Synthesis of the Elements in Stars

this, the situation is not as complex as it might seem.Research in "classical" nuclear physics since 1932 has shown that all nuclei consist of two fundamental build- ing blocks.These are the proton and the neutron which are called nucleons in this context.As long as energies below the Ineson pmduction threshoM are not exceeded, all "prompt" nuclear processes can be described as the shufHing and reshuRhng of protons and neutrons into the variety of nucleonic packs called nuclei.Only in the slow beta-decay pmcesses is there any interchange be- tween protons and neutrons at low energies, and even there, as in the prompt.reactions, the number of nu- cleons remains constant.Only at very high energies can nucleons be produced or annihilated.Prompt nuclear processes plus the slow beta reactions make it possible in principle to transmute any one type of ' fth 'dK lty ' th th eeprocessesoperatca d have cenma e, w adding further gn general there is only one i c s rocessi slncc h a very long lifetime.T i24 b h cui've.e lD ther locess, t cu tlma c c lich lsobRrs at 22) 123~124, plodUccd by I'Rpld IlcUtloD burning ls responsible for t y rlchlsobarsat h l' burning is responsibe fo C, 0, Nc" Also h drogcn burning in these a er p n 4 tron sl T b d d onl lIl thc r Ne" (cf.Sec.III).The only exceptions up to this heaviest iso o point are deuterium, lithium, ery iu, , ss whexe lt ls e s ' h h th fore been assigned to R ra ically erneu ron- .D e cess.AsslgQ- Rctlvc c wl men 1" m er o -"'(half-life 2X10' years), and after another n cnt type 0 syQ cs, cess.g- nlcnt to thc c process Iox' R QUID cx' 0 XC130 re the resu tan 1 t Ileo decays in 12.6 hr to X d ' th hain instead of Te c d T "8 can be produced in is thus roduce in e s c Te"5 Tc"'7 an e ca h hT"'' d d ess alt oug e either the s or the r proces, g ca ture of neutronsonlyinawea si e in h f h I"'d 5m% of the chain resulting from t e ac rest and lightest isotope b either process and it is or i cannot be built by is or d T "4 are about thc loccss is dcIQRIi c .c l dT"'.Thi gg t th t ndant and Te"', Te, an e T t e"' and Tc"', to the r process.e the s r, and processes have een ma e ' d II 3 the separation of the isotopes in the duccd in the same process are connecte y s a e d 1 d fth od to b ow 1 1 the great increase d the enera tren o clear.In order to show ow n1olc c cRl y f the abun- ln Rbui1dancc ln tLie p h eaks linear plots o e a dances of the odd and even isotopes, respec ivc y, d II 3. The magic-number peaks s ' h odd-A and even-A nuclei.n in Fi s.II,2 an stand out clearly in ot o m MAGtC SHELL NUMSER Lo 'm ABUNDANCE PEAKS FOR N=eg + l.6- a (n, y) -RAPlDLY lN (&,)')-SLOW@' iN REP GiaNTS Sm Eu l50 +Te l , 140 ATOMIC, NEleHT {OOP) I30 dd A abundance peaks near A = 129 and nd 139 shorn on a linear scale.ee 'lg.C. AbQQ68Qce8 Rnd, Spnthe818 A881gnment8 Given in the Appendix The Appendix contains all o.t.. f ..e information we ave been able to collect which is relevant to the synt esis 24-ABUNDANCE PE'AKS FOR N=82 AND Z 50 2.0 (nP) -SLONLY lN 'RED GlaNTS CERTAIN -+- ~LS &I l. 6-uJ g l4- ~l.2 ILJ ' ' g by emitting a positron or captu g 0 rin a E e1ectron t e next step in the chain following the nucleus Xg~b eing Cd ~I(j8 )j 111 cases 111 which iven [an example is 48 1 d th d elopment of loops.In a11 cases they also ea to e ev chain will be the side of the loop which is in the main chain wi e determine y e d b the faster of the reactions (eit er neu- tron-capture or e ah ta-decay) which can take place.o ranch-dlstlnguls c wc h bctwccIl Iluclcl which 1lc ln thc wcR I'anc assed of a loop, and those which are completely by-passe Osmium Il idlllm