Spin/parity DJ=L parity change=(-)L Tony Weidberg Nuclear Physics LecturesĮxperimental Tests 1018 Half-life (s) 10-6 4 9 Energy E (MeV) Tony Weidberg Nuclear Physics Lecturesįermi b DecayTheory Consider simplest case: n decay. Angular momentum effects: Additional barrier Small compared to Coulomb but still generates large extra exponential suppression. at x=0 and x=t for Kt>1 and k~K gives for 1D rectangular barrier thickness t gives T=|D|2=exp(-2Kt) Integrate over Coulomb barrier from r=R to r=t V E t Tony Weidberg Nuclear Physics LecturesĪ-decay DEsep≈6MeV per nucleon for heavy nuclei DEbind(42a)=28.3 MeV > 4*6MeV Neutrons Protons Alphas Tony Weidberg Nuclear Physics LecturesĪlpha Decay Rates Gamow factor Number of hits, on surface of nucleus radius R ~ v/2R.Decay rate Tony Weidberg Nuclear Physics LecturesĮxperimental Tests Predict log decay rate proportional to (Ea)1/2 Agrees ~ with data for e-e nuclei. Tony Weidberg Nuclear Physics LecturesĪ Decay Theory Consider 232Th Z=90 R=7.6 fm E=34 MeV Energy of a Ea=4.08 MeV Question: How does the a escape? Answer: QM tunnelling Tony Weidberg Nuclear Physics Lecturesģ I iII iI radial wave function in alpha decay r nucleusīarrier (negative KE) small flux of real α I iII iI Exponential decay of y Tony Weidberg Nuclear Physics Lectures Experimental observation of anti-neutrinos Parity violation What is parity Experimental evidence for parity violation. Fermi theory (low energy approximation) 4 point interaction. Beta decays: Need neutrino hypothesis to explain continuous e energy spectra.
Crude but explains orders of magnitude change in rate with E(alpha).
g decays Summary: Alpha decays: understand rates from QM tunneling and simple picture of alpha pre-formed in nucleus. QM tunnelling and a decays Fermi theory of b decay and e.c. Presentation on theme: "Nuclear Physics Lectures"- Presentation transcript:Ībg Decay Theory Previously looked at kinematics now study dynamics (interesting bit).
0 kommentar(er)
