MEASUREMENT OF COMPLETE FUSION CROSS SECTION OF 12C+159Tb,12C+165Ho

Complete fusion cross sections have been measured for ¹²C+¹⁵⁹Tb and ¹²C+¹⁶⁵Ho reactions by using K-X rays of evaporation residues with Si(Li)spectrometer.The half-lives of evaporation residues and its yield distributions as a function of incident energy have also been obtained.The experimental values for the complete fusion cross section were compared with the theoretical ones.     

SYMMETRY OF THE ROTATION+VIBRATION SPECTRA FOR NUCLEAR MOLECULE 12C+12C

The rotation-vibration spectra of nuclear molecule ¹²C+¹²C is chassified by the irreducible representations of group U(5). It is shown that the symmetry of rotation-vibration levels of nuclear molecule ¹²C+¹²C are discribed by means of dynamical symmetry U(5)U(4)O(4)O(3).     

THE MASSIVE TRANSFER IN 12C+197Au REACTION

In this paper, we present energy spectra and angular distributions for the α-par-ticles emitted in the reaction of ¹²C+¹⁹⁷Au at 64 and 67 MeV and for α, Be and B emittedin the reaction at 71.5 MeV. The most-probable energles of the variousproducts emittedin this reaction decrease.with decreasing incident energy. The angular distributions peak near grazing angle.The peak position of the angular distributions shift from--80°to--120°while the projec-tile energy decreases from 71.5 MeV to 64 MeV. These all show the features of the transferreaction. The ⁶Li product also has been measured and the ⁸Be particle emitted from thisreaction was detected at 90°to the beam direction using α-α coincident technique at 71.5MeV. The coross section of the ³Be is only few percent at the same angle.     

Excitation Function for 12C+12C Elastic Scattering

An energy dependent optical potential for ¹²C+¹²C system is established based on the analyses of the angular distributions of the elastic scattering in the energy range of 70-160MeV. This potential can well reproduce the excitation function for 12C+12C elastic scattering in the same energy range.     

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.     

THE MEASUREMENT OF LIGHT PARTICLE EMISSION FROM 12C+159Tb,Ag AND 89Y REACTIONS

The energy spectra and angular distributions of α-particle emitted from ¹²C-induced reactions with ¹⁵⁹Tb, Ag and ⁸⁹Y targets have been measured. Meanwhile the emitted deutron's angular distributions with ¹⁵⁹Tb and ⁸⁹Y targets and proton's with ⁸⁹Y target have been also obtained.
The α-energy spectra associated with mentioned reactions have bell-like shape with probable energy near coulomb barrier. However, the main characteristic of the α-angular distribution for ¹⁵⁹Tb and Ag targets is peaked at or near the grazing angles. For the case of ⁸⁹Y target, α-differential cross-sections monotonically decrease with angles beyond 40º. The angular distributions of potons and deutrons nearly decrease exponentially.
The measured α-angular distributions could be divided into two components, one coming from α-evaporation is isotropic, another is anisotropic. The anisotropic component may be explained incomplete-fusion process in which the cross-section can be reproduced by a "Sum-Rule Model" due to J.Wliczynski.
In order to explain the anisotropic component of emitted α-particle, we propose in complete fusion model with a strong-damped sticking rotation, in which the rotation angles and interaction time of the composite system are also estimated.     

ANALYSIS FOR ENERGY SPECTRA OF LIGHT PARTICLES EMITTED FROM 12C+64Ni REACTION

Some experimental results measured for light emission particles with Z≤2 from ¹²C+⁶⁴Ni reaction at E(¹²C)=69, 56MeV are reported. A comparison between moving source model calculation and proton's spectra have been performed. Extracted parameters of the source with faster velocity are agreement with the systematic values found before. The composite particle energy spectra of α, ³He and D were analyzed by coalescence model.     

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.     

EFR-DWBA ANALYSIS OF SINGLE PROTON TRANSFER REACTION FOR 12C+12C AT THE INCIDENT ENERGY 72.5 MeV

Using the square of W-S potential as the real part of optic potential instead of normal W-S potential, we improve the theoretical calculation for the differential cross sections of elastic scattering and single proton transfer reaction. It turns out that the improved theoretical result fit the data better than before.     

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.     

THE MEASUREMENT OF THE EXCITATION FUNCTIONS OF ISOTOPES OF Fr AND At,PRODUCED IN THE BOMBARDMENT OF 12C ON 209Bi

Excitation functions for Fr and At isotopes produced in ¹²C on ²⁰⁹Bi had been measured in the energy range 60—72 MeV. It was quite obvious that ²¹³Fr and ²¹⁴Fr were formed by the reactions ²⁰⁹Bi (¹²C,4n) ²¹⁷Ac and ²⁰⁹Bi (¹²C,3n) ²¹⁸Ac following the a decay of the Ac isotopes respectively, and ^214mFr was produced probably by compound nucleus evaporation of neutrons and an α particle, i.e. (¹²C, α 3n). ²¹¹At was mainly contributed by a multi-nucleon transfer reaction （e.g. ⁸Be transfer）. The experimental data for neutron evaporation reaction were fitted by the Jackson formula.     

RECOIL STUDY OF RESIDUAL NUCLEI I AND Sb IN THE REACTION INDUCED BY 12C ON 115In

Excitation functions and angular distributions of the residual nuclei I and Sb were measured in the reaction of ¹²C on ¹¹⁵In at energies up to 72MeV using radiochemical techniques. A kinematic analysis of the angular distributions showed probable mechanisms leading to productions of I and Sb isotopes.     

Simulation of 200–400 Me V/u ~(12)C+~(12)C elastic scattering on SHARAQ spectrometer

In order to further obtain the information of three-body force(TBF) from 200–400 Me V/u12C+12C elastic scattering, we plan to perform this experiment on a SHARAQ spectrometer. Based on the experimental condition of the Radioactive Ion Beam Factory(RIBF)-SHARAQ facility, a simulation is given to find a compromise between the better energy and angular resolutions, and higher yield by optimizing the target thickness, beam transport mode, beam intensity and angular step. From the simulation, we found that the beam quality mainly limits the improvements of energy and angular resolutions. A beam tracking system as well as a lateral and angular dispersionmatching technique are adopted to reduce the influence of beam quality. According to the two angular settings of SHARAQ as well as the expected cross sections on the basis of the theoretical model, the energy and angular resolutions, and statistical accuracy are estimated.     

SYMMETRICAL ANALYSIS OF 9Be AND 12C HYPERNUCLEI

By analyzing the experimental data of the hypernuclei, we propose a hypothesisthat the single baryon binding energy satisfies the SU(3) uintary symmetry. By thissuggestion, some experimental facts in this field can be explained and we also proposethe possibility of the existence of excited states of the hyper [1] nuclei. Some propertiesof this [1] hyper-nuclei is also pointed out.     

Relaxation of Isospin Degree of Freedom in the Reactions 36Ar+112,124Sn at 35MeV/u

Isotope ratios,defined as the yield ratio of two isotopes with the same charge,were analyzed as a function of kinetic energy of outgoing particles at 20° in the reactions of ⁴⁰Ar+^112,124Sn and 5°in³⁶Ar+^112,124Sn at incident energy of 35MeV/u. Isotope ratios between the neutron-deficient isotopes and stable isotope increase with kinetic energy,while those between the neutron rich isotopes and stable isotope decrease. This different behavior was observed similar for both ¹¹²Sn and ¹²⁴Sn targets. The isotope ratios show rather obvious target dependence at 20° and little target dependence at 5°. As the outgoing energy getting down,the N/Z ratio of the fragmentation products at 5° diverts gradually from the N/Z ratio of the projectile to that of the system. These observations indicate that the isospin degree of freedom does not reach complete equilibrium in the peripheral or semi-peripheral collision at this bombarding energy.     

A SEMI-CLASSICAL ANALYSIS ON THE REACTION 12C+209Bi AT BOMBARDING ENERGIES SLIGHTLY ABOVE THE COULOMB BARRIER

For reactions induced by light heavy ion such as ¹²C, at bombarding energy slightly above the coulomb barrier, using semi-classical theory, neglecting macroscopic frictional force, the reaction mechnisms are sorted by the orbital angular momentum of the entrance channel from the classical deflection functions fitting elastic scattering. Moreover, inserting a transfer probability factor representing the Q-Window effect into the semi-classical angular distribution formula of Kalinkin and Grabowski, we obtain a formula for the differential cross-section per unit energy interval. The calculated results, including the elastic scattering angular distributions, energy spectrum and angular distributions of emitted α-particles in quasi-elastic process, complete fusion cross-section, fusion-fission cross-sections and the exitation functions of evaporated neutron, agree with the experimental data on the reaction ¹²C+²⁰⁹Bi reported by our Institute.     

Entrance Channel Dependence of the Correlation Function of IMFs in 36Ar+112,124Sn at 35MeV/u

The reduced velocity correlation functions of the Intermediate Mass Fragments (IMFs) were measured in the reactions of ³⁶Ar+^112,124Sn at 35MeV/u. The anti-correlation at small reduced velocities is more pronounced in ³⁶Ar+¹²⁴Sn system than that in ³⁶Ar+¹¹²Sn system. The difference of the correlation functions between the two reactions is mainly contributed by the particle pairs with high momenta. A three-body Coulomb repulsive trajectory code (MENEKA) is employed to calculate the emission time scale of IMFs for the both systems. The time scale is 150fm/c in the ³⁶Ar+¹¹²Sn system and 120fm/c in the ³⁶Ar+¹²⁴Sn system, respectively. A calculation based on an Isospin dependence Quantum Molecular Dynamics code (IQMD) reveals that the emission time spectrum of IMFs is shifted slightly leftwards in ³⁶Ar+¹²⁴Sn compared with that in the ³⁶Ar+¹¹²Sn system, indicating a shorter emission time scale. Correspondingly, the central density of the hot nuclei decreases faster in ³⁶Ar+¹²⁴Sn than in ³⁶Ar+¹¹²Sn.     

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     

氮分子离子N+2和氮原子离子N+与Ne原子碰撞激发的比较

用发射光谱法研究了同种元素氮的分子离子N⁺₂和原子离子N⁺与Ｎｅ原子碰撞产生的激发态，获得了靶激发、入射分子离子的分解激发、入射原子离子的激发以及两种离子与靶之间的电荷转移激发等信息．计算了各发射谱线的发射截面．对两种离子引起的谱线发射截面的差异进行了分析，得出一些初步结论，并对此作了些定性解释     

Isospin Effect on Relative State Population Temperature in the Reactions 40Ar+ 112,124Sn at 30MeV/u

An array of 13 detector telescopes has been used for detecting small-angle particle-particle correlations in the reactions ⁴⁰Ar+^112,124Sn at 30MeV/u. The α-α correlation functions were extracted from two-particle coincident events. A three-body trajectory code MENEKA was used to calculate the background correlation function. The detection efficiency was calculated by using the Monte-Carlo method. After subtracting the background correlation and making the detection efficiency correction, the temperatures of 4.18±0.25 0.21 MeV and 4.10±0.22 0.20MeV are obtained from relative populations of ⁸Be states for the reaction systems with different isospin,⁴⁰Ar+¹¹²Sn and ⁴⁰Ar+¹²⁴Sn, respectively. From the relationship between the state population temperature and outgoing particle energies, it is found that the emission temperature decreases with increase of the particle energies for both studied reaction systems. For the neutron deficient system ⁴⁰Ar+¹¹²Sn the emission temperature is 5.13±0.30 0.26MeV for the lower emitting particle energies and 3.87±0.37 0.29MeV for the higher emitting particle energies. And for the neutron rich system ⁴⁰Ar+¹²⁴Sn the emission temperature is 5.39±0.30 0.26MeV for the lower emitting particle energies and 3.32± 0.28 0.23MeV for the higher emitting particle energies. This kind of isospin dependence is discussed.