7.3: Atomic Nuclei: Nuclear Magnetic Moment
All atomic nuclei are positively charged. When they have a nonzero spin, they behave like rotating charges. As a consequence of their charge and spin, these nuclei generate a magnetic field (B). This, in turn, gives rise to a magnetic moment (μ), which is randomly oriented in the absence of an external magnetic field. When an external magnetic field (B0) is applied, the magnetic moment vectors can align with the field or against it in 2
+ 1 orientations. A hydrogen nucleus, which is just a proton, has an value of ½ and two possible orientations. The orientation aligned with the field (called spin +½, spin-up, or α) has lower energy than the orientation aligned against the field (called spin −½, spin-down, or β).
