2. Presented To : Dr Naveed Ahmad
Presented by : Shahbaz Ali
Class: Msc phy 3rd (eve)
Subject : Nuclear physics l
Roll No :. Mcs2200102
Topic : Collective Model
3. Collective Model
When liquid drop model and shell model fails to explain all
the features of nucleus, Age Bohr, Hill wheeler and James
Rainwater proposed a model called Collective model.
The features of shell model and liquid model are summed up
in this model. The collective model explained the high values
of quadrupole moments.
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According to collective model, the nucleus consists of a hard
core of nucleons (filled-shells) and the outer valence
nucleons behave just like surface molecules in a liquid.
The strong attractive nuclear interaction between core
nucleons and surface valence nucleons will distort the core.
This core will exert a centripetal force on the surface valence
nucleons.
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As a reaction centrifugal force acts on the core which results
into bulges. These bulges circulates around the surface of the
core and results into motion of extra nucleon.
If there are two extra nucleons of the same nucleus,
classically they move in opposite directions around the core
in orbits because their pairing interaction produces anti
parallel coupling of their angular momenta. This increases the
distortion of the core.
