Nuclear Physics

Question 1

beta -

Answer 1

n -> p + e- + v_bar

Question 2

beta +

Answer 2

p -> n + e+ + v

Question 3

electron capture

Answer 3

p + e- -> n + v

Question 4

activity - production + decay

Answer 4

R(1 + e^(-lambda t)), R = N0 sigma I

Question 5

barns to m^2

Answer 5

1b = 10^-28 m^2

Question 6

amu to kg

Answer 6

1 u = 1.66054 x 10^-27

Question 7

average binding energy of a nucleon

Answer 7

8 MeV

Question 8

uncertainty principle

Answer 8

as distribution of momentum increases (lower momentum) distribution of position decrease (is everywhere)

Question 9

what is the range of the nuclear force?

Answer 9

6fm

Question 10

in an incident energy vs xs graph, what do the oscillations mean?

Answer 10

comes from energy being quantized. each spike represents a state. as energy increases there are more states, until there get to be such a dense number that it is represented as a smooth line.

Question 11

What is the peak of the binding energy curve? Where is there a spike?

Answer 11

Iron 56 is the Peak, spike at He4

Question 12

equation for radius of a nuclide

Answer 12

R = R0A^1/3

Question 13

what is the force behind gamma decay?

Answer 13

electromagnetic

Question 14

what’s the force behind beta decay?

Answer 14

the weak force

Question 15

exposure rate

Answer 15

activity/distance^2

Question 16

greys to joules/kg to rad

Answer 16

1 gy = 1 j/kg=100rad

Question 17

what quantities can be related to each other via the uncertainty principle?

Answer 17

momentum and position, energy and time, angular momentum and angle

Question 18

how are energy and cross section related?

Answer 18

as neutron slows down (lower energy) it has a higher cross section

Question 19

When does the wave function look like an exponential decay

Answer 19

when E < U0

Question 20

When does the wave function look oscillatory?

Answer 20

when E > U0

Question 21

can we usually ignore binding energy of the electron?

Answer 21

yes

Question 22

what are some ways you can show a nuclide is unstable using mass data?

Answer 22

Check to see if either type of beta decay is energetically favorable.

Question 23

growth of daughter activities

Answer 23

dN2 = L1N1dt - L2N2dt, N2(t) = N0 L1/(L2 -L1)(e^-L1t - e^-L2t)

Question 24

what assumption about growth of daughter can we make when L1 &laquo_space;L2?

Answer 24

e^-L1t = 1 which gives N2(t) = N0 L1/L2(1 - e^-L2t)

Question 25

what is secular equilibrium?

Answer 25

in a decay chain, as time gets large, nuclei are decaying at the same rate they are being produced.

Question 26

why is alpha decay rare at nuclei of A = 56?

Answer 26

That's the peak of the binding energy curve. Alpha particles are less likely to break off when binding energy is high. You can also calculate Q value there and see that it is not positive.

Question 27

Q for electron capture

Answer 27

Q = [m(x) - m(x')]c^2 - Bn

Question 28

Q for beta -

Answer 28

Q = [m(x) - m(x')]c^2

Question 29

Q for beta +

Answer 29

Q = [m(x) - m(x') - 2m_e]c^2

Question 30

de Broglie wavelength

Answer 30

lambda = h/p, relates wavelength and momentum

Question 31

fermi beta decay

Answer 31

no change in parity or spin.

Question 32

gamow teller

Answer 32

0 or 1 spin change, no parity change

Question 33

first forbidden decay

Answer 33

delta J = 0, 1, 2, delta pi = 1

Question 34

second forbidden decay

Answer 34

delta J = 2, 3, delta pi = 0

Question 35

third forbidden

Answer 35

delta J = 3, 4 delta pi = 1

Question 36

fourth forbidden

Answer 36

delta J = 4, 5 delta pi = 0

Question 37

find allowed multipolarity

Answer 37

every integer in between abs(J_i - J_f) and J_i + J_f, if parity changes must be odd L for electric, even for magnetic. Opposite for no parity change.

Question 38

how does an increase in multipole order correspond to strength?

Answer 38

Increase in multipole order corresponds to a reduction in strength by approximately 10^-5

Question 39

what's the relationship between energy and velocity?

Answer 39

E = (1/2)mv^2

Question 40

conversion between ev and J

Answer 40

1 ev = 1.602189 x 10^-19

Question 41

what force governs alpha decay?

Answer 41

nuclear force and electromagnetic

Question 42

how does alpha decay happen?

Answer 42

Tunneling process. As the width of the barrier increases, alpha decay is less likely

Question 43

Why are alpha particles more likely to be emitted than single protons/neutrons?

Answer 43

Conservation of wave function symmetry prevents single nucleon emission. Also high binding energy of the alpha particle.

Question 44

How big is the nucleus?

Answer 44

1.75 to 15 fm. Depending on the nuclide.

Question 45

Define mass defect?

Answer 45

The number of protons + the number of neutrons - the mass of the nuclide.

Question 46

What is the ground state spin parity of even-even nuclei?

Answer 46

0+

Question 47

What is usually the first excited state spin parity of even-even nuclei?

Answer 47

2+

Question 48

After how many half-lives do we usually reach secular equilibrium?

Answer 48

5ish

Question 49

how many nucleons can be stored in each level?

Answer 49

2J + 1

Question 50

How do you find the moment of inertia in a rotational band?

Answer 50

E = (hbar^2/2I)(2J + 1) where I is the moment of inertia.

Question 51

What is the promiscuity factor?

Answer 51

How far away a nuclide is from a shell closure. P = NpNn/(Np + Nn) where Np and Nn are the numbers of valence protons and electrons.

Question 52

What are the first seven magic numbers?

Answer 52

2, 8, 20, 28, 50, 82, 126

Question 53

When is a nuclei deformed?

Answer 53

If it has promiscuity factor greater than 4.

Question 54

What state will a 0+ nucleus feed?

Answer 54

0+ since they tend to feed similar states.

Question 55

What are the units of exposure?

Answer 55

Coulombs/kg or roentgens. Conversion is 3876 roentgens = 1 C/kg

Question 56

Exposure

Answer 56

Exposure = Gamma A/r^2

Question 57

Whats the difference between dose equivalent and absorbed dose?

Answer 57

The equivalent dose calculates how much damage is expected based on the absorbed dose and type of tissue.

Question 58

What are we likely to see in a fission graph?

Answer 58

A staircase pattern spaced by about 6MeV, the binding energy of a nucleon. Beware of log log plots as you can see this better on a linear scale.

Question 59

mean lifetime

Answer 59

t = 1/lambda

Question 60

What are the different cases for pairing energy?

Answer 60

0 if A odd, if nucleus is even-even then positive, if odd-odd then negative

Question 61

what leads to the formation of quantized energy orbitals?

Answer 61

nuclear potential

Question 62

what does nlj mean?

Answer 62

describes where nucleons can be. n is the principle harmonic oscillator phonon number like a frequency. l is orbital angular momentum (because we are in 3D). j is spin.

Question 63

why is g9/2 aligned?

Answer 63

because g is 4, so it is 4 +1/2

Question 64

energy of vibrational nuclei?

Answer 64

E = n_phononE_phonon

Question 65

energy of phonon in vibrational nuclei?

Answer 65

energy of first 2+ state

Question 66

is rotation collective behavior?

Answer 66

yes

Question 67

what does the collective behavior say about the speed of transitions between the states?

Answer 67

collective is faster because all the nucleons are doing the same thing. gamma lifetimes get shorter for collective states.

Question 68

energy spacing and moment of inertia

Answer 68

inversely proportional

Question 69

typical alpha energy

Answer 69

5 MeV which means non-relativistic kinematics OK

Question 70

kinetic energy of the alpha particle

Answer 70

T_alpha = Q/(1+4/A)

Question 71

ell barrier for alpha decay

Answer 71

favors decay to same state, not as strong as for beta decay though.

Question 72

energy spectrum of alpha and beta decay

Answer 72

alpha has these peaks and there are only two particles so the linear momentum is conserved and fixed. Beta has three particles emitted and so its more of a continuum.

Question 73

what does the wavefunction affect in beta decay?

Answer 73

lifetime.

Question 74

what does a change in parity say about the permitted multipoles?

Answer 74

E odd and M even

Question 75

what does no change in parity say about permitted multipoles?

Answer 75

E even and M odd

Question 76

which multipole in gamma decay is the most intense?

Answer 76

the one with the lowest l.