Stem-Gerlach deflection

In the last decade, magnetic nanoclusters with diameters of 1-10 nm and containing tens-to-thousands of atoms have been of great interest because their properties are critically dependent on size [4-10]. The total magnetic moment in free Fe, Co, and Ni clusters was determined as a function of size by measuring their Stem-Gerlach deflections [4, 5, 9], For example, at a low temperature of 120 K, for small Fe clusters (25 < N < 130 atoms), the moment was found to be 3 per atom, which is considerably higher than... 

The dependence of the Stem-Gerlach deflection profile on the magnetic field is interesting. The anomalous asymmetric deflection observed for magnetic clusters in a collision-free beam [2, 3] implies internal transfer between spin and orbital angular momenta mediated by spin-orbit coupling, since the total angular momentum must be conserved. 

When atoms are placed in a magnetic field, the energy levels of the electrons split into more than one component These splittings are small (no more than 10 3 eV, even in strong magnetic fields), but can be seen in the line spectra of atoms this is called the Zeeman effect. There are other manifestations. For example, in an inhomogeneous (i.e. non-uniform) field, a beam of atoms can be deflected, and splits into several components this is the Stem-Gerlach experiment, and is illustrated in Fig. 5.5. 

When a beam of He atoms similarly undergoes a Stem-Gerlach experiment, the beam passes through without being deflected. This implies that there is no magnetic field associated with the He atoms, even though there are two electrons present. Thus, the two electrons in the atom must have opposite spins—one "up" and one "down"— which cancel each other out and provide no overall magnetic moment. 

The origin of EPR spectroscopy lies in the fact that electrons have both electrostatic charge and spin angular momentum. The former is observed by electron-deflection from negatively charged surfaces, in for example, a cathode ray oscilloscope the latter is easily verifiable in the classic Stem-Gerlach experiment [29, 30] in which a beam of S-state silver atoms is observed to split into two separate beams... 

A Figure 6.24 Illustration of the Stem-Gerlach expeiimenL Atoms in which the electron spin quantum number (uij) of the unpaired electron is are deflected in one direction, and those in which ms is —j are deflected in the other. 

The spin of the electron was measured experimentally by Stem and Gerlach. A beam of silver atoms was passed through a strong inhomogeneous magnetic field. It was found that the beam divided sharply into two beams. One beam was deflected as though each atom were a... 

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