Uhlenbeck, George

Ubachs Wim, 150, 155 Ugalde Jesus M., 217 Uhlenbeck George E., 3, 10 Ulam Stanislaw Marcin, 260, 340,... 

One day as the Italian physicist Enrico Fermi and George Uhlenbeck (who had come to the United States on a visit) were looking out a window overlooking Manhattan, Fermi remarked, You realize, George, that one small fission bomb could destroy most of what we see outside Fermi was soon to be doing some of the preliminary experimental work that preceded the American atomic bomb project. It was Fermi who produced the first controlled nuclear chain reaction. 

The concept of electron spin was developed by Samuel Goudsmit and George Uhlenbeck in 1925 while they were graduate students at the University of Leyden in the Netherlands. They found that a fourth quantum number (in addition to n, t, and me) was necessary to account for the details of the emission spectra of atoms. The new quantum number adopted to describe this phenomenon, called the electron spin quantum number (ms), can have only one of two values, + and — j. 

The next day, in a letter to George Uhlenbeck at Columbia, quite something became might very well blow itself to hell. One of Oppenheimer s students, the American theoretical physicist Philip Morrison, recalls that when fission was discovered, within perhaps a week there was on the... 

Samuel Abraham Goudsmit (1902-1978). Dutch-American physicist. While a student of Paul Ehrenfest at the University of Leiden in 1925, he and fellow student George Uhlenbeck postulated the existence of intrinsic electron spin. Goudsmit was the scientific leader of Operation Alsos at the end of World War 11, whose mission was to determine the progress of German efforts toward an atomic bomb. 

George Eugene Uhlenbeck (1900-1988). Dutch-American physicist. Born in Indonesia (then a Dutch colony), Uhlenbeck studied at the University of Leiden with Paul Ehrenfest, where he, with fellow student Samuel Goudsmit, postulated the existence of intrinsic electron spin. In addition to his work on quantum mechanics, Uhlenbeck made fundamental advances in statistical mechanics and the theory of random processes. 

The "electron-spin hypothesis was formulated in 1925 by George Uhlenbeck and Samuel Goudsmit to account for the splitting of spectral lines in a magnetic field. The spinning of the electron is not known to be a real physical phenomenon. 

Attempts to explain this in terms of the Bohr theory and quantized angular momentum of electrons in their orbits failed. Finally, in 1925, George Uhlenbeck and Samuel Goudsmit proposed that this result could be explained if it was assumed... 

Many years ago while at a meeting, the author approached George Uhlenbeck, a prominent theoretical [ ysicist, and asked him to comment on this question. He simply stated Iireversibility is just a human illusion. Who knows if his opinion is correct ... 

Wave mechanics provides three quantum numbers with which we can develop a description of electron orbitals. However, in 1925, George Uhlenbeck and Samuel Goudsmit proposed that some unexplained features of the hydrogen spectrum could be understood by assuming that an electron acts as if it spins, much as Earth spins on its axis. As suggested by Figure 8-32, there are two possibilities for electron spin. Thus, these two possibilities require a fourth quantum number, the electron spin quantum number mg. The electron spin quantum number may have a value of + (also denoted by the arrow T) or — (denoted by the arrow i) the value of mg does not depend on any of the other three quantum numbers. 

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