Number 60 (Story #2), December 27, 1991 by Phillip F. Schewe and Ben Stein BETA ENVIRONMENTAL FINE STRUCTURE (BEFS) is the name Steven E. Koonin of Caltech has given to the possible effect the crystalline environment may have on the electron energy spectrum from the beta decay of nuclei in a crystal. In an analogous process, called extended x-ray absorption fine structure, or EXAFS, the bumps in the spectrum of inner-shell electrons ejected from atoms in a sample by incident x rays are caused by the quantum interference of waves from the outgoing electron with waves reflected from surrounding atoms. The bumps in the spectrum provide information about the identity and spacing of atoms in the material. Koonin believes that similarly the energy spectrum of the electron emitted in the beta decay of a nucleus (in a crystal) may also exhibit bumps, and that these might arise from the interference of the outgoing electron wave and waves reflected back toward the nucleus. BEFS studies would have a bearing on the search for heavy neutrinos which involve tritium decays in solid-state detectors. (Nature, 12 Dec. 1991.)