San José State University |
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applet-magic.comThayer WatkinsSilicon Valley & Tornado Alley USA |
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The Magnetic Moments ofthe Even p Odd n Nuclides from Helium (2) to Tin (50) |
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The magnetic moment of a nucleus is due to the spinning of its charges. One part comes from the net sum of the intrinsic spins of its nucleons. The other part is due to the rotation of the positively charged protons in the nuclear structure.

However nucleons form spin pairs with other nucleons of the same type but opposite spin. Therefore the net magnetic moment in magnetons of a nucleus due to the intrinsic spins of its nucleons should be: 0.0 .for an even-even nucleus, 0.87985 for an odd-odd nucleus, 2.79285 for an odd p and even n nucleus and −1.9130 for an even p and odd n nucleus.

Due to the Rotation of a Nucleus

The magnetic moment of a nucleus μ due to the rotation of its charges is proportional to ωr²Q, where ω is the rotation rate of the nucleus, Q is its total charge and r is an average radius of the charges' orbits. The angular momentum L of a nucleus is equal to ωr²M, where M is the total mass of the nucleus. The average radii could be different but they would be correlated. Thus the magnetic moment of a nucleus could be computed by dividing its angular momentum by its mass and multiplying by it charge; i.e.,

where α is a constant of proportionality, possibly unity. Angular momentum may be quantized. This would make μ directly proportional to Q and inversely proportional to M. More specifically μ should be proportional to Q/M. The charge is proportional to p and M is proportional to (p+γn), where γ is the ratio of the mass of a neutron to that of a proton; i.e., 1.001375. . Thus Q/M is proportional to p/(p+γn).

Previous studies found that there are critical values of proton or neutron numbers for which the magnetic moment is unusually high. The primary
critical value is 50, a so-called *magic number* indicating the filling of a nuclear shell. To a much lesser
extent 28, another nuclear magic number, is a critical value.

Here is the graph of the data.

Generally the magnetic moment is a small amount is the range of −2 to +2 magnetons independent of the number of protons. But there are a few cases outside of that range and their magnitudes might be related to the proton number.

The Magnetic Moments of the Even p, Odd n Nuclides | ||
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Proton Number | Neutron Number | Magnetic Moment (magnetons) |

2 | 3 | -2.12749772 |

4 | 5 | -1.1778 |

6 | 3 | -1.3914 |

6 | 5 | -0.964 |

6 | 7 | 0.70241 |

6 | 9 | 1.32 |

8 | 5 | 1.3891 |

8 | 7 | 0.71951 |

8 | 9 | -1.819379 |

8 | 11 | 1.53195 |

10 | 9 | -1.88542 |

10 | 11 | -0.661797 |

10 | 13 | -1.08 |

12 | 11 | 0.5364 |

12 | 13 | -0.85545 |

14 | 13 | -0.8554 |

14 | 15 | -0.55529 |

14 | 19 | 1.21 |

16 | 15 | 0.48793 |

16 | 17 | 0.64382112 |

16 | 19 | 1 |

18 | 15 | -0.723 |

18 | 17 | 0.633 |

18 | 19 | 0.8 |

18 | 21 | -1.588 |

20 | 19 | 1.02168 |

20 | 21 | -1.594781 |

20 | 23 | -1.3173 |

20 | 25 | -1.3274 |

20 | 27 | -1.38 |

22 | 21 | 0.85 |

22 | 23 | 0.095 |

22 | 25 | -0.78848 |

22 | 27 | -1.10417 |

24 | 25 | 0.476 |

24 | 27 | -0.934 |

24 | 29 | -0.47454 |

26 | 27 | -0.386 |

26 | 29 | 2.7 |

26 | 31 | 0.09044 |

26 | 33 | -0.3358 |

28 | 29 | -0.7975 |

28 | 31 | 0.35 |

28 | 33 | -0.75002 |

28 | 35 | 0.752 |

28 | 37 | 0.69 |

30 | 33 | -0.28164 |

30 | 35 | 0.769 |

30 | 37 | 0.875479 |

30 | 39 | 1.157 |

30 | 41 | 1.052 |

32 | 35 | -0.849 |

32 | 37 | 0.735 |

32 | 39 | 0.547 |

32 | 41 | -0.8794677 |

32 | 43 | 0.51 |

34 | 39 | 0.87 |

34 | 41 | 0.67 |

34 | 43 | 0.5350422 |

34 | 45 | -1.018 |

36 | 39 | -0.531 |

36 | 41 | -0.583 |

36 | 43 | -0.536 |

36 | 45 | -0.908 |

36 | 47 | -0.970669 |

36 | 49 | -1.005 |

36 | 51 | -1.018 |

36 | 53 | -0.33 |

36 | 55 | -0.583 |

36 | 57 | -0.413 |

36 | 59 | -0.41 |

38 | 39 | -0.348 |

38 | 41 | -0.474 |

38 | 43 | 0.543 |

38 | 45 | -0.829 |

38 | 47 | -1 |

38 | 49 | -1.0928 |

38 | 51 | -1.147 |

38 | 53 | -0.885 |

38 | 55 | -0.793 |

38 | 57 | -0.537 |

38 | 59 | -0.498 |

38 | 61 | -0.261 |

40 | 49 | -1.08 |

40 | 51 | -1.30362 |

40 | 55 | 1.13 |

40 | 57 | 1.37 |

40 | 59 | 0.42 |

42 | 47 | 8.3 |

42 | 49 | 8.81 |

42 | 51 | 9.93 |

42 | 53 | -0.9142 |

42 | 55 | -0.9335 |

42 | 57 | 0.375 |

42 | 59 | 0.375 |

42 | 65 | -0.92 |

44 | 49 | 8.97 |

44 | 51 | 0.861 |

44 | 53 | -0.787 |

44 | 55 | -0.641 |

44 | 57 | -0.719 |

44 | 59 | -0.206 |

44 | 61 | -0.32 |

44 | 65 | -0.22 |

46 | 55 | -0.66 |

46 | 57 | -1.05 |

46 | 59 | -0.642 |

48 | 55 | -0.81 |

48 | 57 | -0.7393 |

48 | 59 | -0.6150554 |

48 | 61 | -0.8278461 |

48 | 63 | -0.5948861 |

48 | 65 | -0.6223 |

48 | 67 | -0.6484259 |

50 | 59 | -1.079 |

50 | 61 | 0.608 |

50 | 63 | -0.8791 |

50 | 65 | -0.91883 |

50 | 67 | -1.00104 |

50 | 69 | -1.04728 |

50 | 71 | 0.6978 |

50 | 73 | -1.37 |

50 | 75 | -1.348 |

The graph of magnetic moment versus neutron number reveals 50 as a critical value.

Let μ be the measured magnetic moment, sp and sn be the presence or absence (1 or 0) of a singleton proton or neutron, respectively. The variables like p≅50 represent 1 or 0 depending upon whether 49≤p≤51. The regression results were

[9.2 ] [-7.8 ] [6.1 ] [0.3 ] [3.9 ] [1.9 ] [8.4 ]

The coefficient of determination (R²) for this equation is only 0.56, but the t-ratios for the coefficients, shown in square brackets indicate that μ is definitely dependent upon sp, sn, p/(p+γn), p≅50 and n≅50 at the 95 percent level of confidence..

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