EMISSION OF HELIUM-ISOTOPES IN THE REACTION OF ABSORPTION OF STOPPED PI-MESONS BY LI-6,LI-7 NUCLEI

The results of measurements of the inclusive spectra of helium isotope s produced in the absorption of stopped pi- mesons by Li-6, Li-7 nucle i are presented. The data indicate the presence of a mechanism of knoc kout of He-3 and He-4 by the primary neutrons produced as a result of absorption of pions by a pn pair of the nuclear p shell. The probabili ty of the one-neutron emission reaction Li-7(pi, He-6g.s.)n is measure d and found to be Y = (1.1 +/- 0.2) X 10(-3) l/stopped pi-. An analysi s of the high-momentum components of the He-3 and He-4 spectra in an e ffort to search for the multineutron nuclei 3n and 4n has been carried out. There are no indications in favor of the existence of these syst ems in the nucleon-stable or quasistationary states. The upper limits on the probability of producing these systems in the bound state are m uch lower than in previous studies: Y(Li-6(pi-, He-3)3n) < 1 X 10(-5) l/stopped pi-, Y(Li-7(pi-, He-4)3n) < 2 X 10(-5) l/stopped pi-, and Y( Li-7(pi-, He-3)4n) < 3 X 10(-6) l/stopped pi-.