Using the data of Richter et al .
( 1998 ) on Te isotopes in diamond grains from a meteorite , we derive bounds on the neutrino fluence and the decay timescale of the neutrino flux relevant for the supernova r -process .
Our new bound on the neutrino fluence { \cal { F } } after freeze-out of the r -process peak at mass number A \sim 130 is more stringent than the previous bound { \cal { F } } \lesssim 0.045 ( in units of 10 ^ { 37 } erg cm ^ { -2 } ) of Qian et al .
( 1997 ) and Haxton et al .
( 1997 ) if the neutrino flux decays on a timescale \hat { \tau } \gtrsim 0.65 s. In particular , it requires that a fluence of { \cal { F } } = 0.031 be provided by a neutrino flux with \hat { \tau } \lesssim 0.84 s. Such a fluence may be responsible for the production of the solar r -process abundances at A = 124 –126 ( Qian et al .
1997 ; Haxton et al .
1997 ) .
Our results are based on the assumption that only the stable nuclei implanted into the diamonds are retained while the radioactive ones are lost from the diamonds upon decay after implantation ( Ott 1996 ) .
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 ^ { 13 } C/ ^ { 12 } C ratio of the bulk diamonds as the Te- and Xe-containing nanodiamond grains are too rare to affect that ratio .
The implantation of nuclei would have occurred \sim 10 ^ { 4 } – 10 ^ { 6 } s after r -process freeze-out .
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 .