Some rare isotopes are produced by neutrino-induced reactions in supernova (SN) explosions
(n-process). The isotope 92Nb decays to 92Zr with a half-life of 3.47 107 years. Although
this isotope does not exist in the present solar system, the initial abundance ratio for 92Nb/93Nb
at the time of solar system formation (SSF) have been measured in primitive meteorites. The
astrophysical origin of 92Nb, however, has remained unknown. The SN n-process origin for
92Nb has been proposed and the SN calculation has demonstrated the n-process origin of 92Nb.
The abundances of n-isotopes depend on neutrino temperatures. In the calculation, the average
energies of kT = 3.2, 4.0, 6.0 MeV for the electron neutrino, anti-electron neutrino, and the other
neutrinos (nm and nt ), respectively, were used. The observed ratio of 92Nb/93Nb 10????5 can be
explained by the n-process.