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1.
The systematics of-decay modes and radiative widths of highly excited states in28Si has been extended by taking-ray spectra on 60 resonances of the27Al(p,) reaction in the range 1097 keVE p 4492 keV (12643 keVE x 15915 keV) and on the24Mg(,) resonances atE =3355, 3431, 4003 keV (E x =12860, 12925, 13 415 keV). The-decay modes of levels in the sub-resonance region (E x =10–12.5 MeV) were studied with both the27 A1(p, ) reaction and the27 A1(d, n) reaction at Ed=4,5,6 MeV. Information on radiative widths of levels was obtained by measuring the resonance strengthsS =(2I+1) p / for 52 resonances of the27Al(p, ) reaction with an emphasis on prospective T=1 states.  相似文献   

2.
The applicability of the method of summed amplitudes of coinciding pulses to determine radiative strength functions of heavy nuclei by measuring two-step cascade-ray spectra is discussed. Experiments based on thermal neutron capture in136Ba and180Hf were carried out to test this method. The values obtained for the radiative strength functions of a wide range of primary transitions were compared with the predictions of two modifications of the giant dipole resonance model. Some insight into the characteristics of the-decay of compound-states is provided by analyzing the information obtained on the two-step-decay of a number of nuclei in the mass region 137A187.Authors' thanks are due to Mrs. T.F. Drozdova and Dr. M.A. Ali for their help in the preparation of the English version of this paper.  相似文献   

3.
-rays are measured in coincidence with the dissipative complex fragments from the35Cl +64Ni reaction at 7.7 A MeV. Theoretical -ray coincidence spectra are determined through a fitting procedure using the contribution of the excited fragment statistical -decay calculated by means of the CASCADE code. Whereas the expected statistical spectra fit very well the data in the energy regionE =2 to 8 MeV, above this energy another emission mechanism in addition to the statistical decay has to be considered in order to reproduce the experimental spectra. Simulations based on the Vlasov equation suggest that this emission could come from the decay of dipole strength excited in the intermediate dinuclear system.The authors are greatly indebted with A. Boiano, A. Buccheri, M. Cipriano, F. Pagano and R. Rocco for their assistance during the set up of the experimental apparatus. Dr. J. Girard and the technical staff of the CEA/DAPNIA-DPhN are acknowledged for the valuable operation of the accelerator.  相似文献   

4.
The couplings of conventional and hybrid mesons to (real and virtual) and their production amplitudes in M are described in a unified manner. Existing results for heavy quarks are recovered, extensions to light quarks and to virtual couplings are made and phenomenological applications discussed. In particular we discuss relativistic corrections to 0+, 1+, 2+ for both real and virtual photons and offer a resolution to a long standing puzzle in perturbative QCD concerning the helicity structure of 2++. We suggest that the production off 2 (1720) involves gluons in an essential way or that this meson hasJ2.  相似文献   

5.
Low-lying states of theN=50 nucleus87Rb have been investigated in the (, ') reaction measuring- and delayed-rf-coincidences. A half-life ofT 1/2=6(1) ns was obtained for the level at 1578.1 keV. This experimental result confirms the 9/2+ assignment and the proton 1g9/2 single-particle character of this state. Experimental M2 transition strengths in85,87Rb are compared with predictions of the shell model and the particle-core coupling model.This work was partly supported by the Bulgarian National Research Foundation.  相似文献   

6.
In-beam- andn-measurements have for the first time identified excited states in the 72 157 Hf85 nucleus and have established its yrast levels up to 6.5 MeV and I=(51/2). The results of parameter-free 11-particle recoupling calculations in the framework of the shell model for the configurationsh 11 2/8 f 7 2/3 andh 11 2/8 f 7 2/2 h9/2 are in excellent agreement with the observed levels up to 39/2 at 4.758 MeV. A weakly populated 52 ns 29/2+ yrast isomer at 2.876 MeV is assigned as the three-neutron configurationf7/2h9/2i13/2.  相似文献   

7.
8.
9.
The reactione + e - e + e - 00e + e - 6 has been analysed using the full data sample taken with the Crystal Ball detector at the DORIS II storage ring at DESY. The 00 invariant mass spectrum is dominated by the ', for which we determine the radiative width (') to be (4.5±0.3±0.5)keV. Near 1.9 GeV/c2 we observe a second enhancement in the 00 mass distribution. Assuming that these events are created by the production and subsequent decay of a wide resonanceX(1900), we have investigated the decay modes, the invariant mass distributions of the 0 and 00 subsystems and the angular distributions of the final state mesons. We find that the data is best described byJ PC=2. For thisJ P assignment the resonance parameters are (X) BR(X)=(0.95±0.27±0.20) keV tot (X)=(221±92±44)MeV, andM(X)=(1881±32±40) MeV/c2.Deceased  相似文献   

10.
A mini transmission-ray Compton polarimeter was developed for the measurement of the sign of magnetic moments of radioactive nuclei with low-temperature nuclear orientation. The signs of the magnetic moments of the following isotopes were determined:193Os [=+0.7297(16) N];191m Ir [=+6.20(9) N];192Ir [=+1.924(10) N];194Ir [=+0.39(1) N];195m Pt [=–0.605(15) N].Dedicated to Prof. Dr. P. Kienle on the occasion of his 60th birthday  相似文献   

11.
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.  相似文献   

12.
New assignments of quantum numbers have been obtained for more than 50 levels in28Si between 8953 and 15915 keV excitation energy. They are based on the measurement of -ray angular distributions or anisotropies on 29 resonances of the27Al(p, ) reaction and on the24Mg(a, ) resonance atE =3355 keV. A total of 15 high-spin states withI=5–7 has been obtained and the spectrum ofT=1 states has been identified up to 15915 keV excitation energy and a maximum spinI=6.  相似文献   

13.
The emission of high-energy-rays in the deexcitation of hot40Ca and39K nuclei formed in heavy-ion fusion reactions at excitation energyE x 90 MeV has been studied. The high energy-rays were measured in coincidence with evaporation residues or light charged particles. The spectrum from the self-conjugated compound nucleus40Ca shows an appreciable yield suppression in the Giant Dipole Resonance (GDR) energy region with respect to the39K, due to isospin selection rules in the dipole-decay. The spectral line shapes of the spectra are well reproduced by using a statistical code which treats explicitly the isospin quantum number in evaluating level densities and transmission coefficients. The GDR parameters determined from the present coincidence measurements are in good agreement with the systematic in theA 40 mass region at lower bombarding energy based on the analysis of inclusive spectra.We thank M. Caldogno for technical support in the development of evaporation residues detectors. We acknowledge the participation of M. Anghinolfi, P. Corvisiero, M. Taiuti and A. Zucchiatti in the early stages of this work. Thanks are due to M. Kicinska-Habior for providing the isospin-dependent code. Discussions with B. Fornal are also gratefully acknowledged.  相似文献   

14.
77Se has been investigated by the reaction74Ge(,n) at 14 MeV. Gamma singles spectra, gamma angular distributions and gamma-gamma coincidences have been taken. A level scheme has been established, spins and parities have been assigned. States of a rotational band on the 1/2 ground state, a rotational band on the 5/2 249.7 keV state and an anormal band have been identified. Nuclear Reaction 74Ge(,n )E =14 MeV; measuredE ,I ,--Coin.,-ang. distr.77Se deduced levels,J, . Enriched target, Ge (Li).  相似文献   

15.
The values of the angle-integrated cross section for the decay to various low-lying states in39K following the40Ca(,) reaction at a mean photon energy of 60 MeV are reported on, together with the values of the reduced Legendre coefficientsa i . The40Ca(,gp) and40Ca(,n) reactions yield the same angular cross-section values and these agree with the corresponding RPA-calculations.Senior Research Associate NFWO  相似文献   

16.
The total photofission cross section ,F for235U and238U has been measured in the energy range 50E 800 MeV at the 855 MeV Mainz Microtron MAMI using energy and time tagged photons (Glasgow Tagger) and a 4 arrangement of position sensitive fragment detectors. Besides the absolute photofission cross section F , which almost completely exhausts the total photon absorption cross section for these nuclei, fragment mass distributions in this energy domain were determined via time of flight techniques (TOF). The results for the total photofission cross sections ,F normalized to the atomic numberA for both isotopes coincide, and agree in the-resonance region, within the systematic errors, with the socalledUniversal Curve ,T /A of the total photon absorption cross section ,T . At higher energies the cross sections exhibit a smooth behaviour. In particular, it is shown for the first time that there isno resonance-like shape near the D13 resonance (at 710 MeV) as observed for the free proton. This complete suppression of the D13 resonance in complex nuclei is not yet understood on a microscopic level. The fragment mass distributions show a predominantly mass symmetric fission. However, contributions from mass asymmetric fission at some photon energies may give a hint of an increased mass asymmetric fission after the onset of the pion and two pion channels.Excerpt from D26 Supported by the Deutsche Forschungsgemeinschaft, SFB 201 Mainz  相似文献   

17.
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.  相似文献   

18.
The -decay of150La, the heaviest isotope of lanthanum, has been identified by observing -rays from mass separated activities obtained at KUR-ISOL. From the decay curves of 97.0 and 208.7 keV -rays in150Ce and of Ce-K X-ray, the half-life of150La has been determined as 0.51(3) s. This value is in agreement with theoretical predictions from microscopic theory.  相似文献   

19.
Bockhorst  M.  Burbach  G.  Burgwinkel  R.  Empt  J.  Guse  B.  Guse  B.  Haas  K. -M.  Hannappel  J.  Heinloth  K.  Hey  T.  Hoffmann-Rothe  P.  Honscheid  K.  Jahnen  T.  Jakob  H. P.  Jöpen  N.  Jüngst  H.  Kirch  U.  Klein  F. -J.  Kostrewa  D.  Lindemann  L.  Link  J.  Manns  J.  Menze  D.  Merkel  H.  Merkel  R.  Neuerburg  W.  Paul  E.  Plötzke  R.  Schenk  U.  Schmidt  S.  Scholmann  J.  Schütz  P.  Schultz-Coulon  H. -C.  Schweitzer  M.  Schwille  W. J.  Tran  M. -Q.  Umlauf  G.  Vogl  W.  Wedemeyer  R.  Wehnes  F.  Wißkirchen  J.  Wolf  A. 《Zeitschrift fur Physik C Particles and Fields》1994,63(1):37-47
The reactions pK + and pK + 0 have been measured with the multiparticle detector system SAPHIR at ELSA in Bonn. Besides the differential cross sections the polarization and, for the first time, the 0 polarization have been determined in a photon induced reaction. All data are presented as functions of the photon energy (from threshold up to 1.47 GeV) and of the kaon production angle (0°–180°). The polarization of both and 0 is substantial at all energies and varies strongly with the production angle.This work is supported by the Bundesminister für Forschung und Technologie (BMFT), FK 06 BN 621 I  相似文献   

20.
The half-lives of seven levels in105Mo have been determined with high precision at the fission-product separator Josef. The-- triple coincidence method with plastic and BaF2 scintillators was used for a determination of the time between the q feeding of a level of interest and its depopulation. A value of q =0.38 (1) for the deformation parameter has been deduced from the half-lives of the first and second excited states. The results of Particle-Rotor model-calculations with the Nilsson parameters=0.084 and=0.28 support the assignment of the Nilsson orbital [532] 5/2 to the ground state of105Mo.The authors acknowledge with pleasure fruitful discussions with Profs. W.R. Phillips, I. Ragnarsson and O.W.B. Schult.  相似文献   

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