TRIAC Progress Report - KEK

The reaction rate deduced from the data shown in Fig. 3-2 is faster by about one order
of magnitude at about T9 = 1 than the previously reported values. The fast reaction rate
is due to the resonance like structure in the excitation function of the reaction observed
at around Ecm = 0.9 MeV. The reaction rate of the 8 Li(d, t) 7 Li reaction is 3x10 3 cm 3 /s,
which is 45 times larger than those of the 8 Li(n, γ) 9 Li [3-2] and 8 Li(α, n) 11 B [3-3]
reactions at around T9 = 1.
Fig. 3-3. Reaction rate of the 8 Li(d, t) 7 Li reaction as a function of temperature . The red line
indicates the present result and the blue line represents the result of Balbes et al. [3-1].
The present result indicates that the 8 Li(d, t) 7 Li reaction could suppress the
synthesis of heavy elements through 8 Li when the number density of deuteron (Yd) is
comparable to those of neutron (Yn) and/or α particle (Yα). However, in the process of
nucleosynthesis in type II supernovae presently considered as a candidate of
astronomical sites for synthesizing heavy elements by rapid neutron captures (r-process),
the suppression would be negligible since the estimated Yd/Yn and Yd/Yα values are
very small at T9 =1 (about 10 -6 and 10 -8 , respectively). Figure 3-4 shows an example of
such considerations [3-5], where the relative reaction rates (YxY8Li) were
calculated and compared for several 8 Li-involved reactions. In the calculations, the
fraction of light elements, Yx (i.e. proton (Yp), deuteron (Yd), neutron (Yn) and alpha
particle (Yα)) were deduced by a network calculation for the r-process using the
neutrino-driven wind model in the Type II supernovae [3-6]. The environmental initial
parameters (i.e. electron fraction, entropy, etc.) in the model were selected to reproduce
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