Stern-Gerlach apparatus

Absolute zero via CSRR (for example isolation in position space by weighing or by Stern-Gerlach apparatus) ... 

But positional isolation via pure CSRR seems simpler and easier in principle, even if, via weighing, it may not be realizable in practice. But perhaps as discussed three paragraphs previously, via a Stern-Gerlach apparatus it may be [1], Its simplicity in principle allows us to focus on attainment of absolute zero per se rather on experimental technical issues. Moreover, as noted three paragraphs previously, the QCR method discussed in Sect. 3 of Ref. [1] employs purely-CSRR positional isolation as its first step as noted two paragraphs previously, only the de-excitation of atoms still in the first excited state down to the ground state in its second step is an ERR process. 

In summary, when an atom has a definite value of L, it has indefinite values of and Ly, but it has the latent ability to develop a definite, but completely unpredictable, value of either or Ly, provided, for example, that it interacts with a suitably oriented Stern-Gerlach apparatus. In such a process, it would, of course, develop an indefinite value for L. As a generalization of this result, as equations (28-30) show, on arbitrary rotation any given spherical harmonic Yp(6, (f)), becomes a linear combination of spherical harmonics with the same I, and coefficients that depend on the angle and direction of rotation. 

A schematic representation of the apparatus used by Stern and Gerlach. In the experiment, a stream of atoms splits into two as it passes between the poles of a magnet. The atoms in one stream have an odd T electron, and those in the other an odd 1 electron. 

Fig. 15.—Diagrammatic representation of Stern and Gerlach s apparatus. A molecular beam issues from the oven O, and passes between the pole-pieces of the magnet (one of which has the form of a knife-edge) to the receiving screen S.

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