Some twenty years ago Ruthemann and Lang shot a monoenergetic beam of electrons in the keV range through a thin foil of aluminum and measured the energy distribution of the emergent electrons. They noticed that while most of the beam penetrated the metal without an appreciable loss of energy, there was a distinct group of electrons which lost very nearly 15 eV. When a different metal was substituted for aluminum, the same phenomenon was observed except that the characteristic energy loss differed from metal to metal. The explanation of this effect was not long in coming. Some of the electrons lost a certain definite amount of energy by exciting longitudinal plasma oscillations inside the metal at a frequency characteristic of the particular metal. This cost the electron a “quantum” of energy where ℏ is Planck’s constant; Pines called this quantum the “plasmon”. The experiment, and the Bohm and Pines theory of it, marked the beginning of research into the properties of solid‐state plasmas.
9. B. D. Osipov and A. N. Khvishchev, Zh. Eksperim. i Teor. Fiz. 43, 1179 (1962); https://doi.org/ZETFA7 B. D. Osipov and A. N. Khvishchev, Soviet Phys.‐JETP 16, 833 (1962); https://doi.org/SPHJAR B. Ancker‐Johnson and J. E. Drummond, Phys. Rev. 131, 1961 (1963); https://doi.org/PHRVAO B. Ancker‐Johnson and J. E. Drummond, Phys. Rev. 132, 2372 (1963).https://doi.org/PHRVAO
10. B. Ancker‐Johnson and M. F. Berg in, Proceedings of the Seventh International Conference on Physics of Semiconductors, Paris 1964, (Dunod, Paris, 1964), p. 513.
11. Y. T. Baiborodov, M. S. Ioffe, V. M. Petrov, and R. I. Sobolev, J. Nucl. Energy C5, 409 (1963).https://doi.org/JNCEAA
17. S. J. Buchsbaum and P. A. Wolff, Phys. Rev. Letters 15, 406 (1965). https://doi.org/PRLTAO C. C. Grimes, G. Adams and P. H. Schmidt, Phys. Rev. Letters 15, 409 (1965).https://doi.org/PRLTAO
18. L. C. Hebel and P. A. Wolff, Phys. Rev. Letters 11, 369 (1963); https://doi.org/PRLTAO L. C. Hebel, reference 5, p. 117.
19. G. A. Williams and G. E. Smith, I.B.M. J. Res. Devel. 8, 276 (1964).https://doi.org/IBMJAE
20. See, for example, B. Lax and J. G. Mavroides, Solid State Physics (Academic Press Inc., New York, 1960) Vol. II, p. 261; R. E. Michel and B. Rosenblum, Phys. Rev. 128, 1646 (1962); https://doi.org/PHRVAO G. E. Smith, I. C. Hebel and S. J. Buchsbaum, Phys. Rev. 129, 154 (1963).https://doi.org/PHRVAO
21. W. P. Allis. S. J. Buchsbaum and A. Bers, Waves in Anisotropic Plasma (The Massachusetts Institute of Technology Press. Cambridge. Massachusetts. 1963); T. H. Stix, The Theory of Plasma Waves (McGraw‐Hill Book Co., Inc., New York. 1962).
23. S. J. Buchsbaum and J. K. Galt, Phys. Fluids 4, 1514 (1961); https://doi.org/PFLDAS G. A. Williams, Phys. Rev. 139, A771 (1965); https://doi.org/PHRVAO M. A. Khaikin, V. S. Edelmann and R. T. Mina, Zh. Eksp. i. Teor. Fiz. 44, 2190 (1963); M. A. Khaikin, V. S. Edelmann and R. T. Mina, 45, 1704 (1963) (translation M. A. Khaikin, V. S. Edelmann and R. T. Mina, Soviet Phys.‐JETP 17, 1470 (1963); https://doi.org/SPHJAR M. A. Khaikin, V. S. Edelmann and R. T. Mina, 18, 1167 (1964); https://doi.org/SPHJAR, Sov. Phys. JETP B. W. Faughnan, J. Phys. Soc. (Japan) 20, 574 (1965).https://doi.org/JUPSAU
25. M. Surma, J. K. Furdyna, and H. Praddaude, Phys. Rev. Letters 13, 710 (1965).https://doi.org/PRLTAO
26. P. Aigrain in, Proceedings of the International Conference on Semiconductor Physics, Prague, 1960 (Czechoslovak Academy of Sciences, Prague, 1961) p. 224.
31. E. Kaner and V. G. Skobov, Zh. Eksperim. i. Teor. Fiz. 45, 610 (1963); https://doi.org/ZETFA7 E. Kaner and V. G. Skobov, Soviet Phys.‐JETP 18, 419 (1964).https://doi.org/SPHJAR
33. C. C. Grimes, reference 5, p. 87; D. A. Hays and W. L. McLean, Phys. Letters 17, 215 (1965).https://doi.org/PHLTAM
34. C. C. Grimes (private communication).
35. C. C. Grimes and S. J. Buchsbaum, Phys. Rev. Letters 12, 356 (1964); https://doi.org/PRLTAO for theory of helicon wave‐phonon coupling, see G. A. Akramov, Soviet Phys.‐Solid State 5, 595 (1963); https://doi.org/SPSSA7 J. J. Quinn and S. Rodriguez, Phys. Rev. 133, A1589 (1964); https://doi.org/PHRVAO D. N. Langenberg and J. Bok, Phys. Rev. Letters 11, 549 (1963).https://doi.org/PRLTAO
40. S. Ichimaru, D. Pines, N. Rostoker, Phys. Rev. Letters 8, 231 (1962); https://doi.org/PRLTAO P. M. Platzman, Phys. Rev. 139, A379 (1965); https://doi.org/PHRVAO A. L. McWhorter in, Proceedings of the Quantum Electronics Conference, San Juan, 1965 (to be published).
44. T. Misawa, J. Appl. Phys. (Japan) 2, 500 (1963); R. J. Briggs, Electron Stream Interaction with Plasmas (The Massachusetts Institute of Technology Press, Cambridge, 1964), p. 81.
45. D. J. Bartelink, to be published.
46. G. A. Baraff and S. J. Buchsbaum, Appl. Phys. Letters 6, 219 (1965).https://doi.org/APPLAB
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