Neutron Binding Energies from (d,p) Reactions and Nuclear Shell Structure

Abstract

Using 14-Mev deuterons from the M.I.T. cyclotron, proton spectra have been measured for many heavy and medium atomic weight elements. The range of the protons was measured in aluminum foils by the method of "peaking" with a triple proportional counter. From the Q-value of the ground-state proton group (measured relative to a Q-value of 5.50 Mev for the aluminum ground-state group), the neutron binding energy of the residual nucleus has been obtained. These values are compared to the maximum gamma-ray energy obtained from thermal neutron capture, A few neutron binding energies have been measured from the (d } t) reaction and are compared with values obtained from the (7, n) threshold. Several neutron binding energies have been computed from radioactive decay energies and measured neutron binding energies. All neutron binding energies have been compared with the values predicted from the semi-empirical mass formula. A sharp drop in neutron binding energy of about 2.2 Mev occurs at the completion of the closed shell of 126 neutrons. A drop, a little greater than 2 Mev, occurs at 50 neutrons. There is also a decrease in the region of 82 neutrons. There also seems to be a decrease of about 1 Mev in the region of 29 neutrons, but this is not very conclusive.The differential cross section of the ground-state peaks from even Z, odd A isotopes at forward angles are much smaller (about a factor of ten) than the differential cross sections of the groundstate peaks from the same Z but even A isotopes. The groundstate peaks from Sn 117 and Pb 207 , however, are about 50 percent that of the even A isotopes.

Decay Scheme ofLa138

“…Using the measured value of L/K, 1.4dz0.25, and the theoretical results of Brysk and Rose 22 on the Z,/i£-capture ratio as a function of transition energy and atomic number, we find that the transition energy is 160±30 kev. This is in fair agreement with the La 138 -Ba 138 mass difference of 1.3±0.4 Mev estimated from the following closed cycle of reactions: La 139 (Y,^)La 138 (Q= -8.8±0.2 Mev) 23 ; Ba 138 (J^)Ba 139 (<2=3.0±0.3 Mev) 24 ; Ba 139 -^->La 138 (E^-= 2.27±0.02 Mev). 25 In conjunction with the measured half-life of (2.1db0.1)X10 n years for the electron capture activity, this value for the transition energy yields 215 log//=16.9 which appears to be somewhat large* for a second-forbidden unique transition (A/=3(no).…”

Levels inBi210from theBi209(d,Holm1, Burwell2, Miller3 1960Phys. Rev.24110View full textAdd to dashboardCite

“…As soon as reaction Q values in the lead region became available, it was pointed out [13][14][15] that an error of between 0.4 and 0.5 Mev existed in a closed cycle including neutron binding energies and ft-and a-decay energies. This cycle is shown in Fig.…”

β-decay studies of the transitional nucleusCu75and the structure ofIlyushkin1, Winger2, Rykaczewski3 et al. 2011Phys. Rev. C16070View full textAdd to dashboardCite

“…Low-lying 7/2 + states in this area of the nuclear chart have been interpreted as being due to a (g 9/2 ) 3 configuration rather than the g 7/2 single-particle state [28]. A splitting between the 77 Ge g , if assumed to be a g 7/2 single-particle state, and a g 9/2 second excited state would be too small to be compatible with the much larger energy separation required by spin-orbit coupling [29]. Therefore, it seems likely that these levels can be thought of as arising from the coupling of an odd nucleon and a Coriolis-broken pair of nucleons all adding their spins together.…”