Search for non-Paulian transitions in Na-23 and I-127

A new search of non-paulian nuclear processes, i.e. processes normally forbidden by the Pauli exclusion principle, was carried out by determining an improved upper limit for the spontaneous emission rate of protons in Na-23 and I-127. A large set-up of highly radiopure NaI(TI) crystals was employed; it was placed deeply underground at the Gran Sasso National Laboratory of I.N.F.N. The upper limit on the unit time probability of non-paulian emission of protons with energy E-p greater than or equal to 10 MeV is lambda less than or equal to 4.6 . 10(-33)s(-1). The corresponding limit on the relative strength (delta(2)) for the searched non-paulian transitions has been estimated to be delta(2) less than or similar to 1.0 . 10(-54). (C) 1997 Elsevier Science B.V.