Proton Spectra from He3+T and He3+He3 Fusion at Low Center-of-Mass Energy, with Potential Implications for Solar Fusion Cross Sections

Few-body nuclear physics often relies upon phenomenological models, with new efforts at the ab initio theory reported recently; both need high-quality benchmark data, particularly at low center-of-mass energies. We use high-energy-density plasmas to measure the proton spectra from ${}^3\mathrm{He}+\mathrm{T}$ and ${}^3\mathrm{He}+{}^3\mathrm{He}$ fusion. The data disagree with $R$-matrix predictions constrained by neutron spectra from $\mathrm{T}+\mathrm{T}$ fusion. We present a new analysis of the ${}^3\mathrm{He}+{}^3\mathrm{He}$ proton spectrum; these benchmarked spectral shapes should be used for interpreting low-resolution data, such as solar fusion cross-section measurements.