摘要:

At the Karlsruhe cyclotron few‐nucleon systems are studied in scattering experiments of polarized fast neutrons on very light nuclei. The continuous energy distribution of the neutron beam from POLKA enables one to measure spin‐dependent observables in the energy range from 15 to 50 Me simultaneously.

ISSN:0094-243X    

DOI:10.1063/1.35009

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Isovector 0+ → 0−(1/2− → 1/2+) transitions have been studied by the charge‐exchange (p,n) reactions on13,14C and16O at Ep=35 MeV by means of the high‐resolution neutron time‐of‐flight technique. Angular distribution of emitted neutrons were measured covering a wide range of the transfer momentum up to q∼2.2 fm−1DWBA analyses with the M3Y interaction give a reasonable account of the observed cross sections at small angles (&thgr;C.M≲60°), where the tensor force plays a significant role. The enhancement of the &Dgr;J&pgr;=0−(p,n) cross section was observed at large momentum transfer. This evidence may suggest an effect of the pionic correlation in the nuclear medium.

ISSN:0094-243X    

DOI:10.1063/1.35010

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The first spectra from the UC Davis cyclotron’s zero degree facility for (n,p) scattering have been obtained from12C,13C,90Zr, and209Bi at an incident neutron energy of 65 MeV. Cross sections for the ground state, the ∼4.4 MeV and the GDR are extracted for the carbon isotopes. Two broad resonances in209Bi at ∼7.5 MeV and ∼15 MeV and a broad resonance in90Zr at ∼22 MeV are compared with previous work done at Davis away from zero degrees.

ISSN:0094-243X    

DOI:10.1063/1.34984

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The charge exchange reaction40Ca(n,p)40K has been measured at 65.5 MeV. A strong enhancement is observed at energies corresponding to the analog of the40Ca G.D.R. The angular distribution is partially consistent with a &Dgr;L=1 transfer, but at forward angles deviates from it. Comparison with the (3He,t) and (p,n) reaction is presented.

ISSN:0094-243X    

DOI:10.1063/1.34985

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The dynamics of isovector modes in nuclei reveal the role of isospin‐ as well as spin‐isospin degrees of feeedom in nuclear structure. Implications of the giant dipole‐ and isovector monopole oscillations for the equation of state of asymmetric nuclear matter will be discussed. Spin‐isospin vibrations are preferentially excited in nucleon‐nucleus collisions at intermediate energy. A recent theoretical analysis including two particle‐two hole as well as isobar‐hole excitations in an extended RPA‐framework will be presented. The relevance of low energy &bgr;+‐strength experimentally accessible for instance in (n,p)‐reactions will be mentioned in connection with neutrino cooling during collapse of type II supernovae.

ISSN:0094-243X    

DOI:10.1063/1.34986

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A review of the evidence that the ratio of neutron and proton multiple matrix elements for collective vibrations in single‐closed‐shell nuclei differ systematically from N/Z is presented. A theoretical framework is given for understanding the data on the basis of the ideas of core polarization. It follows that nuclear deformation parameters are probe dependent and that analysis of excitations by two different probes such as (p,n’) and (n,n’) can, in principle, give the ratio Mn/Mp. Application is made to first 2+states of open shell nuclei. Trends of Mn/Mpfor higher 2+states are presented. Expected systematics of Mn/Mpratios for giant isoscalar quadrupole transitions are presented.

ISSN:0094-243X    

DOI:10.1063/1.34988

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Elastic and inelastic scattering of neutrons from nuclei can be used to study unique aspects about the nuclear structure of the ground states and transitions to excited states. The strengths of (n,p) Gamow‐Teller type transitions in nuclei with N≳Z are particularly sensitive to correlations in the ground‐state wave functions. The relationship between (n,p) and (p,n) Gamow‐Teller reactions and their relevance to the problem of double beta decay will be discussed. Combined analysis of (n,n’) and (p,p’) reactions to the low‐lying 2+states can be used to separate the isoscalar and isovector components of the transitions. Recent experimental results for nuclei in the sd shell will be compared to the latest theoretical calculations.

ISSN:0094-243X    

DOI:10.1063/1.34989

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The strong coupling between scattering to ground and first excited 2+levels of even A nuclei makes low energy neutron scattering a powerful tool for assessing their collective excitation strengths. Higher even parity excited levels are much less strongly coupled to ground state scattering, and the corresponding transition amplitudes are extracted from neutron scattering with less confidence. The sensitivity with which coupling can be assessed for several levels of nuclei, and the sensitivity to details of nuclear structure, will be examined. At incident energies well above low lying collective excitations, elastic scattering is not sensitive to nuclear structure details. The enhanced sensitivity of elastic scattering to structure properties at lower incident energies will be illustrated for the shape transitional nuclei near A=190. Recent results of microscopic model calculations will also be presented, to illustrate the structure insights which can be obtained with those methods.

ISSN:0094-243X    

DOI:10.1063/1.34991

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

We propose a new method for the systematic analysis of elastic and inelastic scattering data which maximizes the information that can be deduced and quantifies the comparison with theoretical models. Our present application studies the utility of nucleons and pions in the determination of matter distributions for normal parity transitions using pseudodata generated for the first 2+state of18O. The intent of this work is to provide perspective on the role of neutron‐nucleus scattering in these determinations. We conclude that the model dependence of analyses of this type can be reduced by having available both neutrons and protons in the same energy region. Some additional remarks on the sensitivity of neutrons to unnatural parity spin and current distributions are included.

ISSN:0094-243X    

DOI:10.1063/1.34992

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Multiple matrix elements are computed for the O+ → O+2transition in34S. (AIP)

ISSN:0094-243X    

DOI:10.1063/1.34993

出版商:AIP    

年代:1985

数据来源: AIP