Isotope Ratios of Light Charged Particles and Temperature in the Reactions 30MeV/u40Ar+112,124Sn

Coincidence measurements between residues and light charged particles (LCPs) have been made for the reactions 30MeV/u 40Ar+^112,124Sn. The LCPs were measured by 11 semi-conduct telescopes from very forward angle to backward angle. The times of flight of the residues were measured by PPACs installed concentrically around the beam at forward angle. The excitation energy of the primary hot nuclei was obtained from the velocity of residues in the frame of incomplete fusion model. The single isotope ratios, as function of observing angle and excitation energy have been studied. The ratio of ³He/⁴He and ⁶Li/⁷Li increases with angle while that of ⁶He/⁴He and ⁸Li/⁷Li decreases. The calculation of statistical theory can not reproduce the curve quantitatively, implying the existence of dynamic effect. Isospin effect of the primary hot nuclei on the single isotopic ratios is demonstrated. However, the temperature extracted from double isotope ratios is target independent.     

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.     

Isotropic Distribution of the Projectile-Like Products in the Reaction 36Ar+124Sn at 35MeV/u

The projectile-like products at 5.3° in the reaction 35MeV/u 36Ar+ 124Sn were inclusively measured with good isotropic identification. With increasing kinetic energy, the average N/Z ratio of the products gradually decreases,approaching to that of the projectile. It is shown from the isospin dependent quantum mechanics(IQMD) that with the increasing of reaction time, the average kinetic energy of the projectile-like products decreases, while the N/Z ratio increases gradually. Moreover, the isotropic composition is obviously dependent on the impact parameter, and the N/Z ratio is becoming smaller with increasing collision centrality.     

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.     

The Angular Distributions of intermediate Mass Fragments Emittsd in 30 MeV/u 40Ar+58,64Ni and 115In Reactions

The angular distributions of intermediate mass fragments with Z=3-19 emitted in 30 MeV/u ⁴⁰Ar+^58,64Ni and ¹¹⁵In reactions over an angular range of 5°—140°have been measured.Exponential distribution function: dσ/dΩ=N·exp(-θ/a) was used tO fit the measured angular distributions.We have extracted the decay factor a that can be connected with the interaction time τ, and the factor N that is related to the intensity of the emission source.The relationships of a(Z) with Z and N(Z) with Z for different reaction systems and different angular ranges have been discussed. The dependence of angular distributions on isospin and the symmetry of reaction system have also been discussed.     

Element Distributions of Intermediate Mass Fragments Emitted in 30 MeV/u 40Ar+58,64Ni and 115In Reactions

The element distribuhons of intermediate mass fragments (IMF) emitted over an angular region of 5°—140° have been measured in the reachons of 30MeV/u ⁴⁰Ar+^58,64Ni and ¹¹⁵In. Within 20°—80° range the IMFs with Z=3-24 were observed. The IMF production cross section changes smoothly with its charge number,and the element distribuhon changes continuously when the IMF charge number increases across the charge number of the projectile. There is no strong dependence of the element distribution on the charge number of the projectile in this angular region.The transition nature of the reaction mechanism in the intermediate energy region and the power law of the IMF element distribution,as well as the dependence of element distributions on the threshold of the detectors were discussed.     

Light Particle and Complex Fragments Emission from 12C Induced Reactions on 58Ni,64Ni at E/A=46.2MeV

Energy spectra of light charged particles and complex fragments emitted in the interaction of 46.2MeV/u ¹²C with different target ⁵⁸Ni,⁶⁴Ni,¹²C,¹⁹⁷Au and ²⁰⁹Bi have been measured by telescopes,consisting of CsI(Tl) and surface barrier detector stacks.These telescopes for light charged particles and complex fragments have good energy resolution and mass identification.The inclusive data have been analysed within a moving source parametrization.The complex fragment yields from different targets have been compared at several angles.The systematic variation of deduced isotope yields ratios with different reaction systems is used to detemine the N/Z degree of freedom equilibration of the system achieved.     

Isospin Effect on the Emission Mechanism of Hot Nuclei in 35MeV/u 40Ar +112Sn/124Sn Reactions

As an extension of radioactive ion beam physics, the research on isospin dependent properties of hot nuclei has increasingly attracted considerable interest. The isospin effect on the decay of hot nuclei in reactions 35MeV/u ⁴⁰Ar+¹¹²Sn/¹²⁴Sn has been investigared. It is concluded that due to Coulomb repulsion and instability, proton-rich hot nuclei probably emit prides such as a with high energy to increase their neutron-proton ratio. Moreover, the decay chain for those particles is seemingly long and the emission Probability is high. Thus, the conventional observations, for instance, the ‘slope temperature’ extracted from energy spectrum, may very appreciably with the measured particles.     

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.     

Origins of Intermediate Mass Fragments for 40Ar+natAg Reaction at 30 MeV/u

The energy spectra of intermediate-mass fragments (IMF) (3≤Z≤16) have been measured from 6° to 110° for ⁴⁰Ar+^natAg reachon at 30 MeV/u. The energy spectra were analyzed by the moving source model. The natUres of the projechle-like source, target-like source and mid-rapidity source as well as the evolution with angle and nuclear charge were discussed. Two intermediate mass fragments, measured by correlation method in forward angles, come from two sources. One comes from projectile-like source, and other one mainly comes from intermediate source respectively.     

Energy Correlations between Fragments and Light Charged Particles in Reaction of 25MeV/u 40Ar+115In

The correlations between the emitted fragments at θ_lab=15°and the light charged particles(LCPs) at the close geometry configuration in the reaction of 25MeV/u ⁴⁰Ar+¹¹⁵In were measured. The energy correlations between fragments (4≤Zf≤14) and the LCPs including proton, deuterium, tritium and a particle as well as the energy spectra of the LCPs were obtained. The result shows the existence of sequential decay mechanism. It is found that the peak position of angular correlation is at the small angles and the most probable correlation angle is at 2°or so; The peak positions of the two components in the energy spectra of LCPs increase gradually with the mass of correlated partner; The lighter primaly products are more easier to be excited and decay to IMFs and the LCPs. In the Sequential decay, the yield of the LCPs with more heavier mass is higher than that of the lighter LCPs. The result reveals that the total correlation yield ratios summed over the fragments of Z_f=4—14 are 1: 1. 3: 1. 78: 7. 57 for proton, deuterium, tritium and a particles, respectively.     

Optical Potential Parameters of Weakly Bound Nuclear System 17F+13C

Elastic scattering angular distributions of the 14^N＋16^O system and the angular distributions of transfer reaction 16^O（14^N,13^C）17^F at ELab=76.2 MeV and 57 MeV have been measured and calculated by means of the exact finiterange distorted-wave Born approximation with the PTOLEMY code. The optical potential parameters for the weakly bound nuclear system 17^F＋13^C have been deduced and applied to analyse the elastic scattering angular distributions of the similar systems 17^F＋12^C and 17^F＋14^N which are taken from literature. The result shows that the transfer reaction with stable projectile and target combination can be used as an alternative method to extract the optical potential parameters for the weakly bound nuclear system.     

The Cross Section Fluctuation of the Isotope Projectile-Like Fragments in the Dissipative Process of Reaction 19F+51V

By using a detection system combining Time-of-Flight(TOF)method with(△E-E)technique,the excitation functions,the dependence of energy coherence widthΓon product mass A and the dependence of Γon the degree of freedom of neutron excess N/Z for some elements and their isotope products in the dissipative process of reaction ¹⁹F+⁵¹V at energies from 102.25MeV to 109.50 MeV(in 250 keV steps)were presented and discussed for the first time.     

First Observation for Isotope 265Bh(Z=107)

New isotope ²⁶⁵Bh(Z=107) was produced in bombardment of an ²⁴³Am target with 135MeV ²⁶Mg ions at HIRFL. Identification was made by observation of correlated α particle decays between the new isotope ²⁶⁵Bh and its ²⁶¹Db and ²⁵⁷Lr daughters with four pairs of detectors. A total of 8 correlated decay events of ²⁶⁵Bh and 4 decay events of ²⁶⁴Bh were identified. ²⁶⁵Bh decays with a 0.94+0.70-0.31s half-life by emission of α particle with an average energy of (9.24±0.05)MeV.     

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.     

Evaporation of Intermediate-Mass Fragments From Hot-Nuclei in Reaction 40Ar+159Tb at 25MeV/u

The inclusive energy spectra of intermediate-mass fragments(IMF)(3≤Z≤9)have been measured in the range from 20°to 155°for ⁴⁰Ar+¹⁵⁹Tb reaction at 25MeV/u.At backward angles,the spectra of IMF show a characteristic of statistic evaporation and can be well fitted by a moving source with same parameters.The obtained source velocity and temperature are in agreement with the corresponding values of hot nuclei produced in an incomplete-fusion process.Therefore,it seems that there IMF are statistically evaporated from a same source.The experimental results have for compared with the predictions of the statistical model using GEMINI code.     

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.     

Investigation of Intermediate Mass Fragments Emitted in the Reaction of 294MeV 20Ne+159Tb

Intermediate mass fragments(2Z≤11) emitted from 294 MeV ²⁰Ne+¹⁵⁹Tb reaction have been measured by △E-E telescope counters at the angle of 10°—150°region.The energy spectra of the fragments at back angle(>90°) have bell shape,and their peaks locate near the Coulomb barrier of exit channel.The analysis of the energy spectra has been done in terms of moving source and indicate that all the fragments are emitted from a common source,the compound nuclei formed in incomplete fusion process.The charge and angular distributions of the fragments originated from the asymmetric binary decay of the formed compound nuclei have been calculated based on statistical GEMINI code,and the results are in well agreement with the experimental data.     

A Three-Body Model of 11Li,14Be and 17B

The nuclei ¹¹Li,¹⁴Be and ¹⁷B are considered as three-body systems composed of the N=2Z core and two outside neutrons.The core-neutron and neutronneutron interactions are assumed to be the attractive exponential potentials.It has been shown that the three-body system can have a bound state although any two constituents of the system cannot have a bound state. The experimental data of the binding energy and extraordinarily large matter root-mean-square radius can be explained in the frame of the three-body model.     

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.