EFFECT OF MULTIPOLE VIBRATION ON M1 TRANSITION OF 1+ STATES IN 208Pb

In this paper, the generate coordinator method (GCM) is applied to study the effect of multipole vibration on M1 transition of 1⁺ states in ²⁰⁸Pb. The calculation shows that coupling between 3^－ collective state and (1p1h) gives much more effect than the coupling effect of 2⁺ state with (1p1h).     

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.     

New Neutron-Rich Isotope 208Hg

The new neutron-rich isotope ²⁰⁸Hg has been identified for the first time from the reaction products in fully-stopping thick ^nat.Pb target bombarded by 30MeV/u ¹²C beam provided by the Heavy Ion Research Facility in Lanzhou.Assignment of the nuclide ²⁰⁸Hg was based on the measurements of the deacy γ energy and halflife of its daughter ²⁰⁸Ti,which was grown up with ²⁰⁸Hg β-deacy.The half-life of ²⁰⁸Hg β-deacy was determined to be 42+23－12 min.The average production cross section of ²⁰⁸Hg over the incident energy region from Coulomb barrier to 30MeV/u is found to be 1.1±0.5μb.     

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 SHAPE ISOMER 240mPu

By means of an annular mica detector, the half-life and excitation function had been measured for the shape isomer ^240mPu produced in the reaction ²³⁸U （α, 2n）. A value of 3.5±0.5 ns was obtained for the half-life of ^240mPu. The shape isomer excitation energy Bi was found to be 3.2±0.5 MeV.     

INTERACTING BOSON MODEL FOR EVEN-EVEN NUCLEI POSSESSED OF 1+ AND 3+ BANDS IN THE ROTATIONAL RIGION

On the bases of s, d IBM, octupole states are taken into account and the two-quasiparticle excitation is treated as boson-like in the SU(3) limit. The energy spectra are obtained analytically and the nondegenerated 1⁺ and 3⁺ bands are also reproduced. The calculated spectra of eight nuclei, which possess with 1⁺ or 3⁺ bands in their energy spectra in the rotational rigion, agree with the experimental ones fairly good.     

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.     

Identification of 208Hg

This paper describes in detail the procedure used in identifing the new neutronrich isotope ²⁰⁸Hg and measuring its half-life. The idetification included two-step chemical separations. The first step was the collection of Hg element products from the irradiated target with a high efficiency and good element selectivity, which was realized by means of an off-line melt Ph target device. The second step was to extract periodically the growing T1 element from the collected Hg sample. In the γspectra of the extracted T1 samples a 2614.6keV γ activity with a half-life of 3min was observed, which may only be assigned to the daughter ²⁰⁸T1 of ²⁰⁸Hg β^－ decay.     

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.     

Surface Diffuseness Anomaly in 16O+208Pb Quasi-elastic Scattering at Backward Angle

The quasi-elastic scattering excitation function of the doubly magic ^16O＋^208 Pb system at a backward angle is measured at sub-barrier energies with high precision. The diffuseness parameters extracted from both the singlechannel and the coupled-channels calculations give almost the same value a = 0.76 ± 0.04 fro. The results show that the coupling effect is negligible for the spherical system. The obtained value is smaller than the extracted value from the fusion excitation function, but larger than the value of a -- 0.63 fm, which is from the systematic analysis of elastic scattering data.     

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.     

ON THE CONTRACTION AND DEFORMATION OF DEUTERON CLUSTER IN 6Li

The ground state of ⁶Li is investigated by means of the projected variational method for double well-cluster shell model. The results of the variational calculation show that the root-mean-square radius of d-cluster in the ground state of ⁶Li is smaller than that of free deuteron and as the mean distance between the α-cluster and the d-cluster decreases there are two effects on the d-cluster, namely contraction effect in which the d-cluster contracts first and then makes a bit extension and deformation effect in which the d-cluster makes oblation first and then streteches.It is also demonstrated by the calculation that the repulsive component of the odd sytate of N-N force and the pauli exchange of the nucleons between the clusters play an important role not only on the cluster structure in the ground state of ⁶Li but also on the contraction and the deformation of d-cluster in ⁶Li.     

THE VERTICAL INTEGRATED MOMENTUM SPECTRUM OF THE MUON WITH MOMENTUM LARGER THAN 4 GeV/c AT 3220m ABOVE SEA-LEVEL

At an altitude of 3220 meters above sea level in Yunnan Province, we measured, by using a G-M counter-magnetic spectrometer, the vertical integratted momentum spectrum of the cosmic muon with momentum larger than 4 GeV/c. The spectrum obtained from this experiment is expressed by a power function in the form of I（>p）=Q （p+4）^-1.86±0.06(cm^-2·sr^-1·s^-1), where p is in GeV/c and Q is a constant. We also measured the charge ratio of muon in the 4—23 GeV/c momentum range. The result is N_μ/N_μ-=1.26±0.11. The error in the momentum measurement with spectrometer has been discussed and calculated.     

Cross Section Calculations for Proton-Induced Reaction on 208Pb with Intermediate Energy up to GeV by Using Quantum Molecular Dynamics

The spallation neutron source induced by high energy protron nucleus interaction is an important link for acceralator driven system. The quantum molecular dynamics (QMD) model is applied to analize the high energy proton induced reactions on ²⁰⁸Pb. The QMD simulations of the double differential cross section of ²⁰⁸Pb (p,xn) reactions with incident energies of 590,800 and 1500MeV are in good agreement with the experimental data,and the results of QMD calculations are better than that of HETC and LAHET.     

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.     

SOME CONJECTURES ON THE MASS FORMULA OF CHARGED LEPTONS

In this note we propose that the electromagnetic self energy of lepton may beconnected with quantum number n by（ （δm）/m）=（1/（2π））n^-b ,in which b is a constant.Wefnrther propose that the cut-off value of momentum M is connected with gravitationalconstant κ and fine structure constant α by M=（1/√κ）αe^-1-b.So we obtainthe mass formula of charged leptons M=（1/√κ）α exp{-3/4-b-(1/3α)n^-b}.By using the masses of e^- and μ^- and the value of a as in put,we get the calculatedvalues of κ=（6.67231±0.00026）×10^-8cm³g^-1sec^-2and m_r=（1782.306±0.078）MeVwhich agree very well with experimental values κ=（6.6720±0.0041）×10^-8cm³g^-1sec^-2 and m_τ=(1782_-4⁺³)MeV respectively.The mass of the fourth charged leptonpredicted by the formula should be m=（11725.47±0.51）MeV,which can be checkedby experiments in the near future.We also discuss briefly the proposed formula andthe obtained results.     

Probability Distribution and Entropy of Nonequilibrium State for 208Pb Nuclei Under Different Excited Energies

The probability distribution and the entropy of ²⁰⁸Pb nuclei under different excited energies are calculated.Comparison is made between the probability distributions and the entropies with time for different excited energies.The result shows that our previous calculation is reasonable.     

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.     

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.     

Theoretical Calculations and Analysis of n+208Pb Reaction for Intermediate Energy Neutron

Based on experimental data of total, nonelastic, elastic cross section and elastic scattering angular distributions for n+Pb reactions, a set of neutron optical model potential parameters is obtained in the region of incident neutron energy from 1—300 MeV. The cross sections, angular distributions and energy spectra are calculated and analyzed by optical model, distorted wave Born approximation theory, Hauser-Feshbach theory, exciton model and cascade mechanism inside nuclear. The results indicate that the cross sections can be given for n+ ²⁰⁸Pb reactions which are all in good agreement with experimental data.