Excitation functions of residual nuclei production from 40-2600 MeV proton-irradiated <Superscript>206,207,208,nat</Superscript>Pb and <Superscript>209</Superscript>Bi

The work is aimed at experimental determination of the independent and cumulative yields of radioactive residual nuclei produced in intermediate-energy proton-irradiated thin targets made of highly isotopic enriched and natural lead (^{206,207,208,nat}Pb) and ²⁰⁹Bi. 5972 radioactive product nuclide yields have been measured in 55 thin targets induced by 0.04, 0.07, 0.10, 0.15, 0.25, 0.6, 0.8, 1.2, 1.4, 1.6 and 2.6 GeV protons extracted from the ITEP U-10 proton synchrotron. The measured data have been compared with data obtained at other laboratories as well as with theoretical simulations by seven codes. We found that the predictive power of the tested codes is different but is satisfactory for most of the nuclides in the spallation region, though none of the codes agree well with the data in the whole mass region of product nuclides and all should be improved further.      

Excitation functions of <Superscript>6</Superscript>Li incomplete fusion reactions with Pt nuclei

Experimentally determined excitation functions of the transfer reactions producing ^194–199Au and ^197m Hg isotopes during the interaction of ⁶Li with Pt nuclei are presented. An analysis of the experimental data as compared to EMPIRE-2.18 model calculations and experimental results on the d + ^natPt and α + ^natPt reactions allow determination of the interaction channels of d- and α-clusters in ⁶Li with the target nucleus. The results from model calculations of the reaction cross sections appear considerably lower than the experimental data. This discrepancy in describing the reactions with weakly bound nuclei is probably associated with the incomplete consideration of various interaction channels in the EMPERE-2.18 software. It is clear that a complete understanding of the interaction pattern in these processes requires consideration of the direct channels of ⁶Li nucleus cluster transfer during ⁶Li breakup near the Coulomb barrier.     

Excitation functions for complete-fusion and transfer reactions in <Superscript>4</Superscript>He interaction with <Superscript>197</Superscript>Au nuclei

Excitation functions are measured for the fusion reactions ¹⁹⁷Au(⁴He, xn)^201?xn Tl that are induced by alpha-particle interaction with gold nuclei in the energy range 14–36 MeV and in which x neutrons (0 ≤ x ≤ 3) are evaporated. The stack-activation technique was used to record and separate reaction products. Experimental data on the fusion reactions followed by evaporation of one to three neutrons agree with results of previous studies. For the radiative-capture reaction ¹⁹⁷Au(⁴He,γ)²⁰¹Tl, the upper limit on the cross section proved to be much lower. The excitation functions for the reactions subjected to measurements are compared with the results of calculations based on the statistical model and with the results of an experiment performed previously in a ⁶He beam.     

1<Superscript>+</Superscript>(0<Superscript>+</Superscript>) state at 12.4 MeV in <Superscript>20</Superscript>Ne

Careful review of all the evidence makes it clear that at least three states are important at 12.4-MeV excitation in ²⁰Ne (four, if the broad (2⁺) at 12.5 MeV is included). The three states are 3 ^- , 0 ⁺ , and 1 ⁺ (0⁺). The latter, which is quite strong in ¹⁹F (³He, d) singles, is probably the state observed in coincidence with 6.13-MeV γ-rays in ¹⁹F(³He, dγ). Received: 19 August 2002 / Accepted: 28 October 2002 / Published online: 17 January 2003 RID="a" ID="a"e-mail: fortune@physics.upenn.edu Communicated by D. Guerreau     

The photoresponse of <Superscript>45</Superscript>Sc up to 7 MeV

High-resolution photon scattering experiments have been performed on the nucleus ⁴⁵Sc at the Darmstadt superconducting electron accelerator S-DALINAC using bremsstrahlung beams with end point energies of 5.0 and 7.0MeV. Energies, absolute cross-sections and decay widths of 50 states, most of them previously unknown, have been determined. The results are compared to (γ, ) experiments on the neighbouring closed proton shell isotope ⁴⁴Ca .     

A study of semi-classical processes in the elastic scattering of <Superscript>32</Superscript>S by <Superscript>64</Superscript>Ni and <Superscript>58</Superscript>Ni by <Superscript>27</Superscript>Al

In order to determine the extent of the presence of semi-classical phenomena such as Fresnel and Fraunhofer patterns etc., we have analyzed the elastic scattering of ³²S by ⁶⁴Ni and ⁵⁸Ni by ²⁷Al using the McIntyre parametrization at several energies. The theoretical approach can reasonably account for the general pattern of the data, thus allowing us to extract the parameters pertinent to these semi-classical processes. The scattering of ⁵⁸Ni by ²⁷Al at 220, 185, 170, 160 and 155 MeV laboratory energies, exhibits features expected from the strong absorption model (SAM). However, the features of the scattering of ³²S by ⁶⁴Ni at 150, 108, 98, 93, 91, 88 and 82 MeV laboratory energies have significant deviation from the expected pattern of SAM.     

Radiative strength function and the pygmy dipole resonance in <Superscript>208</Superscript>Pb and <Superscript>70</Superscript>Ni

The pygmy-resonance parameters and the E1 strength function are derived for ²⁰⁸Pb using a fully self-consistent microscopic formalism recently developed for magic nuclei, which takes into account quasiparticle phonon interactions (or coupling to phonons) in addition to the random phase approximation. For the radiative strength function of ²⁰⁸Pb at energies above 5 MeV, the experimental data of the Oslo group are adequately described by our predictions, whereby the important role of coupling to phonons is confirmed. By comparing the measurements based on the (³He, ³He′γ) and (γ, γ′) reactions, we discuss the physical properties of the radiative strength function measured for ²⁰⁸Pb. For the neutron-rich ⁷⁰Ni nucleus, predictions for the radiative strength function and the pygmy resonance are obtained using a partially self-consistent approach, which invokes the Skyrme forces in deriving the mean field, effective nucleon–nucleon interaction, and phonon characteristics.     

Data on photoneutron reactions from various experiments for <Superscript>133</Superscript>Cs, <Superscript>138</Superscript>Ba and <Superscript>209</Superscript>Bi nuclei

Basic methods for determining cross sections for photoneutron partial reactions are examined. They are obtained directly in experiments with quasimonoeneregetic annihilation photons or from the cross section for the (γ, xn) = (γ, 1n) + 2(γ, 2n) + 3(γ, 3n) +... neutron-yield reaction in experiments with bremsstrahlung photons by introducing corrections based on statistical nuclear-reaction theory. The difference in the conditions of these experiments, which leads to discrepancies between their results because of sizable systematic errors, is analyzed. Physical criteria are used to study the reliability of data on the photodisintegration of ¹³³Cs, ¹³⁸Ba, and ²⁰⁹Bi nuclei. The cross sections for partial and total reactions satisfying the reliability criteria are evaluated within the experimental–theoretical method (σ^eval(γ, in) = F_i^theor × σ^expt(γ, xn)) on the basis of the experimental cross sections σ^expt(γ, xn) and the results of the calculations within the combined model of photonuclear reactions.     

Analysis of <Superscript>8</Superscript>B Proton Halo Nucleus Scattered from <Superscript>12</Superscript>C and <Superscript>58</Superscript>Ni at Different Energies

Angular distributions in the elastic scattering of ⁸B from ¹²C and ⁵⁸Ni targets at different energies have been analyzed in the framework of the double-folding (DF) optical model. The real central part of the nuclear optical potential is obtained by folding the M3Y effective interaction with the cluster density distribution of the ⁸B nucleus. The experimental angular distributions have been successfully reproduced. This confirms the validity of the cluster structure of the ⁸B nucleus.     

New approximations to the energy dependences of the total cross sections for the proton-induced fission of <Superscript>197</Superscript>Au, <Superscript>203</Superscript>Tl, <Superscript>nat</Superscript>Pb,and <Superscript>209</Superscript>Bi nuclei

The total cross sections for ¹⁹⁷Au and ²⁰³Tl fission induced by protons of energy varied from about 200 to 1000 MeV with a step of about 100 MeV are measured. New approximations to the energy dependences of the cross sections for the proton-induced fission of ¹⁹⁷Au, ²⁰³Tl, natPb, and ²⁰⁹Bi nuclei are presented and discussed. For all of these nuclei, exponential functions are used as approximations.     

Photonuclear reactions on the cadmium isotopes <Superscript>106,108</Superscript>Cd at the bremsstrahlung endpoint energy of 55.5 MeV

The gamma-activation technique was used to measure the absolute yields of photonuclear reactions on the cadmium isotopes ^106,108Cd. The results obtained in this way were compared with the results of the calculations based on the statistical model. For reactions on the isotope ¹⁰⁸Cd, agreement between these theoretical and experimental results is good, but the experimental ratio of the yields of photoproton and photoneutron reactions on the isotope ¹⁰⁶Cd differs substantially from its theoretical counterpart. The results of our present study are discussed from the point of view of the production of bypassed nuclei in the p-process of nucleosynthesis.     

Analysis of <Superscript>4</Superscript>He+<Superscript>40</Superscript>Ca and <Superscript>4</Superscript>He+<Superscript>44</Superscript>Ti scattering using different optical model potentials

Elastic scattering of ⁴He+⁴⁰Ca and ⁴He+⁴⁴Ti reactions at backward angles has been analyzed using two differentmodels, microscopic and semimicroscopic folding potentials. The derived real potentials supplemented with phenomenological Woods–Saxon imaginary potentials, provide good agreement with the experimental data at energy E_c.m. = 21.8 MeV without need to renormalize the potentials. Coupledchannels calculations are used to extract the inelastic scattering cross section to the low-lying state 2+ (1.083 MeV) of ⁴⁴Ti. The deformation length is obtained and compared with the electromagnetic measurement values as well as those obtained from previous studies.