Excitations in208Pb nearE x=5683 keV

A search for the recently proposed two-phonon octupole vibrational (2-POV) 4⁺ or 6⁺ state in²⁰⁸Pb at an excitation energy of 5683 keV has been performed using the²⁰⁷Pb(d,p),²⁰⁸Pb (p,p) and (,) reactions at high energy resolution. No evidence for a two-phonon excitation at this energy is found.This work was supported in part by the DFG under contract nr. II C4-Gr 894/2-1 and by the DFG-Graduiertenkolleg Struktur der Hadronen und Kerne under contract nr. Mu 705/3-1.     

Excitation functions and isomeric ratios in the reaction130Te (α,xpyn) for α-particle energies between 15 and 37 MeV

The¹³⁰Te(,n)¹³³Xe,¹³⁰Te(,p)¹³³I,¹³⁰Te(,pn)¹³²I and¹³⁰Te(, n)¹²⁹Te excitation functions for alpha particle energies between 14.7 and 36.5 MeV are presented. Excitation functions for the last three reactions are measured for the first time and more consistent results for (, n) are obtained. The isomeric ratios for the ( n), (, pn) and (, n) reactions were deduced. Calculations based on different theoretical models of equilibrium and preequilibrium decay are compared with the experimental results and discussed. Acceptable presentation of the energy behavior of the measured isomeric ratios was obtained when higher angular momentum depletion for preequilibrium emitted particles was included. The absolute values of the isomeric ratios however remain overestimated.We want to express our gratitude to Prof. Ts. Vylov and Dr. V. Brudanin (Dubna) who supplied us with measurement equipment, to Dr. Chr. Necheva for taking part in the experiments, to the U-200 cyclotron staff and to the direction of the Laboratory of Nuclear Reactions (JINR) for making the irradiation possible and to Dr. E. Dobreva (Sofia) for fruitful discussion of the experimental method. We wish to express our gratitude also to Prof. M. Uhl and the NEA data bank for making the computer code STAPRE available to us and to Prof. J. Ernst (Bonn) for fruitful discussions. This project has been completed with the financial support of the Committee for Science at the Council of Ministers under contract No. 644.     

Partition of excitation energy between reaction products in heavy ion collisions

In the single-particle approach a partition of the excitation energy between the reaction products in deep inelastic collisions of heavy ions are investigated. The role of the particle-hole excitations and the nucleon exchange is considered. The ratio of the projectile excitation energy to the total excitation energy for the reactions²³⁸U(1468 MeV)+¹²⁴Sn,²³⁸U(1398 MeV)+¹¹⁰Pd,⁵⁶Fe(505MeV)+¹⁶⁵Ho,⁷⁴Ge (629 MeV)+¹⁶⁵Ho and⁶⁸Ni(880 MeV)+¹⁹⁷Au is calculated. The results of calculations are in good agreement with the experimental data.We are grateful to Dr. N.V. Antonenko for valuable discussions. This work was supported partly by the Russian Minister for Education and Research under the Grant N2-61-13-28.     

Intermediate mass fragment production in (α +27Al) reaction at low energies

The energy spectra of¹²C and¹⁶O fragments emitted in 50 and 60 MeV-induced reactions on²⁷Al have been measured using Solid State Nuclear Track Detectors. These data are in good agreement with the predictions of a simple moving source model, indicating statistical emission of the fragments from a nearly equilibrated compound nucleus.We are thankful to Dr. C. Bhattacharya and Dr. S. Bhattacharya of VECC for some useful discussions. The cooperation and help extended by the crew of the VECC and of the Pelletron, Bombay, is thankfully acknowledged. Special thanks are due to Sri P.K. Das for his etching and scanning assistance, and to Sri T.K. Das for his help during the experiments. Our thanks are also due to the Director of Saha Institute for providing the facilities.     

Production of isomeric44V and42Sc in high energy heavy ion reactions

Beta-coincident-rays were measured from implanted⁴⁴V and⁴²Sc nuclei. These were selected after⁵⁸Ni+nickel reactions by means of the LISE3 spectrometer at GANIL. The production of the isomeric states was identified by detecting their typical-delayed-ray cascades. From the intensities of the detected-lines the ratio between isomer and ground-state production of⁴⁴V follows to be 1 to 3.0(4).on leave of absence from GSI Darmstadt.     

The decay of spin-isospin modes in a semi-infinite slab

The surface response for charge exchange (p, n) and (³He, T) reactions is studied in the-region using the semi-infinite slab model. The contribution to the total response from different decay channels, (NN, N, ), is calculated. These decay channels corresponds to the exclusive channels, (pp, p ⁺, ⁺), measured in recent (p, n) and (³He, T) experiments. The in-medium properties of the-resonance is taken into account by using microscopic calculations of the-width in nuclear matter. From the-width in nuclear matter a non-local imaginary-potential, as well as a local potential, is constructed for the semi-infinite slab model. The results in the semi-infinite slab model gives a qualitative understanding of the exclusive experiments. The exclusive (NN, N, ) channels are more sensitive, than the total response, tog-correlation parameters,-width and the absorption function used at the external vertex. Our calculations suggest low values of theg-correlation parametersg _N andg , (0.3). The results with the-width represented as a non-local or a local-potential are very similar, with only minor differences in the exclusive channels.Supported in part by the Swedish Natural Science Research Council and by the Director, Office of Energy Research, Office of High Energy and Nuclear Physics, Nuclear Physics Division of the U.S. Department of Energy under Contract No. DE-ACO3-76SF00098     

Critical scattering in heavy ion reactions

Heavy ion reactions at intermediate energies are mostly described by the VUU equations. Using methods of quantum statistics we derive a useful relation between the width of s.p. states and the density — density correlation function. Near the point of instability from this relation there follows the increase of the collision integral and enhanced equilibration.The author thanks Yu. Kalinovsky, R. Nazmitdinov and M. Di Toro for valuable discussions.     

Total neutron multiplicities as a measure of the violence in heavy ion reactions

Energy spectra and multiplicities of neutrons from the reaction system 838 MeV³²S projectiles on¹⁹⁷Au have been measured in coincidence with binary fragmentations. Neutron detection was performed simultaneously in a 4 scintillator sphere and by time-of-flight. The linear momentum transfer (LMT) and the excitation energyE _CN ^* are deduced with the folding angle technique. Neutron multiplicities are compared for consistency and discussed as a measure of LMT andE _CN ^* . The saturation ofM ₄ (E _CN ^* ) beyondE _CN ^* 400 MeV seen for several systems of high fissility (x0.8) is attributed to the spreading of the folding angle distribution and the increasing competition of charged particle evaporation.     

Comparison of the elastic and inelastic scatterings between152Sm+12C and148 Nd+16O

Angular distributions of elastic and inelastic scattering have been measured for¹⁵²Sm+¹²C at 63.2 MeV and¹⁴⁸Nd+¹⁶O at 90.9 MeV. An evident interference pattern in the inelastic scattering has been observed for the first time in a strong Coulomb coupling system.We are indebted to Dr. S. Pieper for supplying the Ptolemy Program. One of us (Chenglie Jiang) would like to acknowledge the Argonne National Laboratory for the opportunity given, to perform theoretical calculations with the code Ptolemy during his visit there. Thanks are also due to Mr. H. Folger (GSI, Germany) for supplying the targets. This work was supported in part by China National Nature Science Fundation.     

Excited states populated via nucleon transfer in the reaction32S +208Pb

The population strengths of excited states in nuclei produced via transfer reactions in the 185 MeV³²S +²⁰⁸Pb reaction have been investigated by heavy-ion- coincidence techniques. The cross sections extracted from the spectra, have been analyzed in the framework of the Complex WKB approximation theory.     

Protonium annihilation into two mesons

The available branching ratios for protonium annihilation into two mesons are analyzed in terms of a hadronic picture. We start from protonium wave functions calculated using a realistic OBE potential, a phenomenological part to account for the annihilation, and a particularly simple transition operatorV(N¯N meson _a + meson _b ). Flavour effects, sensitivity to tensor mixing and to isospin mixing are investigated.Work supported in part by German BMFT grant 06 OR 762, and by European Community project SC1-0233-C     

Phenomenological analysis of intermediate mass fragments emission in alpha induced reactions

Intermediate mass fragment emission in induced reactions on Al and Ti at 60 and 104 MeV, respectively has been analysed using phenomenological moving source model. Fragment emission at backward angles is found to be well explained by a single fusion-like source, whereas for forward angles an additional intermediate velocity source is required to explain the data. The relative contribution of the intermediate velocity source decreases sharply with angle for lower energies and it extends significantly to larger angles in the higher energy reaction. The fractional momentum transfer for the fusion-like source is in agreement with the corresponding Viola systematics value in the case of +Al reaction, whereas for +Ti reaction, it is larger than that obtained from the Viola systematics. The degree of incompleteness (in momentum transfer) is found to be fragment dependent; incompleteness being more for lighter fragments and vice-versa.     

New neutron-rich isotopes in the scandium-to-nickel region,produced by fragmentation of a 500 MeV/u86Kr beam

We have measured production cross-sections of the new neutron-rich isotopes⁵⁸Ti,⁶¹V,⁶³Cr,⁶⁶Mn,⁶⁹Fe,⁷¹Co and neighbouring isotopes that have been identified as projectile fragments from reactions between a 500 MeV/u⁸⁶Kr beam and a beryllium target. The isotope identification was performed with the zero-degree magnetic spectrometer FRS at GSI, using in addition time-of-flight and energy-loss measurements. The experimental production cross-sections for the new nuclides and neighbouring isotopes are compared with an empirical parametrization. The resulting prospects for reaching even more neutron-rich isotopes, such as the doubly-magic nuclide⁷⁸Ni, are discussed.This work is part of the Ph.D. Thesis of M. Weber     

Calculation of relativistic effects in sub Coulomb heavy ion scattering

Relativistic corrections for the elastic scattering of heavy ions in the sub Coulomb regime are given. The case of two identical particles is treated especially. The deviation from the Rutherford (Mott) cross section is calculated by using the Todorov equation and the Darwin Hamiltonian, resp. It is shown, that both approches lead to the same results for small kinetic energies. Furthermore we discuss the applicability of the WKB method for calculating the phase shifts and the possibility of using a classical perturbative approach in the case of nonidentical particles.     

Nuclear and electromagnetic fragmentation of 2.25-TeV197Au nuclei

We report the first measurement of the total charge-loss cross section _tot=_em+_nuc and partial cross sections (for Z=1, 2, ..., 9) of 11.4 A GeV¹⁹⁷Au nuclei in various targets. The large Coulomb barrier for Au reduces the electromagnetic contribution _em in a Pb target to only 18% of _nuc, compared with 70% for 14.5 A GeV²⁸Si and 120% for 200 A GeV³²S. With _em taken to be Z _T ^1.8 , _nuc can be fitted with _nuc=(A _P ^1/3 +A _T ^1/3 –b)², with b=0.83 and =59 mb, essentially the same as found at energies of 1 to 2 A GeV. Electromagnetic partial cross sections for Z=1 exceed 40 mb in the Pb, Sn, Cu, and Fe targets and are substantial for larger values ofZ in the heavier targets.We are indebted to D. Beavis and the staff of the Alternating Gradient Synchrotron at Brookhaven National Laboratory for producing the beam of 11.4 A GeV Au ions, to D. Snowden-Ifft for his efforts in developing the automated scanning system, and to S. Hirzebruch for a useful discussion. This work was supported in part by the Office of Energy Research, Office of High Energy and Nuclear Physics, Division of High Energy Physics, of the Department of Energy under contract No. DEAC03-76SF00098.     

Prompt fission induced by antiproton annihilation at rest on heavy nuclei

Antiproton induced fission probabilities of U²³⁸, Bi²⁰⁹, Pb²⁰⁸ and Au¹⁷⁷ are reported together with the mass distribution of the fission fragments in the U²³⁸ and Bi²⁰⁹ cases. The charged particles multiplicities observed in co-incidence with fission have, also, been measured for U and Bi and are presented.Dedicated to Peter Armbruster on the occasion of his 60th birthday in recognition of his important contribution to modern Nuclear Physics     

Energy dependence of collective flow of neutrons and protons in197Au+197Au collisions

We investigate the beam energy dependence of neutron and proton squeeze-out in collisions of¹⁹⁷Au+¹⁹⁷Au atE/A=400—800 MeV. The azimuthal anisotropy that describes the enhanced emission of mid-rapidity neutrons perpendicular to the reaction plane rises strongly with the transverse momentum of the neutrons. This dependence of the azimuthal anisotropy follows a universal curve — independent of beam energy — if the neutron momenta are measured in fractions of the projectile momentum per mass unit. Analogously, the kinetic energy spectra of mid-rapidity neutrons exhibit a universal behaviour as a function of the kinetic energy of the projectile. The members of the FOPI-collaboration: J.P. Alard, Z. Basrak, N. Bastid, I.M. Belayev, M. Bini, R. Bock, A. Buta, R. aplar, C. Cerruti, N. Cindro, J.P. Coffin, M. Crouau, P. Dupieux, J. Erö, Z.G. Fan, P. Fintz, Z. Fodor, R. Freifelder, L. Fraysse, S. Frolov, A. Gobbi, Y. Grigorian, G. Guillaume, N. Herrmann, K.D. Hildenbrand, S. Hölbling, O. Houari, S.C. Jeong, M. Jorio, F. Jundt, J. Kecskemeti, P. Koncz, Y. Korchagin, R. Kotte, M. Krämer, C. Kuhn, I. Legrand, A. Lebedev, C. Maguire, V. Manko, T. Matulewicz, G. Mgebrishvili, J. Mösner, D. Moisa, G. Montarou, P. Morel, W. Neubert, A. Olmi, G. Pasquali, D. Pelte, M. Petrovici, G. Poggi, F. Rami, W. Reisdorf, A. Sadchikov, D. Schüll, Z. Seres, B. Sikora, V. Simion, S. Smolyankin, U. Sodan, N. Taccetti, K. Teh, R. Tezkratt, M. Trzaska, M.A. Vasiliev, P. Wagner, J.P. Wessels, T. Wienold, Z. Wilhelmi, D. Wohlfarth, A.V. Zhilin.