EXPERIMENTAL TEST OF THE POSSIBLE VIOLATION OF THE PAULI EXCLUSION-PRINCIPLE BY PHOTOACTIVATION ANALYSIS OF CARBON CONTENT IN PURE BORON

Experiments which search for chemically boron-like carbon nuclei in sa mples of pure boron were carried out by a photo-activation technique. Use was made of the C-12(gamma n)C-11 reaction with irradiation by bre msstrahlung photons of below 30 MeV. The resulting positron active iso tope carbon-11 has a half-life of 20 min, and there are no radioactive nuclides formed by boron. These features of carbon-11 allow use of th e rather sensitive and selective gamma-gamma coincidence technique to detect carbon nuclei. Special radiochemical procedures were developed for purification of the samples from initial carbon and metal impuriti es in the samples. Experimental results provided an estimate of the li fetime of atomic electrons relative to the Pauli exclusion principle o f T > 10(21) yr. (C) 1998 Elsevier Science Ltd. All rights reserved.