12P. B. Johnson and R. w. Christy, Phys. Rev. B 6, 4370(1972) Cardona, Am J Phys. 39, 1277(1971). 13J. M. Bennet, J. L. Stanford, and E J. Ashley, J. Opt. Soc. Am. 60, E. T. Arakawa, M. W. williams, R. N. Hamm, and R, H. Ritchie 224(1970) Phys. Rev. Lett. 31, 1127(1973):R. w. Alexander, G.S. I American Institute of Physics Handbook (McGraw-Hill, New York Kovenor, and R J. Bell, Phys. Rev, Lett, 32, 154(1974) 963), 2nd ed, Sec. 6-g Metals and evaporator supplies may be obtained from Electronic Space 15A.S. Barker, Jr, Phys. Rev. B 8, 5418(1973):Am. J. Phys. 42, Products. 854 So. Robertson Blvd Angeles, CA 90035 1123(1974) J or psi (a physicist's four-footed sonnet) Where is the thing beneath the thing? When can we say we have found it all? Is there an end or just a string That dangles down like an endless fall? Molecules, yes, and atoms, too Electrons we know and nuclei Neutrons, protons, the particle zoo And enter now the or psi Can we not try to knot the string To start from a bottom and see what grows? Plant us a seed and see what we get When unity doubles and does its thing And triples, quadruples, quintuples. Who knows What patterns will show? What world is there yet? 一 roger E. Clapp 36/Am J Phys. VoL 43, No. 7, July 1975 Simon, Mitchell, and Warson