Muon attachment in prompt fission of237Np

The probabilities of muon attachment to fission fragments in the prompt fission of²³⁷Np have been determined as a function of fragment mass and total kinetic energy release in a ( ^–,f ₁ f ₂ e ^–)-coincidence measurement. A strong dependence of the attachment probability on the fragment mass is observed. The experimental results are compared with theoretical predictions.It is a pleasure to thank Professor T. Mayer-Kuckuk for his co-operation in performing the project. We gratefully acknowledge the permanent support of Professor J.P. Blaser and his staff at PSI. We thank Professor R. Engfer, Dr. A.v.d. Schaaf, and Dr. H.C. Walter for their support in using the electron spectrometer SIN-DRUM I. We are thankful to Professor S. Polikanov (GSI) and to Dr. T. Krogulski (University of Warsaw, Bialystok) for intensive and fruitful discussions. We appreciate the collaboration of Professor W. Müller and Dr. J. Pauwels (CBNM-Mol) in the target preparation. This work has been funded by the German Federal Minister for Research and Technology (BMFT) under the contract number 06BN271 (PD, HH, FR, ChR, WS). We thank the following institutions and organisations for financial support: Foundation for Fundamental Research on Matter (FOM), the Netherlands Organisation of the Advancement of Pure Research (NWO) (JK, CdL, AT), and the Swiss National Foundation (SNF) (WB, EH; HP, DV). One of the authors is grateful for a fellowship granted by the Studienstiftung des deutschen Volkes (FR).     

Neutral meson production in relativistic heavy ion collisions

The production of ⁰ and mesons has been studied in the reactions²⁰Ne +Al at 350 MeV/u and⁴⁰Ar + Ca at 1.0 GeV/u. Rapidity distributions and transverse momentum spectra have been measured and are compared to thermal distributions.Dedicated to Prof. Dr. P. Kienle on the occasion of his 60th birthday     

Dynamical and thermal aspects of relativistic heavy-ion collisions

Within a covariant BUU-approach we simulate heavyion collisions at various bombarding energies from 400 MeV/u to 1 GeV/u. We evaluate locally the energymomentum tensorT ^v (x), and extract pressures, energydensities and temperatures. The connection of these thermodynamical quantities to experimental observables and their sensitivity to the equation of state is discussed. Furthermore, we investigate the question of local equilibration and evaluate the entropy produced in these reactions.Dedicated to Prof. Dr. P. Kienle on the occasion of his 60th birthday. Work supported by BMFT and GSI Darmstadt     

Phenomenological wave functions for the massA=14 system and a consistent description of beta decay observables

A set of phenomenological wave functions has been derived to describe the¹⁴N ground state and the isospin triplet consisting of the¹⁴C ground state, the first excited state of¹⁴N at 2.313 MeV and the¹⁴O ground state. Elastic and inelastic electron scattering form factors, the magnetic moment of the¹⁴N ground state and the shape factors in the ^± decay have been employed in a multiparameter fitting procedure to determine the amplitudes of the wave functions inL-S coupling. The inclusion of the beta decay observables in the fit has become possible for the first time since exact formulas for the shape factor in higher order do exist. The set of wave functions deduced exhibit predominately anL=0 contribution for the 0⁺; 1 states andL=1 and 2 contributions of nearly equal weight for the 1⁺; 0 state. It was observed that the inclusion of the shape factors allowed a more stringent determination of the amplitudes compared to previous attempts reported in the literature and led in the case of the 0⁺; 1 states to wave functions that show a small but noticeable difference within the isospin triplet. Besides the observables used for the fit, the radiative width (M1) of the 2.313 MeV state in¹⁴N can be described quite well with the derived wave functions, and in addition it has become possible to predict the pathological largeft ^– value of the¹⁴C decay and theft ⁺ value of the¹⁴O decay precisely. The wave functions are also applied to calculate the¹⁴N(, ⁺) cross section.Dedicated to Prof. Dr. P. Kienle on the occasion of his 60th birthday. Supported by the German Federal Minister for Research and Technology (BMFT) under contract number 06DA 184I     

Simultaneous formation of contacts and diffusion barriers for VLSI by rapid thermal silicidation of TiW

The formation of (Ti_xW_1–x)Si₂/(Ti_xW_1–x)N, by rapid thermal processing of Ti_xW_1–x on Si in an N₂ ambient is investigated. An activation energy of 1.7 eV is obtained for silicide formation. A distinct snow-ploughing of As atoms is observed during silicide formation whereas the interfacial B concentration decreases with increasing silicide formation temperature. The diffusion barrier properties of the (Ti_xW_1–x)Si₂/(Ti_xWi_1–x)N stack in contact with Al is investigated upon post-metal annealing. No interaction between the layers is found for temperatures as high as 475°C after 60 min. The improved thermal stability of the (Ti_xW_1–x)N layer in contact with Al is attributed to nitrogen blocking of the grain boundaries.     

Experimental evidence for muonicX-rays from fission fragments

In the spectrum of muonic X-rays of²³⁸U measured in coincidence with prompt fission events a structure has been found which is attributed to 2p1s transitions of the muon attached to heavy fragments. The intensityI _s of this structure relative to the strengthI _pf observed for prompt fission has been determined to beI _s/I _pf=(6.0± 2.1) %. Although the experimental significance for the appeareance of this phenomenon is weak, this is the first experimental indication for its occuxence.We are indebted to the following institutes or organizations for financial support: Bundesministerium für Forschung und Technologie der Bundesrepublik Deutschland contract number 06BN271 (CR,PD,HH,FR,WS), Foundation for Fundamental Research on Matter (FOM) and the Netherlands Organization of the Advancement of Pure Research (NWO) (JK,CTAMdL,AT), the Swiss National Foundation (SNF) (LAS,LS), and the Heinrich-Hertz-Foundation (HH) (FFK,BS).     

Interacting boson-fermion model analysis for159Tb

The result of an IBFM multilevel calculation with the 3s _1/2, 2d _3/2, 2d _5/2 and 1g _7/2 single particle orbits are reported for the first time for the positive parity states of the odd mass nucleus¹⁵⁹Tb. Comparisons are made with experimental data for energy spectra, transition probabilities, mixing ratios, electric quadrupole and magnetic dipole moments. The agreement with the low-lying spectra suggests an extended comparison up to levels with spin 25/2, thereby testing the predictive power of the model.We would like to thank Dr. D. Mac Mahon and the staff at the Imperial College Reactor Centre for their help and use of facilities. We would also like to thank Dr. P. Van Isacker for many illuminating discussions.     

Proton-proton and deuteron-deuteron correlations in interactions of relativistic helium nuclei with protons

The reactions⁴Hep pp+X,³Hep pp+X and⁴Hep ddp have been investigated and the correlation function has been measured for protons and deuterons with small relative momenta. Strong positive correlation has been observed for protons related mainly to the final state interactions in¹S₀ state. The root mean square radius of the proton source calculated from the correlation function has been found to be equal to (1.7±0.3) fm and (2.1±0.3) fm for⁴He and³He respectively. It agrees with the known radii of these nuclei.We would like to thank Dr R. Lednicky for discussion, helpful suggestions and for making available the computer program that calculates the theoreticalpp correlation function. The authors also thank Dr D.H. Boal for providing the results of the two-deuteron correlation function calculations.     

Short orbit distribution in the semiclassical limit of the SU(3) nuclear model

Three different families of short periodic orbits in the semiclassical SU(3) nuclear model were studied and their stability calculated. Then, knowing the shortest periodT _min of the closed trajectories, the long-range behaviour of the ₃ statistic was determined.The authors are greatly indebted to Prof. G. Benettin for many enlightening discussions and to Mr. G. Salmaso for his valuable computational assistance. This work has been partially supported by the Ministero dell'Università e della Ricerca Scientifica e Tecnologica (MURST).     

Internal Bremsstrahlung accompanying non-unique second-forbiddenβ-decay of36CL

The inner Bremsstrahlung spectrum (I.B.) associated wih the non-unique second forbidden-transition of³⁶Cl was measured using a single channel NaI (Tl) scintillation spectrometer. After making all the necessary corrections, the experimental results were compared with the corresponding theoretical distributions due to the KUB, Lewis and Ford, Nilsson, Ford and Martin and Chang and Falkoff. Also a comparison with those calculated according to Nilsson theory after applying the shape correction factor (M. KUB) was done. The measured spectrum is found to show fairly good agreement with M. KUB theory and its found to deviate therafter from all five theories.The authors would like to thank Prof. Dr. M. El-Nadi and Prof. Dr. O.E. Badawy for their suggestions, interest and encouragement.     

Pion production in nuclear collisions

The production of pions in nuclear collisions is analyzed in terms of a microscopic reaction model, where the free energy of the entrance channel is transferred to the final channel through the coupling of the relative motion to the internal excitation of N^*-resonances. Such a model allows quite naturally for a consistent analysis of the exclusive and the inclusive production of pions. It turns out that the pionic fusion cross section is determined predominantly by the spectroscopic parentage between the initial target projectile combination and the final nucleus, whereas the inclusive part is dominated by the energy dependence of the phase space factor, i.e. by the number of the degrees of freedom which are relevant in a given kinematical situation. This model is applied to the analysis of available experimental data from threshold to the (1232)-region. A consistent analysis of both the inclusive and the exclusive part of the pion spectrum is presented.Dedicated to Prof. Dr. P. Kienle on the occasion of his 60th birthday     

In-beam magnetization measurements of thin Fe foils and simultaneous observation of the transient magnetic field at Pd ions

The well established phenomenon of heavy ion beam induced attenuations of transient magnetic fields (TF) was studied by measuring the in-beam magnetization of bombarded Fe foils employing the magneto-optical Kerr-effect. Whereas the macroscopic magnetization did not show any deterioration, the simultaneously measured TF of recoiling¹⁰⁸Pd(2⁺) ions was found to be substantially attenuated.Dedicated to Prof. Dr. P. Kienle on the occasion of his 60th birthday     

Sensitivity of cross section andT 20 to secondary interactions in the reaction indp → ppn at medium energies

Secondary effects in deuteron breakup reactions are reexamined for the process¹ H(d, p) pn with a proton detected at 0° and for the process¹ H (d, pp)n with two fast forward moving protons fixed at the beam line. Sensitivity of the cross section and the tensor asymmetryT ₂₀ to the double-scattering and final-state-interaction corrections is demonstrated. The nonrelativistic method used here incorporates both the energy-conserving and the principal-value part of the free nucleon propagator. The calculations are compared with the inclusive experimental data¹ H(d, p)X at the 1.25 and 2.1 GeV deuteron kinetic energy.The author would like to express his thanks to Prof. B. Tecoult for valuable ideas stimulating this work and Yu.Panebratsev and A. Litvinenko for many helpful discussions. For ideas and advice concerning Sect. 4, I thank to G. Lykasov and S. Shimansky.     

Neutrino oscillations in the sun and the205Tl solar neutrino experiment

Neutrino induced transition rates from²⁰⁵Tl to excited states in²⁰⁵Pb were calculated for neutrino fluxes from the different hydrogen burning reactions in the sun. Suppression factors for electron neutrinos due to flavor oscillations in the sun were obtained. The influence of neutrino oscillations on the neutrino capture rate of²⁰⁵Tl in dependence of the mixing angle and neutrino mass difference is discussed.Dedicated to Prof. Dr. P. Kienle on the occasion of his 60th birthday     

On the role of theΔ -isobar in deep inelastic scattering on the deuteron

The role of the nuclear structure effects, viz. the boundness of nucleons and-isobar components, in the deep inelastic scattering of leptons on the deuteron is considered. It is shown that small admixture of the-isobar configurations to the deuteron wave function may lead to significant effects in the spin structure functions of the deuteronb ₁ ^D andg ₁ ^D (x): up to 4% in g ₁ ^D (x) dx and up to 10% ing ₁ ^D (x) at smallx.One of the authors (A.U.) thanks Prof. F.C. Khanna for helpful discussions and for kind offering the information used in our calculations.     

Kronecker product decomposition for Poincaré-like groups I. A general constructive method

For Poincaré-like groupsW=T×G, i.e. such Type I-groups which are semidirect products of a regularity embedded abelian normal subgroupT with a locally compact groupG, the problem of the Kronecker product decomposition has been solved, in the framework of induced representations theory, up to a reduction of little group representations. For practical applications some computational hints are given.The autors would like to thank Prof. H.Boseck, Dr. J.Niederle and Dr. J.Tolar for helpful and interesting discussions. One of us (Th. G.) would also like to thank Dr. J.Tolar for his kind hospitality during a stay at the Czech Technical University, Prague.     

High spin states in102Ag

High spin states are populated in¹⁰²Ag using the reaction¹⁶O+⁸⁹Y with projectile energies in the energy range 60–80 MeV. Gamma multipolarities are inferred from DCO ratios and coincidence relationships are established among the gamma rays assigned to¹⁰²Ag. A comprehensive level scheme is constructed with four band systems, two of positive parity and the other two of negative parity. The present study extended spins upto 19^– in the main negative parity band. A new band is populated in the present work and is similar to the one observed in¹⁰⁶Ag.The authors wish to thank and record their appreciation to Dr. S.K. Parthasaradhi, VECC, Calcutta for preparing the target used in this experiment. The authors gratefully acknowledge useful discussions with Dr. Rakhesh Popli. The authors record their grateful thanks to Prof. A.P. Patro and Prof. G.K. Mehta, former and present directors of the Nuclear Science Centre, for their interest in this work, helpful discussions and providing excellent facilities. The authors also thank Dr. S.K. Datta of the Nuclear Science Centre for his continued interest and helpful discussions and accelerator staff of N.S.C. for their efficient services in delivering the beam. Grateful thanks are also due to the University Grants Commission for providing financial support.     

Half-life of41Ca

The half-life of⁴¹Ca has been redetermined to be (1.01 ±0.10)×10⁵ yr from the specific activity of a sample of enriched calcium material and its⁴¹Ca concentration. The activity was measured with a Si(Li) detector via the 3.3-keV X rays emitted in the electron capture decay of⁴¹Ca to⁴¹K. The⁴¹Ca concentration was measured by mass spectrometry. Since our result agrees well with the two most recent half-life measurements of Mabuchi et al. (1974), (1.13±0.12)×10⁵ yr, and Klein et al. (1990), (1.03±0.07)×10⁵ yr, we recommend the weighted mean of these three measurements, t_1/2=(1.04±0.05)×10⁵ yr, as the most accurate value of the half-life of⁴¹Ca.Dedicated to Prof. Dr. P. Kienle on the occasion of his 60th birthday     

Spectroscopic studies of real space indirect symmetric GaAs/AlAs short period superlattices

The band structure and the optical transitions of symmetric ultra-short period (GaAs) _m /(AlAs) _n superlattices (n=m is the number of monolayers) have been studied using different spectroscopic techniques, namely photoacoustic spectroscopy, reflectivity and luminescence, photoluminescence excitation and high excitation intensity time-resolved luminescence. Direct observation of the transition from type I to type II energy band alignment is reported for superlattices whose configuration consists of more than 12 monolayers (i.e. m=n>12). The radiative recombination processes associated with the real space indirect transitions have been investigated as a function of the density of photogenerated electron-hole pairs, revealing an unusual density-dependent behaviour. A tentative interpretation in terms of a condensed electron-hole state at the indirect gap is given, which accounts for the long decay time of the type II luminescence at high excitation rate.