Capture of Negative Mesons by Nuclei

Abstract

SEVERAL writers¹ have commented on the unexpectedly long period which has been found for the nuclear capture of negative mesons from cosmic radiation at low altitudes (about 10^-6 sec. in aluminium²). It has been estimated³ that if this radiation fell on matter, the mesons would take about 10^-12 sec. to be slowed down by Coulomb interactions and to fall into 'K-orbits' around the nuclei. Consequently, the experimental value of 10^-6 sec. is the period for nuclear capture of a meson from the K-orbit⁴, in marked contrast to the value of 10^-16 sec. or less which has been predicted³ on the assumption that nuclear particles interact with each other through this meson field alone (apart from Coulomb interaction). The estimate of 10^-12 sec. for the slowing-down time has been questioned by Fröhlich⁵, but it seems to be generally believed that the time taken is much less than 10^-6 sec. and that there is, in fact, a big discrepancy between the experimental and theoretical values for the nuclear capture period.