Evidence from Voyager and ISEE-3 spacecraft Data for the decay of secondary K-electron capture isotopes during the propagation of cosmic rays in the Galaxy

New data from the cosmic ray experiment on the Voyager spacecraft confirms and extends earlier data from a similar experiment on the ISEE-3 spacecraft which indicates the possibility of the decay of certain K-capture isotopes dur- ing the interstellar propagation of galactic cosmic rays. These cosmic ray measurements, along with the cross section mea- surements, indicate that 25% of the K-capture isotopes 51 Cr and 49 V produced as secondaries have decayed at interstellar energy of 400 MeV/nuc. This suggests a possible interstellar energy gain 100 MeV/nuc out of the current interstellar en- ergy 500 MeV/nuc. This measurement suggests that the study of the K-capture isotopes may now have reached a level that will soon provide definitive information on the amount of re- acceleration that may occur during cosmic-ray propagation after an initial acceleration in the cosmic ray sources.