First Experimental Determination of Half-Life for New Nuclide 65Se

By using experimental data obtained from the measurement of beta-delayed proton decay of ⁶⁵Se produced in ⁴⁰Ca(²⁸Si,3n)reaction,the absolute detection efficiency of particle telescope for rotating radioactive source was imitatively calcu-lated.The half-life of ⁶⁵Se was thus accurately determined to be 9.6_-4.1^+5.3 ms.The β-delayed proton energy of ⁶⁵Se was 3.70±0.08MeV.The partial decay scheme of ⁶⁵Se β-delayed proton decay was revised and proposed.     

Measurements of 79Se with AMS based on extracting molecular negative ions

A new method for measuring selenium-79 with AMS, which is based on extracting molecular negative ions, is described in this paper. According to the experimental results, the extraction ion form SeO₂^－ could depress the interference of Bromine-79 as much as 5 order levels, that is to say, the background of ⁷⁹Br can be deducted to ⁷⁹Br/Se≈10^－10. By the way, the chemical form of sample and preparation flow was also developed. Finally, three ⁷⁹Se AMS calibration standard samples with theoretical ⁷⁹Se/Se ratios of 5.06×10^－7, 6.87×10^－8, 5.40×10^－10 were obtained and the method of ⁷⁹Se measurement was set up, which actualized transmission and detection of ⁷⁹Se. By using our Bragg curve detector, the two isobars ⁷⁹Br and ⁷⁹Se could be partly identified to a certain extent and ⁷⁹Se can be identified from ⁷⁹Br about 1 order level. AMS measurements of the three calibration standard samples above were performed and good linearity was obtained. The sensitivity of the measurement is (5.16±1.80)×10^－11.     

THE BAND 2 OF NUCLEI 156Er AND 158Er

The mechanism of the formation of the band 2 in nuclei ¹⁵⁶Er and ¹⁵⁸Er has been discussed in the framwork of VMI model.     

Research on High Spin States in 68Ge,65Ga and 67Ga

The high spin states in ⁶⁸Ge,⁶⁵Ga and ⁶⁷Ga were studied through in-beam gamma-ray spectroscopy experiment.The reaction ⁴⁶Ti(²⁵Mg,xpxn) was used with beam energy 68MeV.In ⁶⁸Ge the new multiplicity of band structures,the crossing transitions among the bands and a new band with possible big diformation were observed.The experiment results agree with a new microscopic model calculation (EXCITED FED VAMPIR).In ⁶⁵Ga and ⁶⁷Ga a few band structures with strong collectivity were observed and the new level schemes were given.     

THE FINE STRUCTURE OF 208Pb 1+ STATES

The energy levels and transition probabilities B（M1） of the ²⁰⁸Pb 1⁺ states are calculated using the matrix diagonalized method in which the （1p 1h） configurations are coupled to collective octupole phonons. Calculated results show that the fine structure of the ²⁰⁸Pb giant magnectic resonance depends rather strongly on the phononparticle coupling constant.     

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.     

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.     

ON THE TRANSFER MECHANISM OF 16O+24Mg AND 20Ne+24Mg ELASTIC SCATTERING

The mechanism of transfering a cluster of nucleons between two colliding nuclei is considered to explain the backward angle oscillatory rise in the differential cross section of the elastic scattering between certain nuclei, such as ¹⁶O+²⁴Mg or ²⁰Ne+²⁴Mg. The nuclear molecular orbit approximation theory is applied. For one-step transfer, if the parameter involved is assumed to be adjustable, the numerical calculations can be made to fit the experimental results naturally.     

A NEW TRANSITION BRANCH OF THE 5.2 SEC ISOMER IN 183W

During the bombardment of 14.8MeV neutron on natural wolfram samples a γ-ray with energy 291.7keV and halflife 5.17±0.03 sec is observed. From the experimental facts it is assumed that in addition to the two well known transition branches from the decay of 5.2 sec isomer in ¹³⁸W there exists another 11/2⁺11/2[615]→5/2^－3/2[512] isomeric (E3) transition. The hindrance factor of this new transition is calculated. It is well cosistent with the general empirical rule of k^－ forbidden isomeric transition.     

ON THE REACTION MECHANISM OF ALPHA TRANSFER REACTION FOR 16O(16O, 12C)20Ne

The oscillatory structure appeared in the differential cross section of the reaction for ¹⁶O(¹⁶O, ¹²C)²⁰Ne may be explained by particle transfer from covalent channel to ionic channel in the nuclear molecular orbital theory.     

New Low-spin Levels in 76Se and Discussion of Its Yrast Band Structure

The decay of bromine–76 was studied using compton–suppressed spectrometer and high–purity ge detectors in singles and coincidence mode, respectively. bromine–76 was produced via two reactions,i. e.,⁷⁵As(α,3n)⁷⁶Br and ⁷⁶Se(p, n)⁷⁶Br.the results of these experiments verified the previously reported levels and gammas of ⁷⁶Se. in addition to the previously described transitions and levels, 39 new γ–rays and 15 new energy levels were found for the first time. spins and parities for new levels are proposed based on the calculated logft values, de–excitation modes of the observed states, and some nuclear reaction experiment results. a new decay scheme of ⁷⁶Br is proposed in the present work. combining with the high–spin states observed by the in–beam γ–ray spectroscopy of a previous decay work, the positive–parity yrast states were compared with the results from calculations in the framework of the projected shell model.     

A MICROSCOPIC STUDY OF THE LOW-LYING LEVELS OF 18O AND 18F WITH THE SKYRME INTERACTION

The low-lying levels of ¹⁸O and ¹⁸F have been calculated using several Skyrme interactions and the many-body folded diagram theory of Kuo, Lee and Ratcliff. Our results obtained with the Skyrme interactions determined by Vautherin and Brink and by Krewald are not in satisfactory agreement with the experimental spectra.     

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.     

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.     

RADIOCHEMICAL INVESTIGATION OF MASS DISTRIBUTIONS IN 12C-INDUCED FISSION OF 209Bi AND 238U

The yields of 15 and 17 fission, products have been obtained by radiochemical determinations in ¹²C-induced fission of ²⁰⁹Bi and ²³⁸U respectively. From these data, the mass distributions of fission fragments are calculated based on three different hypotheses for the charge distribution. The results seem to indicate that the hypothesis of equal charge displacement gives the best fit to the Gaussian distribution for the masses of the fission fragments. By comparison with the mass distributions for ²⁰⁹Bi (¹²C, f), ²³⁸U(¹²C, f) and ¹⁹⁷Au(¹²C, f) in our early measurement, we find that for fission parameter Z²/A>37, the width of the mass distributions increases with Z²/A rapidly.     

Complete and Incomplete Fusion in the Reaction of 65Cu With 16O Ions

The excitation functions,angular distributions and differential range distributions have been measured for target residues from the reaction of ⁶⁵Cu induced by 45—96MeV ¹⁶O ions with radiochemical techniques.A comparison of the experimental data with Monte-Carlo simulations based on the statistcal model of compound nucleus that the heavy residues are produced by the decay of a compound nucleus formed by complete fusion.Incomplete fusion or massive transfer are the main reaction mechnisms leading to production of the residues with mass number close to that of the target.     

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.     

CONTRIBUTION OF THE 2p-1h MULTIPLE SCATTERING CORRELATION TO THE SPECTRA OF 17O AND 15O

Using the method of Green's function and partial summation of multiple scattering,we have investigated in various approximations the contribution of 2p-1h multiple scattering correlaion to the low energy spectrum of ¹⁷O and ¹⁵O,respectively.In our calculation,the nuclear force employed is the paris potential and the energy dependence of G matrices has been taken into account rigorously.The numerical results agree with the experimental data reasonably well.     

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.     

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.