Neutron Asymmetries and Energy Spectra from Muon Capture in Si, S, and Ca

Nuclear excitation function and particle emission from complex nuclei following muon capture

“…The calculation gives 20'Bi(p, p), "=4x10 '. (4) The activation results of Vil'gel'mova et al , ' "Si (g, p),"~= (5.3~1.0) x 10 ', sQK( p, p) = (3.2 + 0.6) x 10 ', are mentioned by the authors of Ref. 3 to be higher by an order of magnitude from what they expected on the basis of the above mentioned curve.…”

“…In a recent letter, ' we proposed a model which successfully accounts for the new experimental findings of Wyttenbach et al ' on charged particles emission rates following muon capture in a wide range of nuclei, as well as for the older data on p and n spectra and rates from emulsion experiments. 4 ' In the present article, we give details of the work sketched in the letter' and we expand it by considering the proton emission from an additional large number of nuclei, which were used in several recent activation experiments. "' Predictions on the emission of deuterons and n particles from various light and intermediate nuclei are also presented.…”

“…In all our calculations we take M* = 0.68 M for both the capturing and the formed nucleon, which value is consistent with nuclear calculations. " Integrating over d'q and the angle between k and p, and changing variables to dE=-dk, one obtains x~(p-k-@~(E.-k-E), (4) where R is a constant and we use units with 8= c =1. k, p, and q are the three-momenta of the neutrino, capturing proton, and born neutron, respectively.…”

“…A very similar expression is obtained" if, instead of using the values of Kikuchi and Kawai ' X"" is calculated from the nuclear optical potential.In the muon capture process, the initial exciton number is n, =2, with one proton hole and one excited neutron from the elementary reaction p, +P -n+ v, . From this stage only neutron emission can occur, the first exciton state from which a proton can be emitted being n=4.For the fraction of the reaction cross section which does not emit during equilibration, we use the well-known statistical model ofWeisskopf and Ewing,4' according to which the probability of emission of particle x with energy &" from a compound nucleus of excitation energy E is &"(~") = [(2. , +1)/m']m"~o "(~")[p"(U)/p. (E)]8 (15) where s"and m"are the spin and mass of the emitted particle, p"(U) is the level density function of the residual nucleus of excitation energy U, and p, (E) the level density function of the compound nucleus.…”

Feasibility study of nuclear transmutation by negative muon capture reaction using the PHITS code

“…Figure 1 shows the differential cross section of secondary neutron from negative muon capture on 40 Ca and 208 Pb. The experimental data [16,17] are also plotted. PHITS is in good agreement with experimental data at low emission energies for 40 Ca target, although it tends to overestimate for 208 Pb.…”