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4 pages, 1 table, 4 figures.-- Printed version published Mar 11, 2002.-- PACS nrs: 24.30.Gd; 25.60.-t; 27.20.+n, Low-lying resonance states in He-7(He-6 + n), formed after fragmentation reactions of a 227 MeV/nucleon He-8 beam on a carbon target, have been studied. Coincidences between He-6 nuclei and neutrons, corresponding to the one-neutron knockout channel in He-8, were selected. The relative energy spectrum in the He-6 + n system shows a structure, which is interpreted as the He-7 (Iπ = 3/2(-)) ground state, unbound with 0.43(2) MeV relative to the He-6 + n system and a width of Γ = 0.15(8) MeV overlapping with an excited (Iπ = 1/2(-)) state observed at 1.0(1) MeV with a width of Γ = 0.75(8) MeV., This work was supported by the BMBF under Contracts No. 06 DA 915I, No. 06 OF 838, and No. 06 MZ 864 and by GSI under Contracts No. DA RICK, No. OF ELZK, and No. MZ KRAK and partly supported by the Polish Committee of Scientific Research under Contract No. KBN/2P03B/144/10, by the EC under Contract No. ERBCHGE-CT92-0003, by CICYT under Contract No. AEN92-0788-C02-02 (M. J.G. B.), by RFBR under Contract No. 01-02-16685, and by WTZ under Contract No. RUS 674-98. One of us (B. J.) acknowledges support by Alexander von Humboldt Research.

Magnetic dipole transitions in the self-conjugate nucleus ${}^{32}\mathrm{S}$ up to an excitation energy of 12 MeV have been investigated in inelastic electron scattering at ${\ensuremath{\Theta}}_{e}=180\ifmmode^\circ\else\textdegree\fi{}$ at the superconducting Darmstadt electron linear accelerator (S-DALINAC). Transition strengths have been determined from a plane-wave Born approximation analysis including Coulomb distortion. For the two strongest $M1$ transitions, where a discrepancy of a factor of about 2 was observed in previous ${(e,e}^{\ensuremath{'}})$ experiments, values intermediate between the two extremes are deduced from the present work. The resulting strength distribution is well described by shell-model calculations using the unified $\mathrm{sd}$-shell interaction and an effective $M1$ operator. The shell-model wave functions also provide a reasonable description of the form factors. A quasiparticle random phase approximation calculation is less successful. The present results allow for the first time studies of the form factor of extremely weak l-forbidden and isoscalar $M1$ excitations in ${}^{32}\mathrm{S}.$ The l-forbidden transition allows a sensitive test of tensor corrections to the $M1$ operator. A combined analysis with the isospin-analog Gamow-Teller (GT) transitions in the $A=32$ triplet reveals a situation similar to previous studies in $A=39$ nuclei: microscopic calculations reasonably account for the GT strengths, but fail in the case of $M1$ strengths. A possible explanation may be found in the nonrelativistic treatment of the latter. Some examples of the role of relativistic corrections are discussed. A consistent description of the reduced transition strength and the form factor of the isoscalar $M1$ excitation requires isospin mixing with the close-lying isovector transitions. The extracted Coulomb matrix elements are roughly within the limits set by the approximate constancy of the spreading width derived from the analysis of compound-nucleus reactions.

This paper is divided in three parts: (i) the measurement of yields and decay losses of Li and Be isotopes released from a thin foil tantalum target at the CERN/ISOLDE PS-Booster; (ii) results from beta-decay experiments on Be-12 and Be-14, an improved half-life of 21.49(3) ms has been obtained for Be-12; (iii) the beta-decay of C-9. An outline of the analysis procedure to determine the branching at high excitation energies is given. The ground-state branch has been determined to 54.1(15)%.

The GSI projectile fragment separator FRS has demonstrated with many pioneering experiments the research potential of in-flight separators at relativistic energies. Although the present facility has contributed much to the progress in the field of nuclear structure physics, major improvements are desirable in the future. The characteristics of the proposed next-generation facility at GSI, the Super-FRS, will be presented and compared to other projects. The Super-FRS is a large-acceptance superconducting fragment separator followed by different experimental branches including a combination with a new storage-cooler ring system. This system consists of a collector ring (CR) and a new experimental storage ring (NESR) which allow precision mass and lifetime measurements as well as in-ring reaction studies. The NESR can be operated in combination with an electron ring to measure electron scattering with exotic nuclei. This electron heavy-ion collider will open up new fields for nuclear structure research.

Deuteron breakup is studied in an electro-induced 2H(e,e′p) coincidence experiment at low momentum transfer and close to threshold. The longitudinal-plus-transverse (L+T) and longitudinal-transverse interference (LT) structure functions are deduced. In general, calculations based on the Bonn potential and including meson exchange currents and isobar configurations describe the data well. Surprisingly large deviations are observed for angular correlations of the LT contribution.

Deuteron breakup has been studied in a 2H(e,e' p) coincidence experiment at low momentum transfer and for energies close to threshold. The longitudinal-plus-transverse ( L+T) and longitudinal-transverse ( LT) interference cross sections are deduced. Nonrelativistic calculations based on the Bonn potential and including leading order relativistic contributions, meson exchange currents, and isobar configurations describe the ( L+T) data well. Surprisingly, large deviations of 30% to 45% are observed for the LT contribution.

In a kinematically complete experiment at the Mainz microtron MAMI, pion angular distributions of the $^3$He(e,e'$\pi^+)^3$H reaction have been measured in the excitation region of the $\Delta$ resonance to determine the longitudinal ($L$), transverse ($T$), and the $LT$ interference part of the differential cross section. The data are described only after introducing self-energy modifications of the pion and $\Delta$-isobar propagators. Using Chiral Perturbation Theory (ChPT) to extrapolate the pion self energy as inferred from the measurement on the mass shell, we deduce a reduction of the $\pi^+$ mass of $\Delta m_{\pi^+} = (-1.7^{+ 1.7}_{- 2.1})$ MeV/c$^2$ in the neutron-rich nuclear medium at a density of $\rho = (0.057^{+ 0.085}_{- 0.057})$ fm$^{-3}$. Our data are consistent with the $\Delta$ self energy determined from measurements of $\pi^0$ photoproduction from $^4$He and heavier nuclei., Comment: Elsart, 12 pages and 4 figures, Correspondent: Professor Dr. Dr. h.c. mult. Achim Richter, richter@ikp.tu-darmstadt.de, submitted to Phys. Rev. Lett

19 pages, 3 tables, 6 figures.-- PACS nrs.: 27.20.+n; 24.70.+s; 25.06.-t.-- Available online Dec 4, 2000., Dissociation of 227 MeV/u 8He in a carbon target has been studied in kinematically complete experiments. The data include the relative energy spectrum, angular distributions in the neutron knock-out channel (6He+n) as well as diffractive dissociation and inelastic scattering into the (6He+2n) channel. The data are compared with corresponding results from the well-known halo nucleus 6He. In both cases it is found that neutron knock-out is the dominating reaction channel. The relative energy spectrum (6He+n) shows a structure, which is interpreted as being due to the Iπ=3/2− resonance in the 7He ground state with about equal contribution from its Iπ=1/2− spin–orbit partner., The 7He resonance shows a spin alignment similar to that observed in 5He, but with a smaller anisotropy indicating that the structure of the 8He ground state is more complicated than that of 6He., The data in the (6He+2n) channel were used to identify resonances in the excitation energy spectrum of 8He. If the spectrum is interpreted as two overlapping resonances, the spin-parity assignment for these is found to be 2+ and 1−, respectively., This work was supported by the BMBF under Contracts 06 DA 820, 06 OF 474 and 06 MZ 864 and by GSI via Hochschulzusammenarbeitsvereinbarungen under Contracts DA RICK, OF ELZ, MZ KRK and partly supported by the Polish Committee of Scientific Research under KBN grant No. 2 PO3B 14418, EC under contract ERBCHGE-CT92-0003, CICYT under contract AEN92-0788-C02-02 (MJGB) and WTZ under contract RUS 674-98. One of us (B.J.) acknowledges the support through an Alexander von Humboldt Research Award. The authors acknowledge fruitful discussions with Horst Lenske, Sergei Fayans and Leonid Grigorenko.

Studies of nuclei far from the valley of beta stability are one of the main topics in nuclear structure physics today. The search for states with spatially extended — by far larger than the range of nuclear forces — and low-dense matter distributions, so-called “halo” nuclei, found predominantly in light neutron-rich nuclei is of special importance. Results of experimental investigations that probe the structures of halo nuclei are presented and consequences for nuclear models are drawn. Some examples of experiments performed at GSI with relativistic secondary beams are given where cross sections, momentum distributions, angular, energy and momentum correlations after breakup into core fragments and valence nucleons have been measured. These data permit the extraction of cluster and single-particle ground-state properties and demonstrate the presence of large low lying multipole strengths near the threshold for particle emission.

The ISOLDE RIB-facility at CERN has today been producing a vast range of radioactive beams since more than 30 years. The low-energy beams of ISOLDE will be complemented by a post-accelerator, REX-ISOLDE, currently being assembled. In order to convert the pseudo-DC, singly-charged beam from the ISOLDE mass separators into a cooled and bunched beam at higher charge states, a novel scheme of trapping, cooling, and charge-state breeding has been devised, using a linear Penning trap and an Electron Beam Ion Source (EBIS). This allows for subsequent acceleration by a short, cost-effective LINAC consisting of an RFQ, an IH-structure and three seven-gap resonators, reaching 0.8–2.2 MeV/u. The installation of REX-ISOLDE is well underway and the first post-accelerated radioactive beams are expected to be obtained during late 2000.

As a tool for studying the structure of nuclei far off stability the technique of gamma-ray spectroscopy after low-energy single-nucleon transfer reactions with radioactive nuclear beams in inverse kinematics was investigated. Modules of the MINIBALL germanium array and a thin position-sensitive parallel plate avalanche counter (PPAC) to be employed in future experiments at REX-ISOLDE were used in a test experiment performed with a stable 36S beam on deuteron and 9Be targets. It is demonstrated that the Doppler broadening of gamma lines detected by the MINIBALL modules is considerably reduced by exploiting their segmentation, and that for beam intensities up to 10^6 particles/s the PPAC positioned around zero degrees with respect to the beam axis allows not only to significantly reduce the gamma background by requiring coincidences with the transfer products but also to control the beam and its intensity by single particle counting. The predicted large neutron pickup cross sections of neutron-rich light nuclei on 2H and 9Be targets at REX-ISOLDE energies of 2.2 MeV A are confirmed., 11 pages, 8 figures

The 48Ca(e,e(')n) reaction has been investigated for excitation energies 11-25 MeV and momentum transfers 0.22-0.43 fm(-1) at the superconducting Darmstadt electron linear accelerator S-DALINAC. Electric dipole and quadrupole plus monopole strength distributions are extracted from a multipole decomposition of the spectra. Their fragmented structure is described by microscopic calculations allowing for coupling of the basic particle-hole excitations to more complex configurations. Comparison of the excitation spectrum of the residual nucleus 47Ca with statistical model calculations reveals a 39(5)% contribution of direct decay to the damping of the giant dipole resonance.

Already the first experiments to explore nuclear ground-state properties of exotic nuclei with heavy-ion storage rings proved the research potential of precision experiments with the new experimental technique. In this contribution the perspectives for reaction studies in storage rings with energetic exotic nuclei at internal targets and in a small electron–heavy ion collider will be addressed. The feasibility of such experiments will be discussed.

International audience; The existence of β-delayed particle emission allows one to study the β-strength distribution, and thereby the ground-state structure, of exotic drip-line nuclei. A time-correlation method has been applied to recent data on the heaviest Be-isotopes to determine their neutron branches. Improved results were obtained for 12Be and new results were found for the very short-lived neutron-emitter, 14Be.

17 pages, 3 tables, 5 figures, 1 appendix.-- PACS nrs.: 23.40.Hc; 27.20.+n., The β-delayed neutron branches from neutron-rich Be-isotopes have been measured with a setup sensitive down to thermal energies. For Be-14 a new value of P(n) = 101 ± 4% has been found for the total neutron-emission probability and an upper limit of 2.4% (95% confidence level) is imposed on the combination P(2n) + 3P(3n) of multi-neutron emission probabilities. Moreover, an improved value of P(n) = 0.50 ± 0.03% has been obtained for Be-12. A time-correlation method, previously developed for a continuous radioactive beam to determine neutron branching ratios, has been revised and adapted to the pulsed secondary beam at ISOLDE, CERN.

The fragment separator FRS at GSI was used as an energy-loss spectrometer to measure the longitudinal momentum distributions of {16,18}C fragments after one-neutron removal reactions in {17,19}C impinging on a carbon target at about 910 MeV/u. The distributions in the projectile frames are characterized by a FWHM of 141+-6 MeV/c for {16}C and 69+-3 MeV/c for {18}C. The results are compared with experimental data obtained at lower energies and discussed within existing theoretical models., 10 pages, 5 figures; uses elsart style; corrected list of authors; will be published in Phys. Lett. B

7 pages, 4 figures.-- Journal issue title: Radioactive Nuclear Beams., An experimental study of β-delayed charged particles (H, He, Be), neutrons and γ-rays that follow the Li-11 β-decay, clearly indicates a β-feeding to an exited state at 18.1 MeV in Be-11 with a large Gamow-Teller strength, B-GT greater than or equal to 1.0. The large strength of this β-transition implies a broad overlap of the Be-11* state at 18.1 MeV and the ground state of Li-11. The deduced width of this resonance is similar or equal to 1 MeV. A strong suppression of the branch from 18.1 MeV state into the Be-10+n channel is observed. This branch, with the largest decay energy, has a partial width less than 1% of the total width. A centrifugal barrier consideration fails to explain this effect. A possible consequence of the observed effect for the Li-11 structure is that the admixture of (p(1/2))(2) configuration in Li-11 might be small.

Break-up of secondary Li-11 ion beams (280 MeV/nucleon) on C and Pb targets into Li-9 and neutrons is studied experimentally. Cross sections and neutron multiplicity distributions are obtained, characterizing different reaction mechanisms. Invariant-mass spectroscopy for Li-11 and Li-10 is performed. The E1 strength distribution, deduced from electromagnetic excitation of Li-11 up to an excitation energy of 4 MeV comprises similar to 8% of the Thomas-Reiche-Kuhn energy-weighted sumrule strength. Two low-lying resonance-like structures are observed for Li-10 at decay energies of 0.21(5) and 0.62(10) MeV, the former one carrying 26(10)% of the strength and likely to be associated with an s-wave neutron decay. A strong di-neutron correlation in Li-11 can be discarded. Calculations in a quasi-particle RPA approach are compared with the experimental results for Li-10 and Li-11. (C) 1997 Elsevier Science B.V.

This paper analyses the financial deepening position of both Romania’s financial market in general and the rural financial market in particular. The indicator M2/GDP (20% in 1995) shows that Romania’s financial depth is far less than might be expected for a country with its level of GNP. Therefore, stability enforcing macro- economic, legal and monetary policies are necessary to create the enabling environment for effective and efficient financial intermediation which is crucial in the overall Romanian economic transformation process. However, Romanian rural bank intermediaries either do not wish to extend their services to small scale agriculture and rural enterprises or they do not have the scope in terms of variety, quality and efficiency of instruments/services to deal with this type of clientele. While the Romanian rural financial market is relatively "deep" with regard to the number of intermediaries, it is by no means so with regard to its monetarization and service array. Therefore, the paper goes on to propose possible financial innovations that intermediaries engaging in rural finance may seek to adopt in order to become capable of efficiently supplying their services to small scale rural enterprises.

A search for the Jπ = 1/2− spin–orbit partner of the Jπ = 3/2− ground state in 7He has been performed with the 7Li(d,2He) charge-exchange reaction. The results are incompatible with recent claims of such a state at very low excitation energy [Meister M et al 2002 Phys. Rev. Lett. 88 102501] but rather suggest a resonance with parameters Ex = (1.2+0.5 −0.4) MeV, Λ = (1.9+0.8−0.4) MeV. GT strengths deduced for the transitions to the lowest states in 7He are in remarkable agreement with ab initio quantum Monte Carlo calculations.

Neutron and He-6 momentum distributions from He-8 break-up reactions in a C target have been measured at 240 MeV/u. The two-neutron removal cross section was found to be sigma(-2n) = 0.27 +/- 0.03 b. The nature of the momentum distributions is interpreted in some simple reaction scenarios.

7 pages, 3 figures, 1 table., Transverse and longitudinal momentum distributions of 9Li fragments from 11Li break-up reactions in C, Al and Pb targets have been measured at 280 MeV/u. The two-neutron removal cross-section was measured to be σ(−2n) = 0.26 ± 0.02 b for the carbon target, σ(−2n) = 0.47 ± 0.08 b for the aluminum target and σ(−2n) = 1.9 ± 0.4 b for the lead target. No significant difference is observed between the narrow widths (FWHM ≈ 47 MeV/c) of the transverse and longitudinal momentum distributions of the 9Li fragments. The physical implications of this are discussed., This work was supported by the German Federal Minister for Research and Technology (BMFT) under Contracts 06 DA 641 I, 06 BO 103 and 06 MZ 106 and by GSI via Hochschulzusammenarbeitsvereinbarungen under Contracts DA RICK, BO FRE, F ELE, Mz KRD and partly supported by the Polish Committee of Scientific Research under Contract PB 1158/P3/92/02 and CICYT under contract AEN92-078%CO2-02 (MJGB).

Neutron angular distributions from violent break-up reactions of Li-11 and Be-11 have been measured at 28 MeV/u and 280 MeV/u and at 41 MeV/u and 460 MeV/u, respectively. The derived neutron momentum distributions show a narrow component in transverse momentum that is within uncertainties independent of beam energy and target charge. This component is suggested to be simply related to the momentum distribution of the loosely bound halo neutron(s) in the projectiles.

We report a search for gamma rays emanating from Coulomb excitation of fast (30-46 MeV/u) radioactive projectiles He-8, Be-11,Be-12,Be-14 interacting with a lead target. These are clearly identified by their Doppler shift. The 320 keV 1/2(-) --> 1/2(+)gamma transition from Be-11 was observed with a cross-section of 191 +/- 26 mb which is noticeably less than expected from the known lifetime and in the perturbation limit of pure Coulomb excitation. In the other nuclei rather stringent upper limits of 0.01 to 0.2 Weisskopf units, are placed on the hypothetical transition to 1(-) states.

The angular distributions of the forward neutrons in the exclusive (Be-10 + n) channel have been measured. They can be accounted for quantitatively and without free parameters in terms of Coulomb and diffraction dissociation. The results show that the transverse momentum distributions result from an interplay between the tail of the wave function (the halo) and the reaction mechanism.

The two-neutron removal reactions of beams of 11 Li, 14 Be and 8 He upon Be, Ni and Au targets were studied at 30 MeV/u. The cross sections and the neutron forward angular distributions were measured; they correlate strongly with the two-neutron separation energy of the projectile. Even though the coverage of the neutron detectors was limited, a rough neutron-neutron distribution could be extracted. A simplified interpretation of the data is presented.

The cross-sections and forward angular distributions of fast neutrons have been studied for the reaction (11Li, 9Li) at 29 MeV/u on targets of Be, Ni and Au. The cross-sections are large and arise essentially from peripheral reactions. The angular distributions of the neutrons are very narrow and indicate the existence of a neutron halo with radius of about 12 fm.

A novel method to explore nuclear structure with an electron heavy ion (eA) collider situated in the new experimental storage ring (NESR) for heavy ions within the framework of the GSI future project is presented. Concepts and possible experiments are outlined, and their specific advantages and disadvantages compared to currently available techniques are discussed.

Beta-coincidentγ-rays have been measured from implanted pure samples of12Be separated at the LISE3 spectrometer at GANIL. An intensity of 0.040(26) % can be estimated for the branching ratio of the isospin forbidden pure-Fermi transition to the 0+ excited state of12B and of 0.008(6)% of the transition to the 1−1 excited state. Both are taken to represent upper limits. The half-life has been re-measured to be 26.1(2.4) ms.

Angular distributions of ions passing through thin amorphous foils are calculated by means of a Monte Carlo method and of analytical multiple scattering theories. For the scattering potential a screened Coulomb potential is taken. The results of the different multiple scattering computations are compared with each other and with experimental angular distributions.

The elastic and inelastic scattering of 12 C, 12 C, 24 Mg, 24 Mg, 28 Si, 28 Si was studied at bombarding energies E c.m. = 5–18.8, 20–33, 29–36 MeV, respectively. The experimental arrangement includes two position sensitive detectors covering the angular ranges from O 124 = 20°–70°. The results are compared to calculations within the framework of the diffraction and optical model. A phase shift analysis is performed for the elastic scattering data of the 12 C+ 12 C system. It is shown that a shallow nuclei potential in needed to reproduce the 28 Si+ 28 Si results and that the 12 C, 12 C scattering shows evidence of resonance formation in the elastic channel.

The γ-decay of states in 41 K and 41 Ar populated in the reactions 2 H( 40 Ar, n) 41 K and 2 H( 40 Ar, p) 41 Ar has been investigated at a bombarding energy of 56 MeV. Using the Doppler shift attenuation method and three different stopping materials, mean lifetimes were determined for the states in 41 K at 980 keV (0.5±0.2 ps), 1560 keV (0.6 −0.2 +0.3 ps), 1698 keV (0.1 −0.1 +0.2 ps), 2144 keV (0.8 −0.2 +0.3 ps) and in 41 Ar at 1354 keV (0.664 −0.08 +0.09 ps). Shell-model calculations have been performed for the positive parity states in 41 K using a model space of a proton hole in the 1 d 3 2 and 2 s 1 2 orbits and two neutrons in the 1 f 7 2 orbit. The resulting excitation energies and electromagnetic properties of the low-lying states are in good agreement with experiment. An empirical value for a [ Y 2 s ] 1 contribution in the effective M1 operator is obtained.

The 3 H( 3 He, pα)n reaction has been studied in a kinematically complete experiment at 3 He bombarding energies between 0.31 and 2.80 MeV in order to detect a possible resonant energy dependence of the spin singlet ( T = 1) neutron-proton final state interaction (FSI). The data in the region of low n-p relative energies have been analyzed in terms of the Watson-Migdal formalism. Only a slight relative increase of the 1 S 0 n-p FSI is observed with increasing bombarding energy. This result is not easily related to the strong isospin violations found in the two-body reaction 3 H( 3 He, d) 4 He at similar 3 He energies.

In the mass symmetric system 40Ar+40Ca at 20 MeV/u neutrons and light charged particles were measured in coincidence with evaporation residues. The shape of the neutron energy spectra and their angular distribution show a preequilibrium component. Multiplicities were determined. The data are compared to phase-space calculations.

Cross sections for elastic scattering of 40 Ar on 40 Ca have been measured at energies E lab = 191, 236 and 272 MeV employing position-sensitive detectors and the method of kinematical coincidences. The experimental data are first compared with the ordinary and the generalized Fresnel models. Only the generalized Fresnel model describes the experimental data well. An optical model analysis with a Woods-Saxon potential yields an energy independent set of parameters ( V R = −21.76 MeV, r OR = 1.37 fm, a R = 0.45 fm; W 1 = −13.69 MeV, r 01 = 1.40 fm, a 1 = 0.36 fm) very similar to the one found in 40 Ca- 40 Ca scattering at corresponding energies. Values deduced for the total reaction cross sections for the three energies are in good agreement with those predicted by the generalized Fresnel model. The data are also compared with optical model calculations with the real part of the potential replaced by various microscopically determined potentials. The proximity, Fleckner-Mosel and the Krappe-Nix-Sierk potentials like the phenomenological optical model potential reproduce the measured data fairly well over several orders of magnitude.

In the mass symmetric system 40Ar+40Ca the emission of neutrons and light charged particles produced in central collisions was studied at an incident energy of 20 MeV/u. Heavy reaction products and light particles were measured inclusively as well as exclusively. The heavy reaction product data allow a separation of central and peripheral collisions. The mass difference between the observed heavy fragments and the compound system can be explained by the emission of light particles with Z ⩽ 2. For the neutrons clear evidence for preequilibrium effects is found from the shape of the energy spectra and angular distributions. The preequilibrium and equilibrium multiplicities and nuclear temperatures are extracted from the data. The experimental results are compared to various models. From a quantal phase-space model an average equilibration time is derived.

The principle of detailed balance has been tested in the reactions 27 Al ( p , α 0 ) 24 Mg ( Q = 1.600 MeV ) and 24 Mg (α, p 0 ) 27 Al ( Q = −1.600 MeV ) at bombarding energies Elabp = 1.35−1.46 MeV and Elabα = 3.38−3.52 MeV, respectively. Protons and α-particles were detected at θc.m = 177.7°. The relative strengths of two resonances at Ex = 12.901 MeV Jπ = 2+ and Ex = 12.974 MeV (Jπ = 1−) in 28Si excited in the forward and backward reaction agree within the experimental uncertainty δ = 0.0025 ± 0.0192. This experimental result is converted into a difference of phase angles for reduced widths amplitudes, Δξ = (0.3 ± 3)°, which is consistent with time reversibility.

Fine-structure measurements of the differential cross section in elastic and inelastic proton scattering at Ep ∼ 7.5 MeV from 88Sr near a 2 d 3 2 isobaric analogue resonance in 89Y exhibit strong correlations between the cr section fluctuations in the two different channels.

Single neutron and proton quasi-elastic transfer in both directions have been studied in collisions of 48 Ti onto 42 Ca at E Lab = 385 MeV. The main strength in the particle energy spectra lies below 12 MeV excitation energy and displays features specific to the reaction channel. A one-step direct transfer mechanism which includes core excitation describes the main features of the spectra.

Single nucleon transfer and single charge exchange have been studied for quasi-elastic collisions of 48Ti and 42Ca at Elab = 240, 300 and 385 MeV. Specific features below 12 MeV excitation energy are displayed in all of the measured particle energy spectra for each channel. These have been accounted for in the case of nucleon transfer by a one-step direct transfer mechanism in which all of the available hole and bound particle states in the donor and acceptor nucleus, respectively, have been included. This core excitation model was extended to single charge exchange (SCX) two-step transfers in which a proton and a neutron are exchanged. The absolute magnitude and distribution of strength in the SCX channel was obtained. The contributions from direct charge exchange via the isovector parts of the NN interaction has also been investigated in a microscopic model and is found to contribute of the order of 1–5% to the charge exchange cross section. The distribution of Fermi and Gamow-Teller strength is discussed.

A scintillation drift chamber operated with a gas mixture of 90% Ar + 10% N2 in the range of pressure between 50 and 150 torr is described. The position where a heavy ion transverses the chamber is determined in one dimension from the drift time of ionization electrons measured as the time delay between primary and secondary scintillation flashes; the other dimensions is derived by charge-division techniques from the charge of the electron swarm arriving at the end of the drift space. ΔE signals for particle identification were derived from both the collected charge and the total light amplitude. With 136Xe and 238U ions of 1.4 MeV/amu, position resolution, pulse height and pulse-height resolution were studied systematically. Best resolutions obtained were 0.5 mm and 0.3 mm, respectively, for the two dimensions and 4.7% for ΔE.

The excitation functions of the reaction 88 Sr(p, p 0 ) at θ lab = 90°, 130° and 165° were measured at the new Dynamitron-Tandem accelerator at Bochum in the energy range 5.90 ≤ E p ≤ 6.27 MeV, i.e. near the lowest s 1 2 . isobaric analogue resonance in 89 Y, in steps of 1.1 keV. These measurements were undertaken in order to demonstrate for the first time the existence of fine structure in the case where many (p, n) channels are open and where the isospin T states overlap. The mean level width Γ of the T compound states and the compound elastic contribution to the cross section were evaluated by means of fluctuation averaging. By comparing the measured cross section with an optical model plus resonance calculation, the total width Γ, the partial width Γ p and the resonance mixing phase of the T > state as well as the external versus internal mixing were determined. The behaviour of the mean coherence width as a function of energy is calculated and the mean compound nucleus contribution is also estimated by analyzing the data in terms of the optical model. Various Hauser-Feshbach formulas are tested and the dependence of the elastic enhancement factor on the transmission coefficient has been studied.

In the system 48 Ti + 42 Ca at a 48 Ti energy of E Lab = 385 MeV the 2n-stripping reaction leading to 46 Ti + 44 Ca shows a remarkably narrow structure at a total excitation energy of 17.8 MeV and an experimental width smaller than 350 keV. Similar structures have been found also in the 48 Ti + 26 Mg → 46 Ti + 28 Mg reaction. A possible tentative explanation is the mutual excitation of high spin states in the final nuclei.

A simple movable target holder for nuclear targets bombarded by intense light-and heavy-ion beams has been developed. It has been tested with proton and oxygen beams of the Dynamitron-Tandem accelerator on the low-melting-point targets selenium and busmuth. Significant improvements in maximum beam current with respect to breaking and evaporation of the targets were achieved.

A magnetic lens spectrometer of Siegbahn-Sla¨tis type has been installed at the Dynamitron-Tandem accelerator at Bochum such that measurements of continuous beta spectra even for short half-lives can be performed as well as the determination of discrete conversion lines in the multi-sweep mode. Electrons and positrons can be focussed up to an energy of 10.7 MeV with transmission up to about 8% or a resolution of about 1% depending on the width of entrance and central baffle inside the spectrometer. The system was tested by determination of the half-life of27Si, and the endpoint energy as well as the shape of the allowed spectrum of24Na. The quantities amount tot1/2=(4.206±0.008)s, W0=(1.390±0.001) MeV anda=(−1.10±0.21) %/m0c2, respectively.

Neutron emission in central collisions of the mass symmetric system 40Ar+40Ca was studied at an incident energy E/A = 20 MeV. The neutron energy spectra and angular distributions show clear evidence for a non-equilibrium component. The neutron multiplicity and the nuclear temperature are extracted from the data. Comparison with results from a quantum mechanical phase-space model gives an average equilibration time.