Section 1
Questions
Was there a stage in the development of atomic physics in which models played a role comparable to that now played by models in nuclear physics? Are models used now in atomic physics?
In those regions of the universe where thermal energy is $k T \sim 10^{6} \mathrm{eV}$, are atomic processes more apparent than nuclear processes? What about those regions where $k T \sim$ $10^{-6} \mathrm{eV} ?$
Is a positive electric point charge surrounded by a concentric circular ring of negative charge, of total magnitude equal to that of the point charge, an electric monopole, dipole, quadrupole, or something else?
All nuclei have an electric monopole moment (which measures their total charge). Some nuclei have an electric quadrupole moment (which measures the departure from a spherical shape of their charge distribution). No nuclei have an electric dipole moment (which would measure the departure of the center of their charge distribution from the center of their mass distribution). Why would we not expect electric dipole moments for nuclei?
Nuclei have magnetic dipole moments. Why do they not have magnetic monopole moments? What about magnetic quadrupole moments?
If an electron of kinetic energy $100 \mathrm{keV}$ passed through a typical atom it could be scattered through a fairly large angle in a close collision with an atomic electron. If its kinetic energy is $100 \mathrm{MeV}$ it could be scattered through a fairly large angle only in a close collision with the nucleus. Why?
Why is the mass unit not defined in terms of the mass of the hydrogen atom? (Hint: Use Table $15-1$ to make a quick estimate of the mass of ${ }^{92} \mathrm{U}^{238}$ if the mass of ${ }^{1} \mathrm{H}^{1}$ is $1.000000 u .)$
Since atomic and molecular reactions also involve binding energics, why did the nineteenth century chemists not obsetve mass deficiencies and thereby discover relativity theory?
Many textbook problems in mechanics consider zero $Q$-value collisions between idealized classical particles. Is the $Q$ value exactly zero in collisions between real classical particles (like real billiard balls)? What is the sign of the $Q$ value?
Why are the most stable nuclei found in the region near $A \simeq 60 ?$ Why do not all nuclei have $A \simeq 60 ?$
The semiempirical mass formula contains five parameters, and it predicts quite accurately more than 500 masses. How does its ratio of predictions to parameters compare with other empirical formulas of physics or engineering?
Why does the pairing term make a negative contribution to the energy liberated when a neutron is captured by ${ }^{92} \mathrm{U}^{238}$, and a positive contribution in the case of ${ }^{92} \mathrm{U}^{235} ?$ What are the practical consequences of this situation?
$$\text { Why are the atomic magic numbers not the same as the nuclear magic numbers? }$$
Explain why there can be no collisions between a typical nucleon and another in a nucleus in its ground state. If a high-energy nucleon, say from a cyclotron beam, enters a nucleus in its ground state, can it collide with a nucleon in the nucleus?
What fundamental law of physics is most responsible for the existence of nuclear magic numbers?
Is there a relation between the $l$ dependence of the spin-orbit splitting of nuclear levels. and the Landé interval rule for the spin-orbit splitting of atomic energy levels?
$$\text { Why do most nuclei obey } J J \text { coupling, whereas most atoms obey } L S \text { coupling? }$$
Use the argument associated with Figure $9-4$ to explain why there is a tendency for the intrinsic spin angular momenta of a pair of identical nucleons to be essentially antiparallel in order to minimize their average separation. Then modify the argument illustrated in Figure $10-2$ to explain why the average separation of the pair is minimized if their orbital angular momenta are also essentially antiparallel. Do these arguments explain why the pairing interaction tends to make the total angular momenta of the pair essentially antiparallel?
If one factor in a nuclear cigenfunction consists of a product of an cven number of eigenfunctions for nucleons in a particular subshell, why is the parity of the factor even, independent of whether the paritics of the nucleon eigenfunctions are all even or all odd? How does this lead to the rule for predicting the parities of odd- $A$ nuclear eigenfunctions?
How can the magnetic dipole moment data of Figure $15-19$ be used to identify the orbital angular momentum quantum number $l$, of many nuclei, in terms of the measured value of their total angular momentum quantum number $j$ ?
If the tidal waves circulating around the nuclear core in the collective model were entirely composed of protons, instead of being composed partly of protons and partly of neutrons, what would be the effect on the magnetic dipole moments predicted by the model?
What is the simplest distribution of point charges that has an electric quadrupole moment?
Why are there no magic numbers that are odd?
Why is the nuclear shell model called a model, while the comparable atomic Hartree theory is called a theory? Generally speaking, how does a model differ from a theory?