GAMOW, G. [GEORGE]. - GAMOW'S ATOMIC MODEL.

Zur Quantentheorie des Atomkernes. Mit 5 Abbildungen.

Berlin, Julius Springer, 1928. Without wrappers. In "Zeifschrift für Physik, 51 Band., Dritte und Viertes Heft. Titlepage to Bd. 51. Pp. 165-308.(Entire issue offered). Gamov's paper: pp. 204-12., textillustr. A stamp on titlepage.

First printing of Gamow's first major contribution to physics, his theory of alpha-decay.

By 1928, George Gamow had solved the theory of the alpha decay via tunneling. The alpha particle is trapped in a "potential well" by the nucleus. In classic physics, it is forbidden to escape, but according to the then newly discovered principles of quantum mechanics, it has a tiny (but non-zero) probability of "tunneling" through the barrier and appearing on the other side to escape the nucleus. Gamow solved a model potential for the nucleus and derived from first principles a relationship between the half-life of the decay, and the energy of the emission. Alpha particles were first described in the investigations of radioactivity by Ernest Rutherford in 1899.

"One of the first applications of quantum tunneling was by the physicist George Gamow in 1928, soon after the development of quantum mechanics. Alpha particles, which consist of two protons and two neutrons, are emitted by some nuclei. For example, ordinary uranium, 238U, with a lifetime of 4.5 billion years, decays by emitting an alpha particle.
For decades alpha decay had presented a problem: the emitted alpha particles seemed to have too little energy to get out of the nucleus. The Coulomb barrier arises from the combined effect of the Coulomb repulsion between the alpha particle and the nucleus (both positively charged) and the nuclear force that attracts the two particles. The energy of the emitted alpha particle is less than the top of this barrier. Classically, the particle would be unable to get out of the nucleus, but it obviously does.
Gamow suggested that alpha particles tunnel through the barrier. If so, the half-life of the decay should depend on the width and height of the barrier, and it does: the lower and thinner the barrier, the greater the chance of penetrating it. As the alpha particle's energy increases, the particle sees both a lower and thinner barrier so the probability of getting through increases extremely rapidly. For example, the energies of the alphas emitted by 232Th and 212Po are 4.05 MeV and 8.95 MeV, respectively, while their respective half-lives are 14 billion years and 0.3 millionth of a second. Thus, a factor of about two in energy produces a difference in half-lives of sixteen orders of magnitude (that is, sixteen powers of ten)!" (Rigden, Building Blocks of Matter: A Supplement to the Macmillan Encyclopedia of , p. 393).

Parkinson "Breakthroughs", 1928 P.

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