Lifetime measurement of the first excited state of 64Ga

The half-life of the first excited state of ⁶⁴Ga has been measured with a pulsed beam technique. The half-life was determined to be T_1/2 = 21.9 - 0.7 7s. The corresponding B(E2) = 13.6 - 0.4 e²fm⁴ shows good agreement with the Weisskopf estimate, i.e., 15.2 e²fm⁴, thereby establishing the 2⁺ assignment to this state and the single particle nature of the 42.89 keV transition.     

The new nuclide230Pu

In the heavy-ion complete fusion reaction²⁰⁸Pb+²⁶Mg at a beam energy of 135 MeV the new nuclide²³⁰Pu was produced. The measuredα-decay energy was found to be E_α=7050±15 keV. The new isotope was identified after in-flight separation with the kinematic separator VASSILISSA, followed by its implantation into a silicon surface-barrier detector and the observation of the genetic relationships of subsequentα-decays. The half-life of²²⁶U was measured more accurately.     

Observation of Heavy Cluster Emission From Radioactive 230U Nuclei

230Pa was produced with the reaction ²³²TH (p, 3n)230Pa in the irradiation powder targets of ThO₂ with 35 MeV Proton beam. Sources of ²³⁰Pa -²³⁰U were prepared by radiochemical method. Using solid-state track registration detectors, two events of ²³⁰U decay with heavy cluster emission have been observed. The preliminary branching ratio to decay comes out to be B=λ_Ne/λ_α=(1.3±1.8)×10^－14.     

Possible evidence for shape isomeric γ-decay in μ− atoms of 238U

A search for the γ-decay of the shape isomer in muonic ²³⁸U excited by radiationless transitions has been performed. Seven delayed transitions in the energy region of 700 to 3200 keV have been observed with a large Ge(Li) detector. Two transitions with E_γ = 2215 and 3131 keV have been attributed to the decay of the shape isomeric state into levels in the first well. The isomeric shift of the second minimum E₁₁ ≈ 600 keV in the presence of the muon and the decrease of the lifetime of the shape isomer to τ = 12 ± 2 ns give arguments in favour of the connection of shape isomerism with large quadrupole deformations.     

Description of the New Nuclide 259Db and Its α-Decay Chain in Relativistic Mean Field Theory

The new nuclide ²⁵⁹Db and its α decay chain are systematically studied in the framework of the relativistic mean field (RMF) theory with NL3 and TM1 effective interactions. The nuclide ²⁵⁹Db and its α-decay daughter nuclei are calculated in a RMF framework with and without the pairing correlation. With the pairing gaps obtained from the RCHB, the deformed RMF+BCS has been carried out for these nuclei. It has been found that the DRMF+BCS well reproduces the data and implies that the new nuclide ²⁵⁹Db and its α decay daughter nuclei are highly deformed. The α-decay energy Q_α for different channel has been given and it seems that the ground state to ground state Q_α values from DRMF+BCS reproduce the data well. Furthermore the single particle levels of the α decay chain are studied carefully and the explanation for the stability is also presented.     

Study on Deformation and Shape Coexistence for 188Pb

The deformation and shape coexistence in ¹⁸⁸Pb have been investigated in terms of the Projected Shell Model. Comparing the experimental data with the calculated results, it is shown that three shape configurations of sphere (Z=82 shell closure), oblate (two particle-two hole in proton h_9/2 orbital) and prolate (multi-particle-hole)coexist each other in the low-lying excited states and the prolate band exhibits a mixture between two kinds of multi-particle-hole configurations, which means that the neutron i_13/2 alignment happens gradually in this case. The mixing is discussed and the mixing coefficients are given. The oblate band structure is predicted and the 2⁺ prolate state is estimated to be in the energy range of 804—80keV.     

Experimental Measurements for the QEC-Value of 183Os-Decay

Activities of ¹⁸³Os were produced by 39MeV α particles bombarding on a natural tungsten target.β⁺ spectrum with coincidence gate set on the strongest 382keV γ-rays of ¹⁸³Os decay was measured.The endpoint energy of the β⁺ spectrum was determined and the Q_EC value of ¹⁸³Os decay was extracted to be 2.24±0.10MeV which is in good agreement with the predicted value 2.30±0.10MeV on the basis of mass systematics.     

g-factors in the ground state and in the γ-bands in 160,162,164Dy

The g-factors of some members of the ground state band and of the 2⁺ state in the %-vibrational band have been measured in ^160,162,164Dy using the Coulomb Excitation Transient Field technique, induced by ⁵⁸Ni projectiles at 230, 210 and 217 MeV, respectively. The g-factors in the ground state band are consistent with a constant value, while that of the 2⁺_% states is about 20% larger in average than those in the ground state band. Results are discussed in the frame of the systematics in this nuclear region.     

A New Heavy Neutron-rich Isotope 238Th

A new nuclide ²³⁸Th has been produced via multinucleon transfer reaction induced by 60MeV/u ¹⁸O ion irradiation of natural uranium. The thorium was radiochemically separated from the mixture of uranium and its reaction products. The activity of thorium was measured by using a HPGe detector and a planar HPGe detector. The ²³⁸Th has been identified for the first time by measuring the growth and decay of the γ-rays from its daughter ²³⁸Pa. The half-life of 238Th was determined to be (9.4±2.0)min. In addition,a new (89.0±0.3)keV γ-ray with T_1/2=(8.9±1.5)min was observed and assigned to ²³⁸Th decay based on the measurement of transition energy and half life.     

Hydrogen doppler spectroscopy using 15N ions

The energy spread of atomic and molecular ion beams from the 4 MV Dynamitron tandem accelerator at the Ruhr-Universität Bochum has been studied and in part minimized. Using the E_R = 6.40 MeV narrow resonance in ¹H(¹⁵N,!%)¹²C with an ¹⁵N energy spread of 4.55 keV, the Doppler broadening for several hydrogen-bearing gases was found to be in good agreement with expectation: e.g. for NH₃ gas a rotational-vibrational Doppler width of 10.41 - 0.25 keV was observed (theory = 10.4 keV). Studies of the vibrational Doppler widths of H-bonds on a Si 𘜄¢ surface were performed using a 4?%-ray detection system together with UHV-chambers for sample preparation, transport, and analysis. The results showed that further improvements in the experimental set-ups are needed for such investigations.     

Identification of New Isotope 238Th

Unreported heavy neutron-rich nuclide ²³⁸Th has been produced via a multinucleon transfer reaction by 60MeVIu ¹⁸0 ions bombardment of natural uranium.Thorium was radiochemically separated from the mixture of uranium and reaction products. ²³⁸Pa as a daughter nucleus of ²³⁸Th has been identified according to the growth and decay of ²³⁸Pa γ rays which has been observed. The half-life of ²³⁸Th was determined to be (9.4 + 2.0) min. At the same time, a new γ ray of (89.0 + 0.3) keV with T_1/2= (8.9 + 1.5)min was found in the γ spectrum gated with the K_α1, X ray of Pa and assigned to ²³⁸Th decay based on the measurements of its transition energy and the half-life.

     

Experimental Study of Resonance f2(1270) in the J/ψ Hadronic Decay

Based on the 2.5 million J/ψ's collected by the BES at BEPC,through the hadronic decay J/ψ→ωf₂(1270),f₂(1270)→π⁺π^－,ω→π⁺π^－π⁰,the properties of the resonance f₂(1270) are studied:its mass,width,and branching ratio.the angular distribution is fitted with maximum likelihood methood,determining its.J^PC=2⁺⁺ and giving in the first time the helicity amplitude ratios of this process as:x=0.99±0.29; y=－0.24±0.17; z₁=0.90±0.57;z₂=0.56±0.22.     

Experimental Study on 22Na(p,γ)23Mg Reaction

The reaction of ²²Na(p,γ)²³Mg has been investigated at the Radioactive Ion Beam Line in Lanzhou(RIBLL) using a radioactive beam ²³Al. The β⁺ delayed proton decay spectrum has been measured with the TOF-ΔE method and zero degree detectors. The half life of ²³Al is determined to be T_1/2=(476±45)ms by using a time scaler combined with the precision pulse generator,which is consistent with the other group's result of (470±30)ms. The known β⁺ delayed protons at E_r=0.216,0.278,0.438,0.479MeV have also observed in the experiment. The resonance strength of isospin analog state (IAS) is calculated. The resonance intensity of IAS is (11.4±6.0)meV. A new energy level of β⁺ delayed proton decay has been identified at E_x=8.916MeV,and their relative intensity also been obtained.     

Calculation and Analysis of IXK/Iγ(343keV)Ratio and Absolute Intensitiy Calculation of Radiation Data for 175Hf Decay

The method of calculating I_XK/I_γ(343keV)ratio and the analysis and the comparision of experimental measurement for ¹⁷⁵Hf decay are introduced.Based on the data analysis,the emission probability of 343 keV γ-ray, P_γ(343keV)=0.869±0.004,is obtained.Absolute intensities of radiation data for ¹⁷⁵Hf decay are calculated and recommended.     

Nanocrystalline growth and diagnostics of TiC and TiB2 hard coatings by pulsed laser deposition

Nanocrystalline coatings of TiC and TiB₂ were grown by pulsed laser deposition on Si(100) and on X155 steel at low substrate temperatures ranging from 40 °C to 650 °C. A pulsed KrF excimer laser was used with the deposition chamber at a base pressure of 10^-6 mbar. The morphology and structure of the films, studied with SEM, XRD, and TEM, showed that nanocrystalline films with a fine morphology of TiC and TiB₂ were deposited with a grain size of 10 nm-70 nm at all substrate temperatures. The growth of the polycrystalline coatings possessed a columnar morphology with a 𘜄¢ preferred orientation. The hardness of the coatings was determined to be 40 GPa and the elastic modulus, 240 GPa. The composition and the kinetics of the plume produced during the pulsed laser deposition of TiC and TiB₂ was studied under film growth conditions. The mass analysis of ions of the ejected material was performed by time-of-flight mass spectroscopy (TOF-MS) and showed the presence of Ti⁺ and C⁺ during TiC ablation and B⁺, B₂⁺, and Ti⁺ during TiB₂ ablation. The kinetic energies (KE) of the ions depended on the laser fluence which was between 0.5 eV and 340 eV. The kinetic energy and the evolution of the plasma was studied with a streak camera. The velocity of the plasma was of the order of 10⁶ cm/sec and was linearly dependent on the energy fluence of the laser. The emission spectroscopy of the plasma plume confirmed the atomic neutral and single excited species of Ti. These results show that coating growth basically occurs by the recombination of the ionic species at the surface of the substrate.     

Resonance strength measurements of the 27Al(p,γ)28Si reaction in the energy range Ep= 0.8–2.0 MeV

An excitation function of the ²⁷Al(p,%)²⁸Si reaction has been measured over the proton beam energy range E_p = 800-2000 keV using a 4? NaI segmented crystal. In the above energy range 47 narrow resonances were measured and their strengths have been deduced. The absolute efficiency of the detection system has been determined for each one of the resonances via Monte-Carlo simulation, taking into account the decay scheme of each resonance. The results of the present work are compared with literature.     

Laser-induced positive ion and neutral atom/molecule emission from single-crystal CaHPO4·2 H2O: The role of electron-beam-induced defects

We examine laser-induced ion and neutral emissions from single-crystal CaHPO₄·2 H₂O (brushite), a wide-band-gap, hydrated inorganic single crystal, with 248-nm excimer laser radiation. Both laser-induced ion and neutral emissions are several orders of magnitude higher following exposure to 2 keV electrons at current densities of 200 7A/cm² and doses of 1 C/cm². In addition to intense Ca⁺ signals, electron-irradiated surfaces yield substantial CaO⁺, PO⁺, and P⁺ signals. As-grown and as-cleaved brushite show only weak neutral O₂ and Ca emissions, whereas electron-irradiated surfaces yield enhanced O₂, Ca, PO, PO₂, and P emissions. Electron irradiation (i) significantly heats the sample, leading to thermal dehydration (CaHPO₄ formation) and pyrolysis (Ca₂P₂O₇ formation) and (ii) chemically reduces the surface via electron stimulated desorption. The thermal effects are accompanied by morphological changes, including recrystallization. Although complex, these changes lead to high defect densities, which are responsible for the dramatic enhancements in the observed laser desorption.     

The decay of 1.4 min173Er

A 1.4 ± 0.1 min activity which is assigned to β^?-decay of ₆₈ ¹⁷³ Er has been produced with 14–15 MeV neutrons through the reaction¹⁷⁶Yb(n, α)¹⁷³Er. Its decay has been studied with Ge(Li) detectors and several (γ)(γ) as well as (γ)(β) coincidence arrangements. Eight gamma rays with energies 94.2, 116.14, 118.6, 122.40, 192.8, 199.2, 800.8 and 895.2 keV were assigned to the decay of¹⁷³Er. The proposed level scheme of the daughter nuclide ₆₉ ¹⁷³ Tm contains levels at 0, 2.5, 118.6, 124.9, 317.7, 411.9 and 1212.8 keV. The 317.7 keV level is an isomeric state with a measured half-life of 10±3 μs. This 10 μs isomer and the 411.9 keV level are thought to be the band head and 9/2^? rotational member of 7/2^? [523] Nilsson state, respectively. The levels at 0, 2.5, 118.6 and 124.9 keV are interpreted as 1/2⁺, 3/2⁺, 5/2⁺ and 7/2⁺ members of the 1/2⁺ [411] band and the level at 1212.8 keV as the 9/2^? [514] Nilsson state. Some systematic considerations and theoretical transition probability calculations are also included.     

Discovery of a very low-lying 0+ state in 98Sr and shape coexistence implication in 98Sr

Using the on-line mass separator OSTIS for studies of short-lived fission products, we found two modes for the β-decay of ⁹⁸Rb with respective half-lives of 96 and 114 ms. The latter decay populates a 0⁺ state in ⁹⁸Sr at the unusually low energy of 215.5 keV, which is by far the lowest 0⁺ excited state observed in even-even nuclei. The half-lives of the 0⁺ and the 2₁⁺ states in ⁹⁸Sr were found to be respectively 25 ns and 4 ns. The transition probabilities, the reduced E0 matrix element and the observed level structure suggest shape coexistence for ⁹⁸Sr: the spheroidal 0₁⁺ ground state shows a rotational band with the 2⁺, 4⁺, (6⁺) levels, whereas the presumably spherical 0₂⁺ excited state may be connected with the 2⁺ level of a vibrational band. A simple model is proposed.     

Theβ-decay of100Y: Discovery of a very low lying 0+ state in100Zr

Theβ-decay of¹⁰⁰Y has been investigated at the gas filled recoil separator JOSEF by means ofγ-ray and conversion electron spectroscopy. Twoβ-decay modes, of half lives 0.94±0.03 s and 0.55±0.15 s, have been observed. Using Xγ-, Xce-, γγ- andγce-coincidences the level scheme of¹⁰⁰Zr has been constructed. An excited 0 ₂ ⁺ state at 331.3 keV has been discovered in this nucleus. Theβ-decay from the 0.55 s decay mode in¹⁰⁰Y shows a strong preference for the ground state compared to the 0 ₂ ⁺ state in¹⁰⁰Zr. The structure of¹⁰⁰Zr and the nature of the 0 ₂ ⁺ level is discussed in the light of the present results.