(a) The chlorine solar-neutrino detector registers electron neutrinos only above ;…
PHYSICS · Subjective · Fermi University Physics · Nuclear Physics · Nuclear astrophysics and applications · Nuclear astrophysics and applications
The Nucleus Resolved, Ch Stellar burning and the origin of the elements
Problem
(a) The chlorine solar-neutrino detector registers electron neutrinos only above 0.814MeV; the gallium detector registers them above 0.233MeV. The two 7Be electron-capture lines are at 0.862MeV and 0.384MeV. State which of the two lines each detector can register. (b) In a neutron bath at Nn=1023cm−3 and kBT=100keV, the r-process path reaches the N=126 shell closure at Z=69 (thulium), A=195, where (n,γ)⇌(γ,n) equilibrium holds and the flow waits for beta decay. The stable nucleus that anchors the valley of stability at N=126 is 208Pb (Z=82). Once the neutron supply is exhausted, the waiting-point chain beta-decays at fixed mass number down to the first stable isobar, so the r-process abundance peak sits at A=195. State the mass-number displacement between this peak and the N=126 s-process peak, and say whether it falls inside the usual range of eight to thirteen mass units. (c) On the solar-system abundance curve, the deep hole at lithium, beryllium and boron and the smooth peak at iron are two separate features. Assign each to the process (or the absence of one) responsible, and give the one nuclear fact behind each.