1998 Vol. 22, No. 9
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The targets of statically deformed nuclei 152Sm and 184W were bombarded by 16O beam and the excitation functions of quasi-elastic and elastic scatterings were measured at the backward angles. The barrier distributions, Dqel(E) and Del(E) have been deduced from these excitation functions and compared with fusion barrier distributions extracted from existing fusion excitation function, spin distribution and the results of the experiments with neighboring isotope targets. The agreement is quite good. The calculatons of the Dqel(E) and Del(E) with ECI79 code have already been porformed. It shows that the static deformation effect of target leads to the asymmetric barrier distributions.
The charged particles and residues were correlatively measured by telescopes and PPACs in the reaction of 40Ar+93Nb at incident energy of 25 MeV/u. Energy spectra of αparticles were fitted by three moving sources and the excitation energy of hot nuclei were determined by the TOF of residues and particle multiplicity. Abstracted temperature was correlated thoroughly and the results show that hot nuclei with excitation energy E/A≈4.3MeV and temperature Tinit≈6.9MeV were formed in the reaction The behavior of nuclear matter in various systems was compared and the difference can be seen in the light and heavy reaction system.
Measured drift velocities using an uniform field drift chamber and multiplication factors obtained with proportional tubes in He-based gas mixtures He+CH4(80/20,70/30) and He+iC4H10 (85/15,80/20,70/30) are reported.The results are good agreement with calculations by Garfield Code. The Saturated drift velocity is Vd≈2.7cm/μs and multiplication factor of M≈104—105 at certain working voltage is manageable in He/CH4(80/20) gas mixture,and it is good candidate of working gas for use of low momentum and high precision measurement in the drift chambers.
Gamma rays, light charged particles and evaporation residues emitted from hot nuclei formed in the 40Ar+93Nb reaction at 25MeV/u have been measured.The initial excitation energies of the hot nuclei can be deduced from the velocity of the incomplete fusion residues by applying a massive transfer model. The integrated γ multiplicity, after bremsstrahlung substraction, is constant as a function of excitation Statistical calculations were performed by using the CASCADE code, and compared with experimental data. The main effects which can lead to the saturation of the GDR γmultiplicity at high excitation energies were discussed. The experimental data can be fitted by assuming a cutoff of γ emission from the resonance above an excitation energy of approximate 250MeV.
Superdeformed rotational bands in 191-192-193-194Hg are analyzed by means of the Uqp(u2) model. An overall and excellent agreement between the calculated and observed spectra Eγ, kinematic moment of inertia J(1) and dynamic moment of inertia J(2), the aligned angular momentum (i=ω(J(1)(191-193-194Hg)-J(1)(192Hg))) is obtained Further more, the nuclear softness in 191-192-193-194Hg are calculated by means of the Uqp (u2) model and drawn into the nuclear. configuration analysis.
A Lower energy duality string model with time dependent metric, torsion, dilaton background field and Liouville potential field is studied in this paper. A classical string cosmological solution in D=3 space-time dimension is obtained. By means of O(2,2) duality transformation, we find that a new cosmological solution containing singular points can be generated.
In this paper, the polarization tensors of H→Zrr at one-loop level are discussed. The constrained equations for the tensors are deduced from the S2 symmetry and guage invariance.
The finite temperature and density effect of vacuum polarization as well as the electromagnetic proptrty of thermal background medium are investigated. The vacuum polarization tensor the electrical permittivity and magnetic permeability are calculated strictly, and the strictly anlytical expression is presented which is applicable to all temperature and various density.
New formulas for the in-medium nucleon-nucleon collision cross section are presented, in which the nuclear matter desity and the incident energy are included. These formulas are used to study the total nuclear reaction cross section based on a Coulomb-modified Glauber model. The calculation can reproduce the experimental results of both stable nuclei and exotic nuclei induced reactions over energy range from 10MeV/nucleon to 1GeV/nucleon.
From the shell model configurations, valence nucleon effective interactions and fermion E2 transition operator, the sdgIBM-1 Hamiltonian and the boson E2 transition operator are microscopically deduced in accordance with an approach which is based on Dyson boson expansion. The spectra and the reduced E2 transition matrix elements are calculated for the even 190─200Pt isotopes. Present theoritical calculations fit experimental data or phenomenological results fairly well.
The necessity and possibility of improving the isotope separator on-line are analyzed. The principals of laser stepwise resonance ionization and laser ion source at ISOL are introduced. The element selectivity of the hot capillary type laser ion source and its influence factors are analyzed in detail. The lasers and laser technique used in the laser ion source are alse described. The laser ion source of the capillary type was tested by the experiments. Its result proved that the laser ion source has an opportunity clement selectivity from 50 to 10000.
In the conceptual design of a dedicated medical proton synchrotron, a ferrite-loaded untuned RF cavity is used. A prototype of cylindrical cavity is made and studied, Within operation frequency region, the prototype matches power source.
Electron Paramagnetic Resonance has been used to investigate the defects produced in silicon by irradiation with 12MeV Ar ions below 50K. Several kinds of defects, which include the neutral 4-vacancy (Si-P3center), amorphous center and etc. are observed in the as-irradiated samples. The Si-P3 center is distributed in the regions where electronic stopping power dominates and is annealed out at about 200℃. Accompanied by the disappearance of the Si-P3 center, the complex vacancy clusters, such as Si-P1 center and Si-A11 center begin to grow. The recrystallization of the isolated amorphous region occurs at 350℃. The radius of the produced amorphous region for low fluence Ar ion irradiated sample is evaluated and it is distributed in the range from 16 to 20A. The results are qualitatively discussed.
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