Larmor Precession
When a torque is exerted perpendicular to the angular momentum L, it produces a change in angular momentum ΔL which is perpendicular to L, causing it to precess about the z axis. Labeling the precession angle as φ, we can describe the effect of the torque as follows: The precession angular velocity (Larmor frequency) is These relationships for a finite current loop extend to the magnetic dipoles of electron orbits and to the intrinsic magnetic moment associated with electron spin. There is also a characteristic Larmor frequency for nuclear spins. In the case of the electron spin precession, the angular frequency associated with the spin transition is usually written in the general form where γ is called the gyromagetic ratio (sometimes the magnetogyric ratio) and g is the electron spin g-factor. This angular frequency is associated with the "spin flip" or spin transition, involving an energy change of 2μB. An example for magnetic field 1 Tesla follows. The characteristic frequencies associated with electron spin are employed in electron spin resonance (ESR) experiments, and those associated with the nuclear spin in nuclear magnetic resonance (NMR) experiments. |
Index Magnetic force applications Magnetic field concepts Reference Rohlf, Sec 8-4 Larmor precession wiki | ||
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