新同位素175Er

简介首次合成新核素１７5Ｅｒ及对其衰变纲图测定的实验方法和实验结果． the synthesis and γ decay scheme of new isotope175Er is reported for the first time.The related experimental process and main results are represented briefly also.     

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.     

229Ra的衰变纲图

用１４ＭｅＶ中子轰击钍靶,通过￣（２３２）Ｔｈ（ｎ,α）￣（２２９）Ｒａ反应产生￣（２２９）Ｒａ,由放射化学分离技术从被照靶物质中分离出￣（２２９）Ｒａ活性;利用γ（Ｘ）谱学方法,首次观测到了￣（２２９）Ｒａ的能量为１４．５、１５．６、１８．８、２１．８、２２．５、４４．０、４７．５、５５．０、６３．０、６９．６、９３．６、９４．１、９８．５、１０２．２、１０４．５、１０６．１、１６１．１和１７１．５ｋｅＶ的１８条新衰变γ射线,并建立了￣（２２９）Ｒａ的部分衰变纲图． The￣(229)Ra has been produced in the￣(232)Th (n,α)￣(229)Ra reaction by 14 Mev neutron irradiation of natural Thorium.The￣(229)Ra activities were separated from irradiated target material by radiochemical separation technique. The 18 new γ rays of !(229)Ra decay with energies of 14. 5, 15. 6, 18. 8, 21. 8, 22. 5, 44. 0, 47. 5, 55. 0, 63. 0, 69. 6, 93. 6, 94. 1,98. 5, 102. 2, 104. 5, 106. 1, 161. 1 and 171. 5 keV were found for the first take by using y (X ) ...     

Ultrahigh Spin Structures in 157,158,159Er

Rotational structures at ultrahigh spin in ^157,158,159 Er have been investigated with the configuration-dependent cranked Nilsson-Strutinsky approach. Configurations of observed bands are assigned and the corresponding deformations are given theoretically. The calculations suggest that one of ultrahigh spin bands in ^158 Er is triaxial highly deformed and the other is normal-deformed, while both ultrahigh spin bands in ^157Er are suggested to be triaxial highly deformed. The possible ultrahigh spin bands in ^159Er are predicted to be triaxial highly deformed and have shape coexistence in the same configuration. The configurations with two neutron holes in the Nose = 4 orbitals and two neutron holes in the h11/2 orbitals in ^159Er are favoured for ultrahigh spin states but unfavoured for band termination, which is similar to ultrahigh spin bands in ^157,15SEr.     

The Decay of 120Ba

¹²⁰Ba was produced by 68MeV ¹⁶O beam bombarding a 2mg/cm² thick ¹⁰⁶Cd target and fluorated in a halium-jet ion source.The decay of on-line mass separated activity ¹²⁰Ba has been studied by γ-X,γ-γ γ-β coincidence measurements.Its halflife was measured to be 24±2s.The total decay energy was extracted to be Q_EC=5.0±0.3MeV.A simple decay scheme has been proposed.     

Decay of 95Ru

1.65h ⁹⁵Ru was produced and studied by y ray spectroscopy of ⁹²Mo(a, n)reaction, 34 of the 130 obversed y rays following ⁹⁵Ru decay are new. According to coincidence relations, 29 new γ rays were flited into level scheme, the placement of 7 γ rays in level scheme were confirmed, 3 new levels were assigned, a modified and expanded decay scheme was proposed.     

Searching Triaxial Superdeformation in 175Hf

A two-dimensional Total Routhian Surface(TRS) calculation is carried out in order to ascertain if there is triaxial superdeformation in ¹⁷⁵Hf. A five quasi-particle configuration is chosen in the calculation. Unfortunately, the TRS minimum does not show up in the total potential energy surface.     

Study of 101 Mo Decay

The decay of ¹⁰¹Mo to levels in ¹⁰¹Tc has been studied using the three-parameter (γ-γ-t) coincidence system of HpGe-HpGe detectors. From the coincidence data, the new decay scheme was constructed. The previously reported 104. 70, 105. 95 and 774. 15 keV γ rays were Observed, and have been assigned to the decay scheme for the first time. A newly observed 1508. 01 keV γ ray has also been assigned to the scheme for the first time. The-tensities of β and the values of log ft to most levels were calculated.     

137Eu衰变的在线测量

使用在线同位素分离器及快带传输系统研究了缺中子稀土核137Eu的衰变性质,测量了A＝137核的γ、X单谱及γ-X、γ-γ符合谱,得到了137Eu核的半衰期为9．8s,并观测到了137Eu的一条能量为209．0keV的衰变γ线． The decay properties of neutron-deficient rare earth nucleus 137Eu have been studied by means of on-line isotope separator combined with rapid tape transport system.The products were produced by 190 MeV 36Ar bombarding on Pd target via natPd (36Ar, pxn)137Eu reactions. γ, X singles and γ-X, γ-γ coincidence spectra of the nuclei with A=137 were measured. The half-life of 137Eu is obtained to be 9. 8 s. A γ-ray with energy of 209. 0 keV for 137Eu was observed.     

MICROSCOPIC ANALYSIS OF THE LOW-LYING EVEN PARITY BANDS IN 168Er

Taking into account the pairing correlation plus the quadrupolequadrupole interaction,the intrinsic properties of the low-lying bands (even parity) and the related E2 transition probabilities in ¹⁶⁸Er were calculated in the frame of Bohr-Mottelson-Nilsson model.The agreement between the calculated and the observed results is satisfactory.Some difficulties encountered in the IBM prediction do not appear in the present calculation.     

First Observation of 131Pm Decay

¹³¹Pm nucleus was produced in the ¹⁰⁶Cd (³²S,3p4n) ¹³¹Pm reaction. Theproducts were transported by helium jet and tape system, and X,γ single spectra and X-γ,γ-γ coincidence spectra were measured. The half-life of ¹³¹Pm has beendetermined to be (6.3±0.8)s. A partial decay scheme of ¹³¹Pm is proposed.     

A New Level Scheme of 127I

Study of in beam γ ray spectroscopy of ¹²⁷I has been performed using ¹²⁴Sn(⁷Li, 4n)¹²⁷I reaction at 32 MeV beam energy. A new level scheme of ¹²⁷I has been established including 25 new levels and 52 new γ transitions. Negative parity levels based on 11/2^－ π h_11/2 particle state have been observed up to (35/2^－) extending our knowledge of decoupled structures to the heavier iodine isotope. Two ΔI=2 yrast positive-parity levels have been proposed to be associated mainly with the πg_7/2 configuration due to observations of several strong inter band transitions. Two weakly populated ΔI=2 positive parity levels and a high-lying ΔI=1 cascade have been newly identified and tentatively assigned as πd_5/2 one-quasiparticle and three quasiparticle bands, respectively.     

High-Spin Level Scheme of Odd-odd 142Pm

The level structure of doubly odd nucleus ¹⁴²Pm has been studied via the ¹²⁸Te(¹⁹F,5nγ)¹⁴²Pm reaction in the energy region from 75 to 95MeV. In-beam γ rays were measureed including the excited function, γ-ray singles and γ-γ coincidences in experiment. The level scheme of ¹⁴²Pm has been extended up to excitation energy of 7030.0keV including 25 new γ rays and 13 new levels. Based on the measured γ-ray anisotropies, the level spins in ¹⁴²Pm have been suggested.     

A Limit of Neutrinoless Double Beta Decay of 48Ca

A search for the neutrinoless double beta decay of ⁴⁸Ca is carried out in a coal mine which is located 512m underground near Beijing.Large scintillation crystals of natural CaF₂ were used as both the detector and the double beta decay source.Result obtained after a total of 7588.5 hours of data taking gives 1.1×10²² years (68%C.L.) as the lower limit of the half-life of the neutrinoless double beta decay of ⁶⁸Ca.     

New Gamma Rays from the Neutron-Rich Isotope 189W Decay

The natural Osmium powder was irradiated with fast neutrons.After the chemical separation,the characteristic gamma ray spectra and the time-sequential spectra in the W fraction were measured.11 new gamma lines os ¹⁸⁹W unknown previously were found.     

A New High-Spin Level Scheme of 128I

High-spin states in the beam energies. A new and 72 γ transitions odd-odd nucleus ^128I are investigated via the ^124 Sn（^7 Li,3n）^128 I reaction at 28 and 32 Me V level scheme of 12sI is established up to high-spin states at I^π = 16, including 48 levels The present level scheme is largely different from the one in a recent publication due to identification of several doublet and triplet γ transitions and their proper placements in the level scheme. The high-spin level structure exhibits no obvious collective properties and is possibly associated with two and multi-quasiparticle configurations.     

High-Spin Level Scheme of Odd-Odd 140Pr Nucleus

High spin level structure of doubly odd nucleus ¹⁴⁰Pr has been investigated using in beam γ spectroscopy techniques by means of the ¹³⁰Te(¹⁴N,4n)¹⁴⁰Pr reaction at beam energy of 58MeV.γ-ray excitation functions,γ-ray singles and γ-γ-t coincidences were measured experimentally.The level scheme of ¹⁴⁰Pr,including 27 new levels and 42 new γ-rays,was established for the first time up to 4717.3keV in excitation energy.Based on the measured γ-ray anisotropies,spin values were suggested to the levels in ¹⁴⁰Pr.Several quasiparticle configurations are discussed on the basis of systematics in the neighboring odd odd nuclei,and interpreted qualitatively.     

Level Scheme of High-Spin States in 145Tb

High-spin states of ¹⁴³Tb have been studied via the ¹¹⁸Sn(³²S,1p4n)¹⁴⁵Tb reaction by means of in-beam γ-ray spectroscopy. Measurements of γ-ray excitation functions and γ-γ-t coincidences were performed with 12 BGO(AC)HPGe detectors. A level scheme for ¹⁴⁵Tb including 41 γ-rays which come from the deexcitations of the 24 levels, has been established for the first time based on an analysis of the γ-ray excitation functions, γ-γ coincidence relationships, intensity balances and cross-over transitions. The spins for most of the levels in the scheme are assigned according to the results of the measured γ-ray anisotropies. Considering the structure similarity between ¹⁴³Eu and ¹⁴⁵Tb, the low-lying levels in 145Tb are interpreted by coupling a h_9/2 proton to the excited states in ¹⁴⁴Gd core.     

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.     

Clarification of Confusion in Level Scheme of 124Cs

Low-lying and high-spin states of ^124 Cs are studied through the ^116 Sn（^11 B,3n）^124 Cs reaction at a beam energy of 45 MeV. Several new linking transitions are observed, including three transitions between the yrast and πh11/2 vd3/2 bands and two transitions between the yrast and πh11/2 v（d5/2, g7/2） bands. These transitions fix the excitation energy of the yrast band and its decay path, and confirm the existence of eight E1 finking transitions between the yrast and πh11/2 v（d5/2, 97/2） bands observed before. These E1 linking transitions infer the oetupole correlation in ^124Cs. The decay paths of the yrast band are investigated, and discrepancies in the level scheme of ^124Cs in the latest two studies are clarified. The reason for the discrepancies is discussed. A new decoupled band is established and temporarily assigned as the unfavored signature partner of πh11/2 vd3/2 configuration.