NEUTRINO FLUENCE AFTER r-PROCESS FREEZEOUT AND ABUNDANCES OF Te ISOTOPES IN PRESOLAR DIAMONDS Y.-Z. QIAN1 AND P. VOGEL

Using the data of Richter, Ott, & Begemann on Te isotopes in diamond grains from a meteorite, we derive bounds on the neutrino Ñuence and the decay timescale of the neutrino Ñux relevant for the supernova r-process. Our new bound on the neutrino Ñuence F after freezeout of the r-process peak at mass number AD 130 is more stringent than the previous bound (in units of 1037 ergs cm~2) F[ 0.045 of Qian et al. and Haxton et al., if the neutrino Ñux decays on a timescale s. In particular, it qü Z 0.65 requires that a Ñuence of F\ 0.031 be provided by a neutrino Ñux with s. Such a Ñuence may qü [ 0.84 be responsible for the production of the solar r-process abundances at A\ 124È126. Our results are based on the assumption of Ott that only the stable nuclei implanted into the diamonds are retained, while the radioactive nuclei are lost from the diamonds upon decay after implantation. We consider that the nanodiamonds are condensed in an environment with C/O[ 1 in the expanding supernova debris or from the exterior H envelope. This environment need not have the 13C/12C ratio of the bulk diamonds, since the Teand Xe-containing nanodiamond grains are too rare to a†ect that ratio. The implantation of nuclei would have occurred D104È106 s after r-process freezeout. This time interval may be marginally sufficient to permit adequate cooling upon expansion for the formation of diamond grains. The mechanisms of preferential retention/loss of the implanted nuclei are not well understood. Subject headings : elementary particles È nuclear reactions, nucleosynthesis, abundances È solar system: formation È supernovae : general