The Kinematics of an Electron with an Axis.

London, Taylor and Francis, 1927. Contemp. full cloth. Stamped in blind on titlepage. In: ""The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science"", Vol. III, Seventh Series. X,1360 pp., textillustr. and 19 plates. (Entire volume offered). Thomas' paper: pp. 1-22. Internally clean and fine.

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First printing - in full - of Thomas' paper on electron spin. The Thomas factor gives a correction to the spin-orbit interaction in quantum mechanics, which takes into account the relativistic time dilation between the electron and the nucleus of an atom.""In February 1926 the missing factor two was supplied (Nature vol. 117) by Llewellyn Thomas and has since been known as the Thomas factor. Thomas noted that earlier calculations of the precession of the electronic spin had been performed in the rest frame of the electron, without taking into account the precession of the electron orbit around its normal. Inclusion of this relativistic effect reduces the angular velocity of the electron (as seen by the nucleus) by the needed factor 1/2. Einstein was surprised. Pauli became converted."" (Pais ""Inward Bound"", p. 279).