Excited states in the doubly closed shell nucleus 50 132 Sn82

New excited states in the nucleus¹³²Sn have been identified fromγγ coincidence measurements. Strong beta feeding to a state at 7,210 keV was established. This level is interpreted as a 6^? state formed after aπg ₉ ^2/?1 →vg ₇ ^2/?1 GTβ ^? transition from the 7^? ground state of¹³²In. The deexcitation of the 7,210 keV state passes through a 4,351 keV state, providing support for a 3^? assignment of this level.     

The doubly closed shell nucleus 13250Sn82

The structure of excited states in ¹³²Sn, fed in the β-decay of ¹³²In, has been investigated. Absolute intensities were deduced from γ-singles measurements. From multi-spectrum analysis of γ-lines the half-life of ¹³²In was determined to be 186 ± 22 ms. A level scheme based on γγ and βγ coincidences is presented. The conversion electron spectrum has been studied and internal conversion coefficients deduced for two low-energy transitions. The total decay energy of ¹³²In was determined, from γ-gated β-spectra, to be Q_β = 13.6 ± 0.4 MeV. A lower limit of 6.968 MeV for the neutron separation energy in ¹³²Sn was deduced from the β-delayed neutron spectrum. The experimental results on the level structure of the doubly closed shell nucleus ¹³²Sn show that the shell model is applicable even far from the valley of stability.     

First observation of low lying states in the doubly odd nucleus132Pr from beta decay of132Nd

Excited states of ¹⁰⁸ Te were populated in the ⁵⁴ Fe + ⁵⁸ Ni (270 MeV) reaction using the NORDBALL detector array equipped with charged-particle and neutron detector systems for reaction channel separation. Gamma rays belonging to the neutron deficient nucleus ¹⁰⁸ Te were identified for the first time. On the basis of γγ-coincidence and angular correlation relations a level scheme was constructed with tentative spin and parity assignments. The structure of the nucleus is discussed in the framework of systematics of heavier Te nuclei.     

The 3− state in the doubly closed shell nucleus 64 146 Gd82

Inbeam γ-ray angular distribution measurements establishI ^π = 3^? for the 1579 keV first excited state in¹⁴⁶Gd.     

Properties of the 3− first excited state in the doubly closed shell nucleus146Gd

Conversion electron measurements confirm the 3^? assignment recently proposed for the 1579 keV first excited state in¹⁴⁶Gd. Fromγγ- ande ^? γ-coincidence data the half life of that state has been determined asT _1/2=1.06±0.12 ns.     

Detailed spectroscopy of doubly-magic 132Sn and its neighbours; Perspective for further studies at PIAFE

Experimental studies at the OSIRIS fission-product mass separator have yielded a wealth of new results on the doubly-magic region near ¹³²Sn. In the following we focus on two aspects of the new results: on the evidence for octupole collectivity of the 3₁⁻ state in ¹³²Sn and on the similarity of the ²⁰⁸Pb and ¹³²Sn regions as evidenced from the modelling of the low excitations in ¹³²Sb. The Stage-I of the PIAFE facility recently proposed at Grenoble will offer exciting possibilities for even more detailed studies of the doubly magic regions near ¹³²Sn and ⁷⁸Ni (the latter for the first time).     

Gamma-ray spectroscopy of the doubly magic nucleus 56Ni

The doubly magic N = Z nucleus ⁵⁶Ni has been investigated with two fusion-evaporation reactions; ⁴⁰Ca(²⁸Si, 3α)⁵⁶Ni at a beam energy of 122MeV and ²⁸Si(³²S, 2p2n)⁵⁶Ni at 130MeV. To detect γ-rays in coincidence with evaporated particles the Ge-detector array Gammasphere was used in conjunction with the charged-particle detector system, Microball and a 1π neutron detector array. Results include a significantly extended level scheme of ⁵⁶Ni, which is compared to large-scale shell model calculations in the fp shell. The experimental and theoretical results agree to a large extent, with one notable exception; the theoretical model fails to predict the proper sequence of the yrast and yrare 8⁺ states.     

The total binding energy of the doubly closed shell nuclide 13250Sn82

Using the OSIRIS facility, mass-separated samples containing ¹³²Sb and ¹³²Sn have been prepared, and β-spectra in coincidence with different γ-gates have been recorded. Total decay energies and mass excesses are deduced for these isotopes. The total binding energy of the doubly closed shell nuclide ₅₀¹³²Sn₈₂, is compared to Hartree-Fock calculations using different sets of parameters of the Skyrme effective interaction. The predictions are 2.4 to 3.8 MeV off. This puts doubts on the reliability of calculations of nuclear properties far off the stability valley carried out with these sets of parameters.     

First observation of the excited states in the doubly odd nucleus118Cs identified throughγ-recoil coincidences

The previously unknown nucleus¹¹⁸Cs has been identified through γ-γ and γ-recoil coincidences using the GASP γ-spectrometer and Recoil Mass Spectrometer. The level scheme constructed on the base of triple γ coincidences shows a collective structure based on the π^?1g_9/2?νh_11/2 configuration.     

Quadrupole moment of the doubly closed shell +1 nucleon nucleus41Sc(Iπ=7/2−)

The nuclear electric quadrupole moment of⁴¹Sc(I^π=7/2⁻) was experimentally determined by use of the NMR detection in which the asymmetric β-ray distribution from spin polarized nuclei was monitored. The magnetic interaction of the state with high external magnetic field and the nuclear quadrupole interaction with the electric field gradient obtained in TiO₂ crystal were studied. The field gradient seen to the implanted⁴¹Sc was measured independently by the high field NMR detection on the stable isotope⁴⁵Sc located in the equivalent⁴¹Sc site with. |Q(⁴¹Sc;I^π=7/2⁻)|=(0.120±0.006) b was determined.     

First observation of the doubly charmed baryon Xi(+)(cc)

We observe a signal for the doubly charmed baryon Xi(+)(cc) in the charged decay mode Xi(+)(cc)-->Lambda(+)(c)K-pi(+) in data from SELEX, the charm hadroproduction experiment at Fermilab. We observe an excess of 15.9 events over an expected background of 6.1+/-0.5 events, a statistical significance of 6.3sigma. The observed mass of this state is 3519+/-1 MeV/c(2). The Gaussian mass width of this state is 3 MeV/c(2), consistent with resolution; its lifetime is less than 33 fs at 90% confidence.     

Electromagnetic moments of the doubly closed shell ±1 nucleon nuclei and on-line nuclear polarization

Electromagnetic moments of doubly closed shell ±1 nucleon nuclei were studied. Recent technical developments of the β-NMR was shown that was applicable for the polarized β emitters. Also, the implication of those new moments were discussed especially on the nuclear interactions and non nucleonic degrees of freedom.     

14O核中子闭壳效应的探讨

在引入了BCS理论的相对论平均场模型框架内,通过系统研究氧同位素偶偶核的单粒子能级间隔、单粒子能级占有概率比、对作用效应和粒子数涨落,比较了¹⁴O,²²O和²⁴O三个核的中子闭壳效应,最后从理论上预言丰质子核¹⁴O有着比丰中子核²²O和²⁴O更强的中子闭壳效应. 关键词： 相对论平均场模型 能级间隔 占有概率 粒子数涨落     

First observation of excited states in the neutron-rich nucleus 138Te

The very neutron-rich nucleus ¹³⁸Te produced in the spontaneous fission of ²⁴⁸Cm has been investigated using the EUROGAM II %-ray multidetector array. The excited states of ¹³⁸Te observed for the first time indicate that the region of ground state deformation beyond the doubly magic nucleus ¹³²Sn has yet not been reached.     

Quadruplet spectroscopy in the region of strong nuclear octupole correlations

Experimental evidence from the spectroscopy of¹⁵⁵Gd and¹⁵³Sm for the theoretically predicted quadruplet band structure, with band parity sequences (+––+) and (–++–), is examined.We wish to thank Dr. R. Piepenbring for illuminating discussions on the differences between octupole correlations in the actinides and in the rare earths. These investigations were supported by the National Science Foundation under contract number PHYS9-06613 with the Florida State University.     

Evidence for the doubly magic structure of123Sn

The half lives of the levels at 4,714 keV and 4,415 keV in¹³²Sn have been determined to (20.2±0.8) ns and (4.0±0.3) ns, respectively. The half life of the 4,415 keV level in connection with the existence of aγ transition from this level into the ground state furnishes evidence for the doubly magic character of this nucleus. The transition probabilities which result from both half lives agree well with the theoretical predictions and, thereby, provide information on the structure of the positive parity states in¹³²Sn.