# the semi-empirical mass formula

Post on 31-Dec-2015

290 views

Category:

## Documents

Tags:

• #### stabilitynuclear spin

Embed Size (px)

DESCRIPTION

The Semi-empirical Mass Formula. Variations……. Additional physics…. Fitting……(Global vs. local)…. Quiz. Mass Parabolas and Stability. HW 15. Mass Parabolas and Stability. Mass Parabolas and Stability. Mass Parabolas and Stability. Mass Parabolas and Stability. - PowerPoint PPT Presentation

TRANSCRIPT

• The Semi-empirical Mass FormulaVariations.Additional physics.Fitting(Global vs. local)..

• Quiz

• Mass Parabolas and StabilityHW 15

• Mass Parabolas and Stability

• Mass Parabolas and Stability

• Mass Parabolas and Stability

• Mass Parabolas and StabilityOdd-OddEven-EvenVertical spacing between both parabolas ?

Determine constants from atomic masses.

• Mass Parabolas and Stability

• Nuclear Spin Neutrons and protons have s = (ms = ) so they are fermions and obey the Pauli-Exclusion Principle.The Pauli-Exclusion Principle applies to neutrons and protons separately (distinguishable from each other) (Isospin). Nucleus seen as single entity with intrinsic angular momentum . Associated with each nuclear spin is a nuclear magnetic moment which produces magnetic interactions with its environment. The suggestion that the angular momenta of nucleons tend to form pairs is supported by the fact that all nuclei with even Z and even N have nuclear spin =0. Iron isotopes (even-Z), for even-N (even-A) nuclei =0. Odd-A contribution of odd neutron half-integer spin. Cobalt (odd-Z), for even-N contribution of odd proton half-integer spin. Odd-N two unpaired nucleons large integer spin.

• Nuclear Spin

• Nuclear Spin

• Nuclear Magnetic MomentRemember, for electronsRevise: Torque on a current loop.Z component ?? Experiment, applied magnetic field.Gyromagnetic ratio (g-factor)

• Nuclear Magnetic MomentFor NucleiFor free protons and neutronsProton: g = 5.5856912 0.0000022 3.6 Neutron: g = -3.8260837 0.0000018 3.8

The proton g-factor is far from the gS = 2 for the electron, and even the uncharged neutron has a sizable magnetic moment!!! Internal structure (quarks).

• Nuclear Magnetic Moment

• Nuclear Parity (r) (-r) Even. (r) -(-r) odd. For a nucleon is either of even ( = +) or odd ( = -) parity. For the nucleus = 1 2 3 A. Practically not possible. Overall can be determined experimentally. Overall for a nucleus (nuclear state). Transitions and multipolarity of transitions (-emission).