Experimental study on the 3p size-resonance in thep- wave neutron strength function

Abstract

Using a silicon filtered fission neutron beam of an energy width of 20 keV around 143 keV we measured the total cross sections for 37 nuclides and elements having mass numbers between 87 and 140 and determined the p-wave strength functions. The 3P-resonance at A = 98 shows no splitting into the P3/2-P1/2 doublet.The narrow resonance peak and the following broad distribution of the p-strength function (A = 103 to 140) can approximately be reproduced by deformed optical model calculations. The spin-orbit term in the optical potential is consistent with the spin orbit force in the shell model. For nuclei around the closed (N= 50) neutron shell a shell effect in the p-wave strength function is indicated.

Experimental study on the electric polarizability of the neutron

“…To deduce the scattering length b' from the transmission cross section (1) the following cross sections averaged over the 20 keV band of the 143 keV beam [21] must be taken into account: the s-wave compound nucleus cross section and the p-and d-wave total cross sections. These quantities can be calculated with the corresponding strength functions S~ and distant level parameters R• defined by R'z=R [1--( Using So=0.65_0.15 [16], R~= 0.23, $1 =0.05 _+ 0.05 and R~ = 0.3 for Bi, the same procedure leads to 9.7 _+ 0.2 fm and 9.96 _+ 0.05 fm.…”

“…[20]. Cross section measurements at a median energy of 143 keV were performed in the silicon filtered fission neutron beam of the converter facility [21] at the FRM. The full half width is 20 keV.…”

Cross sections for neutrons of 1970 eV and contributions to fundamental neutron interactions

“…Neutrons of energies up to about 3 MeV are available in filtered beams from the intense fission radiation source of the RENT facility [20]. A long (127 cm) Si filter allows the selection of a 20 keV band at 143 keV medium energy [8]. Filter combinations of Pb with PE provide two broad spectra with medium energies of 1.30_+0.05 MeV and 2.1_+0.1 MeV [9], respectively.…”

“…Since the exact compensation of the nonresonant transmission through the 8~ filter (6 mm *-0.0097 or 2 mm -* 0.0029 atoms/barn) is important for the selectivity, we determined experimentally the optimal thickness for the compensation filters by transmission measurements. For this purpose an epithermal neutron beam from the reactor reflector and three differently filtered beams of 143 keV [8] and of medium energies of 1. The effect of the air displaced by the target has been taken into account in the determination of the target's cross section.…”

Experimental study onp-wave neutron strength functions for light nuclei

“…For nuclei of mass number A and neutrons with the energy E (wave number k) the corresponding cross section for elastic scattering 8-s. t is given as the sum of all /-wave partial cross sections bts which are the sum of/-wave resonance and shape elastic scattering. By means of the average collision function Ug these cross sections are written as For details we refer to [2] where explicite expressions for these quantities and for the cross sections are given.…”