The synthesis of Li⁷ and B¹¹ confronts astrophysicists. Type II (SN II) and Type Ic (SN Ic) supernovae are supposed to be the producers of these two elements. In this study we calculate the yields of these two elements for SN II progenitors with 8, 10 and 20 solar masses. The process considered here is the neutral current interaction of heavy flavour neutrinos (𝜈_𝜇 or 𝜈_𝜏) with He⁴ nuclei of the helium zone. The low mass progenitors are considered because the helium zone lies much closer to the core and hence experiences large neutrino flux. The starting point of the helium zone depends on detail stellar model. However, the shell radius at which it begins is available for these stars. 20 solar mass is considered for comparison of our production ratio Li/B with that of an earlier work. It is contrasted with the shock heating yields in the hydrogen envelope. The Li/B ratio has been found to be about 0.96. In the three model stars, the Li⁷ and B¹¹ yields are found to be in the range 6.61×10⁻⁶ −2.63×10⁻⁶ 𝑀_Sun and 6.92×10⁻⁶ −2.75×10⁻⁶ 𝑀_Sun respectively as we go from 8 to 20 𝑀_Sun. Some equivalence is found with shock induced nucleosynthesis model for SN II. The SN II yield is found to be compatible with that of hypernovae produced by C–O core collapse but higher than the yields obtained by neutrino processes in SNIc.

Yields of nature’s rarest isotopes La^{138} and Ta^{180} are calculated by neutrino processes in the Ne-shell of density $\rho ≈ 10^4 g/cc$ in a type II supernova (SN II) progenitor of mass 20 $M_\odot$. Two extended sets of neutrino temperature $- T_{\nue}$ = 3, 4, 5, 6 MeV and $T_{\nu(\mu/\tau)}$= 4, 6, 8, 10, 12 MeV respectively for charged and neutral current processes are taken. Solar mass fractions of the seeds La¹³⁹, Ta¹⁸¹, Ba¹³⁸ and Hf¹⁸⁰ are taken for calculation. They are assumed to be produced in some s-processing events of earlier generation massive ‘seed stars’ with average interior density range $\langleρ\rangle \approx 10^3−10^6 g/cc$. The abundances of these two elements are calculated relative to O¹⁶ and are found to be sensitive to the neutrino temperature. For neutral current processes with the neutron emission branching ratio, $b_n = 3.81 \times 10^{-4}$ and $b_n = 9.61 \times 10^{−1}$, the relative abundances of La¹³⁸ lie in the ranges $4.48 \times 10^{−14}−2.94 \times 10^{−13}$ and $1.13 \times 10^{−10} − 7.43 \times 10^{−10}$ respectively. Similarly, the relative abundances of Ta¹⁸⁰ lie in the ranges $1.80 \times 10^{−15} − 1.17 \times 10^{−14}$ and 4.53 \times 10^{−12}−2.96 × 10^{−11} respectively for the lower and higher values of the neutron emission branching ratio. For charged current processes, the relative abundances of La¹³⁸ and Ta¹⁸⁰ are found to be in the ranges $1.38 \times 10^{−9} − 7.62 \times 10^{−9}$ and $2.09 \times 10^{-11} − 1.10 \times 10^{−10}$ respectively. Parametrized by density of the ‘seed stars’, the yields are found to be consistent with recent supernova simulation results throughout the range of neutrino temperatures. La¹³⁸ and Ta¹⁸⁰ are found to be efficiently produced in charged current interaction.