John Sweer^*,†

• Department of Physics, Rutgers University, New Brunswick, New Jersey 08903

David C. Langreth^†,‡

• Department of Physics, University of California, San Diego, La Jolla, California 92037
• Department of Physics, Rutgers University, New Brunswick, New Jersey 08903

John W. Wilkins^§

• Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853

• ^*This work was based in part on the dissertation notes of John Sweer, a pre-doctoral student at Rutgers University, whose untimely death occurred on October 26, 1973.
• ^†Work supported in part by the National Science Foundation Grants NOSO GP-29262 and GH-38995.
• ^‡Rutgers University Research Council Fellow.
• ^§Work supported in part by the National Science Foundation through Grant No. DMR74-23494.