Part 1

Question 1

Strong force

Answer 1

Nucleus loses material (alpha-decay, fission)

Question 2

Weak force

Answer 2

Changes proton/neutrino ratio (beta-decay)

Question 3

EM force

Answer 3

De-excitation by gamma-ray emission

Question 4

Alpha decay

Answer 4

Heavy nuclei

Question 5

Beta decay

Answer 5

All nuclei at each side of stability valley

Question 6

Gamma decay

Answer 6

All nuclei in excited states

Question 7

Proton emission

Answer 7

Few nuclei along proton drip line

Question 8

Spontaneous fission

Answer 8

Mass, A>230

Question 9

Spin-orbit coupling

Answer 9

LS-coupling arises from term in the nuclear potential. V(r) = V(r)_ws + W(r)LdotS. Causes splitting of levels and energy shift proportional to j(j+1) - l(l+1) - s(s+1). (With s=1/2)

Question 10

Nuclear shell structure

Answer 10

Each nuclear state has intrinsic spin J and parity pi. Protons and neutrons pair up, every pair has parity, pi=1.

Question 11

Even-even Nuclei

Answer 11

0+

Question 12

Odd A Nuclei

Answer 12

Have one unpaired nucleon. The spin of the nucleus is equal to that of the unpaired nucleon. Parity=(-1)^l where l is the orbital angular momentum of the unpaired nucleon.

Question 13

Odd-odd Nuclei

Answer 13

Unpaired proton with j_p and an unpaired neutron with j_n. Total spin of the nucleus is the vector sum of the two values and can take values between |j_p – j_n| and |j_p + j_n| in unit steps. Parity is given by (-1)^(l_p+l_n), where l_p and l_n are orbital angular momenta of the unpaired proton and neutron.

Question 14

Fermi-Kurie plot

Answer 14

Can be calculated from beta spectra. Allows us to determine if an observed transition is allowed vs forbidden, and allows better determination of the end point energy. Straight line means no orbital angular momentum – pure fermi decay.

Question 15

FT value

Answer 15

Comparative half-life. Correlation between Log(ft) and type of transition. The lowest permitted order of ‘forbiddeness’ will dominate the transition.

Question 16

Three types of gamma-decay excited states

Answer 16

Single nucleon excitation states.
Vibrational excited states.
Rotational excited states.

Question 17

Gamma decay: Single nucleon excitation states

Answer 17

Best for lowest-lying excitations of oddA nuclei near closed shells.
A low-lying states: last particle (valence nucleon) is excited to the next shell.
Higher energy states: braking a pair at a lower configuration in the shell structure.

Question 18

Gamma decay: Vibrational excitation states

Answer 18

Occur when a nucleus oscillates about a spherical equilibrium shape. Form of the excitations can be represented by a multipole expansion.