energy 1 MeV = 106 eV 1 eV = 1, J Basic constants MN=938,90 MeV/c2 ħc=197,33 MeV fm e2=ħc/137=1,44 MeV fm

14 Properties of nucleons
proton neutron mass = MeV/c2 = MeV/c2 charge +1 spin 1/2 magnetic moment μN μN parity

15 Nuclear chart stability of nuclei

16 Limits of stable nuclei exotic nuclei

17 Nuclear size from electron scattering experiments

18 Binding energy Mass defect

19 Example

20

21 Binding energy/nucleon: B/A

22 Liquid drop model Weizsäcker semiempirical formula (1935)

23

24

25 Symmetry energy

26

27

28 Liquid drop energy versus (Z,N)

29 Surface vibration and rotation Deformation parameters of the nuclear surface

30

31 Vibrational states

32 Rotational states

33

34 Total spin I and its projections to laboratory (M) and intrinsic (K) systems
Ω

35 Parameters in the intrinsic system
Ω is the rotation angle

36 β & γ vibrations of a deformed shape

37 Rotational-vibrational model Rotational bands
built on top of the vibrational band head

38 Sakai-Sheline rule vibrational states → rotational bands

39 Nuclear force

40 Deuteron: the simplest nuclear system

41 Deuteron spin & magnetic moment

42

43

44

45

46

47

48

49

50

51

52 Electromagnetic versus strong field

53 Yukawa potential

54 Shell model

55 Nuclear mean field: the selfconsistent single particle potential created by all nucleons

56 Mean field potential for protons and neutrons

57 Spin-orbit interaction

58 Example

59 Shell model magic numbers appear due to the spin-orbit interaction

60 Spherical shell model scheme

61 The last nucleon of an odd-even (even-odd) nucleus determines the nuclear properties (spin, quadrupole and magnetic moments)

62

63

64 Schmidt limits for magnetic moments

65

66 Schmidt limits for quadupole moments

67 creation/annihilation
Second quantisation in the mean field Each spherical level is filled by 2j+1 nucleons with different projections creation/annihilation operators for nucleons (fermions) Fermi level Ground state is a Slater determinant obeying the Pauli exclusion principle

68 Particle (croses) and hole (open circles) states
p-h excitation:

69 (p,2p) reaction in the shell model

70

71 Residual interaction among nucleons in the mean field
Multipole expansion l=0 : pairing l=2 : quadrupole-quadrupole

72 Quasiparticle Hamiltonian approximation Ground state =BCS vacuum
Particle-particle (p-p) short-range interaction describes pairing correlations Quasiparticle approximation Hamiltonian Ground state =BCS vacuum

73 Occupation probabilities Gap parameter
Normal system Superfluid system Fermi level

74 Proton gap versus Z

75 Particle-hole (p-h) long-range interaction describes collective excitations: 1) low-lying surface vibrations 2) giant resonance of protons against neutrons Hamiltonian p-h excitation p h

76 Distribution of collective excitations for various multipolarities versus energy
Giant resonance Low-lying vibrational state

77 Collective model

78 Nilsson model of single particle states in the deformed intrinsic system
Single particle energy versus deformation Deformed Hamiltonian

79 DECAY PROCESSES Alpha decay, cluster emission Beta decay Gamma decay
Fission and fusion

80 Nuclear decay modes

81 Decay law Decay width Γ=ħλ

82 Narrow decaying resonance (Γ is small) is a quasi-stationary process

83 Decay rate (activity)

84

85 Alpha decay

86

87 The first probabilistic interpretation
G. Gamow "Zur Quantentheorie des Atomkernes" (On the quantum theory of the atomic nucleus), Zeitschrift für Physik, vol. 51, (1928). The first probabilistic interpretation of the wave function Rext Internal region External region

88 Quantum penetration explains Geiger-Nuttall law for α and cluster decays (C, O, Ne, Mg, Si)
Coulomb parameter

89 Beta decay

90

91

92

93 Fermi & Gamow-Teller transitions

94

95 Gamma decay

96 Parity rules for gamma transitions

97 Decay operators in second quantisation: gamma transitions beta transitions

98 Fission & fusion

99 Fission - liquid drop model

100 Energy release for various processes

101 Strutinsky shell-model correction The double humped barrier determines the occurrence of superhevy nuclei Density of levels liquid drop shell model

102 Superheavy nuclei are formed by fusion and detected by alpha decay chains

103 Fusion energy

104 The Sun


Download ppt "NUCLEAR STRUCTURE PHENOMENOLOGICAL MODELS"

Similar presentations


Ads by Google