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phys3001: atoms, photons and fundamental particles > 7. Nuclear Properties > Flashcards

7. Nuclear Properties Flashcards

1
Q

Who invented the Plum Pudding Model?

A

JJ Thompson

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2
Q

Describe the plum pudding model

A

Tiny negatively charged electrons are spread through the atom, which must be positively charged since overall the atom is neutral. The atom is seen as a positively charged diffuse sphere of matter with electrons embedded in it.

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3
Q

Who first carried out Rutherford scattering?

A

Geiger and Marsden under Rutherford

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4
Q

Describe the process of Rutherford scattering

A

Alpha particles were fired at gold film. It was found that a small number of particles underwent large scattering angles (which is very unlikely in the plum pudding model).

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5
Q

What did Rutherford propose for the structure of the atom?

A

The planetary model of the atom. He proposed that atoms have a small positively charged core which contain most of the atomic mass.

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6
Q

Rutherford scattering is often regarded as the _____ __ ________ ________.

A

Birth of nuclear physics.

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7
Q

What assumptions are required to calculate the Rutherford cross section?

A
  • There is a Coulomb interaction between the alpha particle and the nucleus.
  • Scattering is elastic.
  • The target is thin enough to only consider single scattering.
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8
Q

What is the electric charge of a proton?

A

+1e

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9
Q

What is the mass of a proton?

A

1.6726 x 10^-27 kg (0.9383 GeV/c^2)

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10
Q

What is the spin of a proton?

A

1/2

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11
Q

What is the electric charge of a neutron?

A

0

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12
Q

What is the mass of a neutron?

A

1.6749 x 10^-27 kg (0.9383 GeV/c^2)

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13
Q

What is the spin of a neutron?

A

1/2

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14
Q

What is the parity operation?

A

An operator that reflects all spatial coordinates through the origin.

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15
Q

A physical property has _____ parity if it is invariant under the parity operation.

A

Even

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16
Q

A physical property has ____ parity if it changes sign under the parity operation.

A

Odd

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17
Q

Does a scalar property like temperature have odd or even parity?

A

Even: scalar quantities have no direction so are not impacted by the parity operation.

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18
Q

Does a vector property like velocity have odd or even parity?

A

Odd

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19
Q

Describe the signs of a wave function with even parity

A
20
Q

Describe the signs of a wave function with odd parity

A
21
Q

What determines whether or not a wavefunction has odd or even parity?

A

Whether or not it is symmetric

22
Q

State the parity operator

A
23
Q

Parity is ______ for particles because they are said to have ‘__________’ parity, so are either odd (-) or even (+).

A

Fixed
Intrinsic

24
Q

Particles with half-integer spins (fermions) have ________ parity to their anti-particles.

A

Opposite

25
Q

Particles with integer spins (bosons) have ___ _____ parity to their anti-particles.

A

The same

26
Q

The parity of two or more particles (a composite system) is given by the algebraic product of the ___________ _________ and an __________ _________ _____.

A

Individual parities
Angular momentum term

27
Q

Give the equation for the parity of 2 or more particles

A

P1, P2 = intrinsic parities
l = angular momentum

28
Q

Which two forces do not violate parity?

A
  • Strong nuclear force
  • Electromagnetic interactions
29
Q

Which force does violate parity?

A
  • Weak nuclear force (which involves beta decay)
30
Q

Why does beta emission violate parity?

A

Because a beta emission is preferentially in the direction opposite the nuclear spin.

31
Q

Give the classical equation for magnetic moment

A

µ = magnetic moment
e = electron charge
r = radius
v = speed
m = electron mass
l = angular momentum

32
Q

Give the quantum equation for magnetic moment

A

µ = magnetic moment
e = electron charge
m = electron mass
l = angular momentum

33
Q

What is the Bohr magneton?

A

µ_B = Bohr magneton
e = electron charge
m_e = electron mass

34
Q

What is the nuclear magneton?

A

µ_N = nuclear magneton
e = electron charge
m_p = proton mass

35
Q

What is the magnetic moment for protons and neutrons? (In terms of angular momentum)

A

µ = magnetic moment
g_l = orbital angular momentum g-factor (=1 for protons and =0 for neutrons)
l = angular momentum
µ_N = nuclear magneton

36
Q

Protons and neutrons have _________ _____ which also includes a magnetic moment.

A

Intrinsic spin

37
Q

What is the magnetic moment for protons and neutrons? (In terms of spin)

A

µ = magnetic moment
g_s = spin g-factor
s = spin (=1/2 for protons and neutrons)
µ_N = nuclear magneton

38
Q

What is the EXPECTED spin g-factor for protons and neutrons?

A

Neutrons: zero
Protons (and other spin 1/2 point particles): 2

39
Q

What is the spin g-factor for electrons?

A

-2.0023193043

40
Q

What is the spin g-factor for protons?

A

5.5856912

41
Q

What is the spin g-factor for neutrons?

A

-3.8260837

42
Q

What parity do protons have?

A

Even

43
Q

What parity do neutrons have?

A

Even

44
Q

Is a proton stable or unstable?

A

Very stable

45
Q

Is a free neutron stable or unstable?

A

Unstable

46
Q

Is the observed g-factor the same as expected for point particles?

A

No

phys3001: atoms, photons and fundamental particles (11 decks)

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