Extraction of Nuclear Temperature in 27Al+27Al Dissipative Collision

Energy coherence widths of the dissipative products in the collision ²⁷Al+²⁷Al are extracted from measurement of the excitation functions. Then, the nuclear temperature T of the intermediate dinuclear system are determined, and discussed by using a concept of coherence rotation.     

Measurement of Excitation Function and Analysis of StatisticalProperty in 27Al+27Al mssipative Reaction

The angular distribuhon in the range of 0_cm=50°—90° and excitation funchon of the reachon products in heavy ion dissipahve reachon ²⁷Al+²⁷Al were measured, in the incident energy region from 114MeV to 120MeV with 200keV step. The statishcal property of the fluctuation of the excitation funchon in heavy ion dissipative reaction was discussed based on the integration of the macro outgoing channels.     

Analysis of the Energy Autocorrelation Functions in Dissipative Heavy Ion Collision of 27Al+27Al

The excitation functions of the dissipative fragments emitted from the reaction of ²⁷Al+²⁷Al have been measured in the energy region from 114MeV to 127MeV in steps of 200keV. The detection system covered continuous angles from 10° to 57° in laboratory system. The energy autocorrelation functions of the dissipative fragments have been analyzed by using different approaches,especially using the statistical nuclear reaction model with memory. The results indicate that the intermediate dinuclear system formed in the dissipative process is set in a damped coherent nuclear rotation which causes the nonself averaging oscillation structure in the excitation functions and originates from a typical quantum chaotic motion.     

Measurement of Angular Cross Correlation of the Cross Section Fluctuation in Dissipative Collision 27Al+27Al

The excitation function was measured from θ_lab=10.4° to 57.4° in dissipative collision ²⁷Al+²⁷Al with incident energy ranging from 114 to 123 MeV in step of 200 keV. The Angular-cross Correlation Functions (ACFs) of cross section fluctuation within large angle region were obtained through experiment for the first time. It is found that the angular coherent width is at least 40°. It is interesting that the ACFs is not simple bell shape but shows strong asymmetry. The over-all behavior is that ACF varies more quickly for the backward angles. Itis also noticed that the cross section fluctuation in the forward angle region (θ_cm<70°) shows much stronger angular coherence than in the backward angle region (θ_cm>70°). This angular dependence may be attributed to the coherent rotation effect of intermediate dinuclear system.     

QUASI-ELASTIC AND DEEP INELASTIC REACTIONS OF 12C ON 27Al

Quasi-elastic and deep inelastic reactions of 71.5 MeV ¹²C ions on a ²⁷Al target are measured, ΔE-E telescope is used to identify the reaction products. The energy spectra, angular distributions and contour products in the E-θ plane are obtained and discussed.     

RESEARCH OF RELAXATION PROCESS INDUCED BY 80.6MeV 16O ON 27Al

The decreasing coefficients of the angular distributions, the charge distributions and the first and second moments of the charge distributions with variation of TKEL are deduced from the results of the measurement of projectile-like fragments produced by 80.6MeV ¹⁶O on ²⁷Al. The relaxation process of this reaction is analysed, the effects of the potential energy surface on the first and recond moments of charge distributions are discussed.     

STUDY OF DEEP INELASTIC COLLISION 12C+27Al AT ENERGY 61.8MeV

By using ΔE-E telescope and the time of flight detector, the energy spectra of products between ⁶Li and ¹⁶O were measured for the reaction ¹²C+²⁷Al, at 61.8MeV. The contour plots of differential cross section in c.m. system and the angular distributions of emitted fragments were obtained. The calculated values of fully relaxed energies in deep inelastic collistions agree with the experimental values. The mean interaction time of di-nuclear system was estimated as from 1×10^－21s to 1.4×10^－22s     

MEASURMENT OF PROJECTILE-LIKE FRAGMENTS PRODUCED BY 80.6MeV16O ON 27Al

The projectile-like fragments produced by 80.6MeV ¹⁶O on ²⁷Al were measured using the large area position sensitive ionization chamber. The energy spectra, angular distributions, contour plots of d²σ/dΩdE in the E-θ plane of the reaction products from Li to Na and the Z-distribution were obtained. The cross sections of the quasi and deep inelastic scattering were introduced. A brief discussion of the experimental results is also given.     

THE MEASUREMENT OF COMPLETE FUSION CROSS-SECTIONS FOR THE REACTIONS 12C+27Al, 12C+209Bi AND 14N+Pb

Mica track detectors were used for the measurement of evaporation residues and fission fragments of compound nuclei formed in ¹²C+²⁷Al, ¹²C+²⁰⁹Bi and ¹⁴N+Pb reactions. The complete fusion cross-sections and excitation functions were then obtained. By using the sharp cut-off model approximation, the values of the critical angular momenta were extracted from the complete fusion cross-sections. The results obtained were compared with the calculations based on current theories for critical angular momentum; they were found to agree within experimental uncertainties.     

Fission Time of the Reaction of 10.6MeV/u 84Kr(27Al,Quasi-fission)in Dynamical Model

The dynamical calculation of quasi-fission reaction induced by 10.6MeV/u ⁸⁴Kr on ²⁷Al is performed using one-body dissipation model.The calculation suggests a fission time larger than 200×10^－22 sec.It is found that the threshold for emergence of quasi-fission in the reactoin system is 8MeV/u.     

Azimuthal Distribution and Azimuthal Correlation of the Particles in 10.6MeV/u 84Kr+27Al Collision

The light charged particle emission in coincidence with fragmemts in 10.6MeV/u ⁸⁴Kr+²⁷Al collision is studied.Emphasis is laid on the characters of two-order anisotropy coefficient of Fourier expansion up to two order from fitting particle azimuthal distribution and particle-particle azimuthal correlation.The derived results prove that particle emission is statistically independent with the same azimuthal distribution in each event.It is found that two-order anisotropic coefficient depends weakly on the fragment mass and increases with increasing emitted particle mass.     

Non-Reproducibility of the Cross Sections of the Products Induced from Dissipative Reaction of 17F+27Al

The differential cross sections of the dissipative products B, C, N, O, F, Ne, Na and Mg induced from the reactions of ¹⁹F+²⁷Al at two incident energies have been measured at the HI-13 tandem accelerator, Beijing. In the case of a fixed beam incident energy 114MeV or 118.75MeV respectively, identical reaction system and the same detection system, 20 target points in steps of 2mm on a 10mm×50mm rectangular Al foil have been bombarded. The experimental results indicate that the probability distribution of the cross sections is much wider than a standard Gaussian distribution. This non-reproducibility of the cross sections can't be interpreted by the statistical property of a finite count rate.     

Effect of Rotational Degree of Freedom on the Enhanced Prescission Particle Emission in 10.6MeV/u 84Kr+27Al Reaction

Effect of the rotational degree of freedom of In nucleus in three dimension space on prescission particle emission in 10.6MeV/u and 8.5MeV/u ⁸⁴Kr+²⁷Al collisions was studied in the framework of a statistical model. The calculation results show that for the latter incident energy,particle emission is insensitive to the rotational degree of freedom,while for the former one,the incorporation of this factor leads to the reduction of the extracted fission delay time from 20×10^－21s to 7.5×10^－21s,indicating the existence of this effect. The result also demonstrates that this effect is unable to completely account for the experimental data. In addition,the effect of rotational degree of freedom on particle evaporation prior to scission was found to depend on the excitation energy.     

Angular and Z Distributions of the Fragments at Forward and Intermediate Angles in the Reaction of 25MeV/u 40Ar+115In,58Ni,27Al

The angular & Z distributions of foe fragments emitted in the forward and intermediary angles are measured at the reaction of 25 MeV/u ⁴⁰Ar+¹¹⁵In,⁵⁸Ni,²⁷Al. Their characteristics are investigated based on the model of Modified Qantum Molecular Dynamics (MQMD). Generally, the theoretical calculations are in good agreement with the experiment data. But in the forward angles the yield of the fragments is underestimated by MQMD model while in the case of the intermediate angle region, the calculation is higher than the experiment data in some degree for the fragments whose charge numbers are in the vicinity of the proiectile. The angular & charge distributions of the fragments are also compared with the statistical model of GEMINI. The results turn out to be that a small proportion of the statistical evaporation component exists in the forward angles while in the intermediate angle region, this component increases to some extent. However, its ratio is still small. It is found that the equilibrium evaporation component decreases gradually when the Z of the fragments becomes smaller.     

STUDY OF THE DEEP INELASTIC SCATTERING OF 12C ON 27AI

The deep inelastic scattering of 71.5 ¹²C ions on a ²⁷Al target was measured.ΔE-E telescope was used to identify the reaction products.The contour plots in the E-θ plane for the measured cross sections in the C.M.S.for B and Be show the generalfeatures of quasi-elastic scattering at grazing angles and the deep inelastic scatteringridge extending from smaller angles and flattening at larger ones.Two special featuresmay be worthwhile to mention.First,there are some fine structures near the Q.E.peak.Secondly,the average C.M.kinetic energy of the completely damped part is notequal to the Coulomb energy of the final state.     

CROSS SECTION MEASUREMENTS OF NUCLEAR REACTIONS FOR Ni INDUCED BY 14MeV NEUTRONS

The cross sections of reactions ⁵⁸Ni(n,2n)⁵⁷Ni,⁵⁸Ni(n,p)^58mCo,⁵⁸Ni(n,p)^58gCo and ⁵⁸Ni(n,p)^58m+gCo were measured based on ²⁷Al(n,a) ²⁴Na reaction by activation methods.Incident neutron energies were 14.10MeV and 14.62MeV.A comparison was made between present results and other published data.The cross sections for ^58gCo nuclei formation are given for the first time.     

Optical Potential Parameters for Halo Nucleus System ^6He＋^12C from Transfer Reaction ^11B（^7Li, ^6He）^12C

The optical potential parameters for the halo nucleus system ^6He＋^12C are extracted from fits to the measured angular distributions of ^11B（^7Li, ^6He）12C reaction at energies of 18.3 and 28.3MeV with distorted-wave Born approximation analysis. The characters of the obtained optical potentiM parameters are basically consistent with the results extracted from the fits to the elastic-scattering angular distributions in the literature.     

Angular Distribution of the 12C(6He, 7Li)11B Reaction

Angular distribution of the ¹²C(⁶He,⁷Li)¹¹B transfer reaction is measured with a secondary ⁶He beam of 36.4MeV for the first time. The experimental angular distribution is well reproduced by the distorted-wave Born approximation (DWBA) calculation. The success of the present experiment shows that it is feasible to measure one-nucleon transfer reaction on a light nucleus target with the secondary beam facility of the HI-13 tandem accelerator at China Institute of Atomic Energy (CIAE), Beijing.     

THE CROSS SECTION MEASUREMENT FOR THE 107Ag(n,2n)106mAg REACTION

The cross section for 107Ag(n,2n)^106mAg has been measured by using the activation method relative to the cross section of ²⁷Al(n,α)²⁴Na in the neutron energy range of 13.50—14.73MeV.The values of 469±22,480±22,503±24,538±25,555±25,572±26mb were obtained at the 13.50,13.60,13.90,14.10,14.35,and 14.73MeV neutron energy,respectively.The results are compared with the published data.The neutron energies were determined by activity ratios of Nb and Zr foils.     

SINGLE PROTON TRANSFER REACTION INDUCED BY HEAVY ION 40Ar(11B, 10Be)41K

The angular distribution has been measured for elastic scattering on ⁴⁰Ar with ¹¹B and for the single proton transfer reaction ⁴⁰Ar(¹¹B, ¹⁰Be)⁴¹K at the incident beam energy of 50 MeV. The elastic scattering cross section has been fitted in terms of the optical model. The EFR-DWBA aproach with recoil effect has been used to analyze the differential cross section. The spectroscopic factor was extracted.