Blocking of coupling to the 0<Subscript>2</Subscript><Superscript>+</Superscript> excitation in <Superscript>154</Superscript>Gd by the [505]11/2<Superscript>-</Superscript> neutron in <Superscript>155</Superscript>Gd

The concept that the first excited 0⁺ states in N = 90 nuclei are not a b \beta -vibration but a second vacuum formed by the combination of the quadrupole pairing force and the low density of oblate orbitals near the Fermi surface is supported by the blocking of this collective mode in ¹⁵⁴Gd from coupling to the [505]11/2^- single-particle quasi-neutron orbital in ¹⁵⁵Gd . The coupling of this orbital to the 2⁺ g \gamma -vibration in ¹⁵⁴Gd is observed since this coupling is not Pauli-blocked.     

A New Fluorescent Chemosensor Detecting Co<Superscript>2+</Superscript> and K<Superscript>+</Superscript> in DMF Buffered Solution

A new fluorescent chemosensor 2-(2-thiophene)imidazo [4,5,f]-1,10-phenanthroline (L) was prepared and characterized. By adding univalent or divalent metal ions such as Na⁺, K⁺, Mg²⁺, Ba²⁺, Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Ag⁺, Zn²⁺, Cd²⁺ and Hg²⁺ ions into the solution of L in DMF under buffered conditions with the working pH ranging from 7.0 to 8.0, we found that L could be used to detect K⁺ ratiometricly and it could also be applied to sense Co²⁺ with the phenomenon of fluorescence quenching of L. While the response behavior of L was not discernibly affected by other examined metal ions.     

Semiclassical description of the <Superscript>6</Superscript>He+<Superscript>12</Superscript>C elastic scattering

The results of the elastic scattering of ⁶He+¹²C systemat E _Lab = 18 MeV by using the barrier and internal wave decomposition of the S-matrix element within the framework of the WKB method are presented. This is the first detailed study for the interaction of the exotic ⁶He nucleus on different stable nuclei by using a semiclassicalmethod. In this paper, we show that in order to obtain the elastic scattering cross section of the ⁶He+¹²C systemat energies close to the Coulomb barrier, it is vitally important to take into account the inner complex turning points in the calculations and the tunneling effects play a crucial role to explain the experimental data. The semiclassical results are compared with the experimental data as well as the quantum-mechanical one.     

Charge distribution studies in the fast-neutron-induced fission of <Superscript>232</Superscript>Th, <Superscript>238</Superscript>U, <Superscript>240</Superscript>Pu and <Superscript>244</Superscript>Cm

Charge distribution studies for heavy-mass fission products were carried out in the fast-neutron-induced fission of ²³²Th, ²³⁸U, ²⁴⁰Pu and ²⁴⁴Cm using radiochemical and gamma-ray spectrometric techniques. The width parameter( σ_Z/σ_A), the most probable charge/mass ( Z _P/A _P), the charge polarization (ΔZ) and the slope of charge polarization [ δ(ΔZ)/δA ^′] as a function of the fragment mass (A ^′) were deduced. The average charge dispersion parameter ( 〈σ_Z〉) and proton odd-even effect ( δ_p) were also obtained for these fissioning systems. The 〈σ_Z〉 and δ_p values in the fissioning systems ²⁴¹Pu ^* and ²⁴⁵Cm ^* were determined for the first time. The δ(ΔZ)/δA ^′ value is also determined for the first time in the fissioning systems ²³⁹U ^* , ²⁴¹Pu ^* and ²⁴⁵Cm ^* . These data along with the literature data for even-Z fissioning systems such as ²³⁰Th ^* , ²³²Th ^* , ²³³U ^* , ²³⁴U ^* , ²³⁶U ^* , ²³⁸U ^* , ²³⁹Pu ^* , ²⁴⁰Pu*, ²⁴²Pu ^* , ²⁴⁶Cm ^* , ²⁵⁰Cf ^* and ²⁵²Cf(SF) are discussed in terms of nuclear structure effect and dynamics of descent from the saddle to the scission point. The role of the excitation energy in low-energy fission is also discussed. Received: 26 July 2002 / Accepted: 3 December 2002 / Published online: 3 April 2003 RID="a" ID="a"Present address: Emeritus Scientist (CSIR) Bhabha Atomic Research Centre, Nuclear Recycle Group, WIP Building, Trombay, Mumbai-400085, India; e-mail: rhiyer@magnum. barc.ernet.in Communicated by D. Schwalm     

<Superscript>4</Superscript>He<Superscript>3</Superscript>H<Superscript>2</Superscript>H three-body model of the <Superscript>9</Superscript>Be nucleus

Within the framework of the single-channel approximation, an {αtd} model of the ⁹ Be nucleus is presented. A comparative analysis of the t ⁶ Li wave functions describing relative motion of bound states constructed in {ααn} and {αtd} cluster representations is carried out on the example of calculations of the ⁹ Be(γ,t₀)⁶ Li process characteristics. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 85–89, January, 2008.     

Extraction of the neutron charge form factor G<Superscript>n</Superscript><Subscript>E</Subscript>(Q<Superscript>2</Superscript>) from the charge form factor of deuteron G<Superscript>d</Superscript><Subscript>C</Subscript>(Q<Superscript>2</Superscript>)

We extract the neutron charge form factor G ⁿ _E(Q ²) from the charge form factor of deuteron G ^d _C(Q ²) obtained from T ₂₀(Q ²) data at 0≤Q ²≤ 1.717 (GeV/c)². The extraction is based on the relativistic impulse approximation in the instant form of the relativistic Hamiltonian dynamics. Our results (12 new points) are compatible with existing values of the neutron charge form factor of other authors. We propose a fit for the whole set (36 points) taking into account the data for the slope of the form factor at Q ² = 0. Received: 26 July 2002 / Accepted: 18 September 2002 / Published online: 4 February 2003 RID="a" ID="a"e-mail: krutov@ssu.samara.ru RID="b" ID="b"e-mail: troitsky@theory.sinp.msu.ru Communicated by V.V. Anisovich     

Studies of multi-nucleon transfer reactions in <Superscript>90</Superscript>Zr(<Superscript>18</Superscript>O,X) and <Superscript>90</Superscript>Zr(<Superscript>16</Superscript>O,X)

Multi-nucleon transfer reactions in ¹⁸O + ⁹⁰Zr and ¹⁶O + ⁹⁰Zr have been studied at an incident energy of 90 MeV. The energy spectra and angular distributions are measured. The data have been analyzed to obtain cross-section dependence on the number of nucleons transferred and on the ground-state Q-values. In the ⁹⁰Zr(¹⁸O, X); X = ¹⁶O, ^17,16,15,14N, ^14,13,12C, ^12,11,10B, ^10,9,7Be and ^7,6Li reactions, 2n and 2n-correlated transfer cross-sections are observed to be enhanced as compared to the ¹⁶O + ⁹⁰Zr reaction. A detailed comparison in the multi-particle stripping and elastic-scattering cross-section between these two systems are made in order to investigate the possible influence of the two valence neutrons in ¹⁸O nucleus. Diffractional model DWBA calculations, based on the direct surface transfer model, have been performed to understand the reaction mechanism of multi-nucleon transfer to continuum.Received: 12 September 2002, Revised: 24 September 2003, Published online: 27 January 2004PACS: 25.70.Hi Transfer reactions - 25.70.Bc Elastic and quasielastic scattering     

Three-body structure of low-lying <Superscript>18</Superscript>Ne states

We investigate to what extent ¹⁸Ne can be descibed as a three-body system made of an inert ¹⁶O core and two protons. We compare to experimental data and occasionally to shell model results. We obtain three-body wave functions with the hyperspherical adiabatic expansion method. We study the spectrum of ¹⁸Ne , the structure of the different states and the predominant transition strengths. Two 0⁺, two 2⁺, and one 4⁺ bound states are found where they are all known experimentally. Also one 3⁺ close to threshold is found and several negative-parity states, 1^-, 3^-, 0^-, 2^-, most of them bound with respect to the ¹⁶O excited 3^- state. The structures are extracted as partial-wave components, as spatial sizes of matter and charge, and as probability distributions. Electromagnetic decay rates are calculated for these states. The dominating decay mode for the bound states is E2 and occasionally also M1 .     

Light-charged-particle emission from hot <Superscript>32</Superscript>S<Superscript>*</Superscript>formed in <Superscript>20</Superscript>Ne + <Superscript>12</Superscript>C reaction

Inclusive energy distributions for light charged particles (p , d , t and have been measured in the ²⁰Ne (158, 170, 180, 200 MeV) + ¹²C reactionsintheangularrange$10^°$ - - $50^°$.Exclusivelight-charged-particleenergydistributionmeasurementswerealsodoneforthesamesystemat158 MeVbombardingenergybyin - planelightchargedparticle - - fragmentcoincidence.Pre - equilibriumcomponentshavebeenseparatedoutfromprotonenergyspectrausingthemovingsourcemodelconsideringtwosources.ThedatahavebeencomparedwiththepredictionsofthestatisticalmodelcodeCASCADE.Ithasbeenobservedthatsignificantdeformationeffectswereneededtobeintroducedinthecompoundnucleusinordertoexplaintheshapeoftheevaporated$d$,$t$energyspectra.Forprotons, evaporatedenergyspectrawereratherinsensitivetonucleardeformation, thoughangulardistributionscouldnotbeexplainedwithoutdeformation.Thedecaysequenceofthehot$³²S$nucleushasbeeninvestigatedthroughexclusivelight - - charged - particlemeasurementsusingthe$²⁰Ne$$(158 MeV) + $¹²C reaction. Information on the sequential decay chain has been extracted through a comparison of the experimental data with the predictions of the statistical model. It is observed from the present analysis that exclusive light-charged-particle data may be used as a powerful tool to probe the decay sequence of hot light compound systems.     

Evaluated Integral Cross Sections of the <Superscript>3</Superscript>H(<Emphasis Type="Italic">t</Emphasis>,2<Emphasis Type="Italic">n</Emphasis>)<Superscript>4</Superscript>He Reaction in the Low-Energy Region Obtained with Regard to Electron Screening

procedure is considered for analyzing ³H(t,2n)⁴He reaction proceeding in a gas environment with regard to electron screening [1–4]. Results from such an analysis are presented. An electron screening potential of 121 eV is obtained. The magnitude of this potential is three times higher than the one given in [5]. Starting with a 100 eV energy of particle interaction the cross sections of ³H(t,2n)⁴He reaction are calculated using the above potential. The reaction rates are calculated using the evaluated cross sections in the lowenergy region. Enhancement factors for cross sections and reaction rates are defined.     

A miniature tunable TEA CO<Subscript>2</Subscript> laser using isotope <Superscript>13</Superscript>C<Superscript>16</Superscript>O<Subscript>2</Subscript> and <Superscript>12</Superscript>C<Superscript>16</Superscript>O<Subscript>2</Subscript>

A miniature tunable TEA CO₂ laser using isotope ¹³C¹⁶O₂ as the active medium is developed to extend the spectral range of CO₂ lasers for further application. The optimization of the energy parameters of the tunable TEA ¹³C¹⁶O₂ laser and the same laser using ¹²C¹⁶O₂ are studied. When a gas mixture (¹³C¹⁶O₂: N₂: He = 1: 1: 3) at a total pressure of 6.4 × 10⁴ Pa is used, the TEA ¹³C¹⁶O₂ laser of a 45-cm³ active volume obtains 51 emission lines in the [00⁰1–10⁰0] and [00⁰1–02⁰0] bands. The maximum pulse energy of the TEA ¹³C¹⁶O₂ laser is about 357 mJ. The same laser using the conventional gas mixture (¹²C¹⁶O₂: N₂: He = 1: 1: 3) at a pressure of 6.66 × 10⁴ Pa is measured to obtain 69 laser emission lines and the maximum pulse energy of laser radiation is about 409 mJ.     

The low-energy dipole structure of <Superscript>232</Superscript>Th , <Superscript>236</Superscript>U and <Superscript>238</Superscript>U actinide nuclei

In this study, I^p = 1⁺\ensuremath I^{\pi} = 1^{+} and I^p = 1^-\ensuremath I^{\pi} = 1^{-} dipole mode excitations are systematically investigated within the rotational and translational + Galilean invariant quasiparticle random-phase approximation for ²³²Th , ²³⁶U , and ²³⁸U actinide nuclei. It is shown that the investigated nuclei reach a B(M1) strength structure, which corresponds to the scissors mode. The calculated mean excitation energies as well as the summed B(M1) value of the scissors mode excitations are consistent with the available experimental data. The results of calculations indicate large differences to the rare-earth nuclei as is the case for the experiment: a doubling of the observed dipole strengths and a shift of the energy centroid to the lower energies by about 800keV. The calculations indicate the presence of a few prominent negative-parity K^p = 1^-\ensuremath K^{\pi} = 1^{-} states in the 2.0-4.0MeV energy interval. The occurrence of the negative-parity dipole states with the rather high B(E1) value less than 4MeV shows the necessity of explicit parity measurements for the correct determination of the scissors mode strength in ²³²Th , ²³⁶U , and ²³⁸U isotopes.     

Effect of high doses of N<Superscript>+</Superscript>, N<Superscript>+</Superscript> + Ni<Superscript>+</Superscript>, and Mo<Superscript>+</Superscript> + W<Superscript>+</Superscript> ions on the physicomechanical properties of TiNi

The surface layer of an equiatomic TiNi alloy, which exhibits the shape memory effect in the martensitic state, is modified with high-dose implantation of 65-keV N⁺ ions (the implantation dose is varied from 10¹⁷ to 10¹⁸ ions/cm²). TiNi samples are implanted by N⁺, Ni⁺-N⁺, and Mo⁺-W⁺ ions at a dose of 10¹⁷–10¹⁸ cm⁻² and studied by Rutherford backscattering, scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction (glancing geometry), and by measuring the nanohardness and the elastic modulus. A Ni⁺ concentration peak is detected between two maxima in the depth profile of the N⁺ ion concentration. X-ray diffraction (glancing geometry) of TiNi samples implanted by Ni⁺ and N⁺ ions shows the formation of the TiNi (B2), TiN, and Ni₃N phases. In the initial state, the elastic modulus of the samples is E = 56 GPa at a hardness of H = 2.13 ± 0.30 GPa (at a depth of 150 nm). After double implantation by Ni⁺-N⁺ and W⁺-Mo⁺ ions, the hardness of the TiNi samples is ∼2.78 ± 0.95 GPa at a depth of 150 nm and 4.95 ± 2.25 GPa at a depth of 50 nm; the elastic modulus is 59 GPa. Annealing of the samples at 550°C leads to an increase in the hardness to 4.44 ± 1.45 GPa and a sharp increase in the elastic modulus to 236 ± 39 GPa. A correlation between the elemental composition, microstructure, shape memory effect, and mechanical properties of the near-surface layer in TiNi is found.     

Interaction of <Superscript>3</Superscript>He<Superscript>2+</Superscript> and Ar<Superscript>6+</Superscript> ions with acetylene,ethylene, and ethane molecules

Time-of-flight mass spectroscopy methods are employed for studying processes occurring during capture of electrons by ³He²⁺ and Ar⁶⁺ multiply charged ions with energy 6z keV (z is the ion charge) from C₂H _n molecules (n = 2, 4, 6) with different multiplicities of C-C bonds. Fragmentation schemes of the molecular ions formed in such processes are established from analysis of correlations of recording times for all fragment ions. The absolute values of the cross sections of capture of an electron and capture with ionization are measured, as well as the cross sections of formation of fragment ions in these processes. The absolute values of total capture cross sections for several electrons are determined.     

Electron impact excitation into the 3p<Superscript>5</Superscript>4p levels from the 3p<Superscript>5</Superscript>4s metastable levels of argon

Electron impact excitation cross sections of argon from the 3p ⁵4s matastable states to the excited states of 3p ⁵4p configuration were calculated by using the fully relativistic distorted wave method, based on the multi-configuration Dirac-Fock (MCDF) theory. The influence of electron correlation effects on cross sections were discussed in detail. For low energy impact, it is found that the electron correlation effects have a large influence on the cross sections and make the cross sections smaller. However, this influence become smaller with the increasing of incident electron energy. The present results are in good agreement with the experiments of Boffard et al. [Phys. Rev. A 59, 2749 (1999)] in most cases.     

Absence of low-temperature anomaly on the melting curve of <Superscript>4</Superscript>He

The melting pressure and pressure in the liquid at a constant density of ultrapure ⁴He (0.3 ppb of ³He impurities) have been measured with an accuracy of about 0.5 μbar in the temperature range from 10 to 320 mK. The measurements show that the anomaly on the melting curve below 80 mK, which was recently observed [I. A. Todoshchenko et al., Phys. Rev. Lett. 97, 165302 (2006)], is entirely due to an anomaly in the elastic modulus of Be-Cu from which our pressure gauge is made. Thus, the melting pressure of ⁴He follows the T ⁴ law due to phonons in the whole temperature range from 10 to 320 mK without any attribute of a supersolid transition. The text was submitted by the authors in English.     

Dynamical decay process of <Superscript>219, 220</Superscript>Ra<Superscript>*</Superscript> formed in <Superscript>10, 11</Superscript>B + <Superscript>209</Superscript>Bi reactions

The excitation functions for both the evaporation residue and fission have been calculated for ¹⁰B + ²⁰⁹Bi and ¹¹B + ²⁰⁹Bi reactions forming compound systems ^{219, 220}Ra^* , using the dynamical cluster-decay model (DCM) with effects of deformations and orientations of the nuclei included in it. In addition to this, the excitation functions for complete fusion (CF) are obtained by summing the fission cross-sections, neutron evaporation and charged particle evaporation residue cross-sections produced through the axn\ensuremath \alpha xn and pxn\ensuremath pxn (x = 2, 3, 4) emission channels for the ²¹⁹Ra system at various incident centre-of-mass energies. Experimentally the CF cross-sections are suppressed and the observed suppression is attributed to the low binding energy of ^{10, 11}B which breaks up into charged fragments. The reported complete fusion (CF) and incomplete fusion (ICF) excitation functions for the ²¹⁹Ra system are found to be nicely fitted by the calculations performed in the framework of DCM, without invoking a significant contribution from quasi-fission. Although DCM has been applied for a number of compound nucleus decay studies in the recent past, the same is being used here in reference to ICF and subsequent decay processes along with the CF process. Interestingly the main contribution to complete fusion cross-section comes from the fission cross-section at higher incident energies, which in DCM is found to consist of an asymmetric fission window, shown to arise due to the deformation and orientation effects of formation and decay fragments.     

Once more about gauge invariance in <Emphasis Type="Italic">ϕ</Emphasis> → <Emphasis Type="Italic">γπ</Emphasis><Superscript>0</Superscript><Emphasis Type="Italic">π</Emphasis><Superscript>0</Superscript>

It is argued that the realization of gauge invariance condition as a consequent of cancellation between the ϕ → γf ₀ → γπ ⁰ π ⁰ resonance contribution and the ϕ → γπ ⁰ π ⁰ background one, suggested by A.V. Anisovich et al., Yad. Fiz. 68, 1614 (2005), is misleading. The text was submitted by the author in English.     

Nuclear quadrupole moments of 5/2<Superscript>-</Superscript> and 9/2<Superscript>-</Superscript> states in <Superscript>169</Superscript>Ta

The nuclear spectroscopic quadrupole moments for the πh_9/25/2^-, 1/2^-[541] and the πh_11/29/2^-, 9/2^-[514] isomeric states in ¹⁶⁹Ta have been measured employing the time differential perturbed angular-distribution technique following the nuclear reaction ¹⁵⁹Tb(¹⁶O, 6nγ)¹⁶⁹Ta at beam energy 104 MeV. The ratio of the intrinsic quadrupole moments has been derived as 1.87(13) from the measured quadrupole precession frequencies of the corresponding states. The model-independent analysis of the equilibrium deformation indicates strong prolate- and oblate-driving nature of the 1/2^-[541] and 9/2^-[514] orbitals in ^169,171Ta isotopes, respectively.     

Growth defect W<Superscript>3+</Superscript>-W<Superscript>2+</Superscript> of CdWO<Subscript>4</Subscript> crystals

CdWO₄ crystals grown by the Czochralski method at the low-temperature gradient were investigated with electron spin resonance (ESR) spectroscopy. ESR spectra did not contain the spectra of impurity ions typical for the CdWO₄ structure, i.e., Fe³⁺, Mn²⁺, and Cr³⁺. At the same time, in the studied crystals a complex ESR spectrum having the hyperfine structure due to two nonequivalent tungsten atoms was observed (W¹⁸³;I=1/2; natural abundance, 14.28%). Angular dependence analysis and simulation of ESR spectra have shown that this novel spectrum is described by a spin-Hamiltonian with the following parameters:D=839 G,E=80 G,g _xx=2.01,g _yy=1.97,g _zz=1.987 and electron spinS=7/2. There is one magnetically nonequivalent position of the center in the crystal structure and the direction ofD _zz andg _zz corresponds to the direction of W_n-W_n+2 (or Cd_n-Cd_n+2) in the crystal structure. Because of the fact that it is in principle impossible to achieve the electron stateS=7/2 for the d-shell of one transition metal ion and taking into account the fact that such electron state is realized for two nonequivalent tungsten atoms, we suppose the defect structure to be the chain W²⁺-M⁺-W³⁺. In the structure of this defect the ion M⁺ is diamagnetic, the ions W²⁺ and W³⁺ have electron spinS=2 andS=3/2, respectively. The necessary condition for such defect to exist is to place this chain of ions in cadmium positions for the charge compensation. the reason for such defects to form is supposed to be the incorporation of M⁺ ions into the CdWO₄ lattice. The presence of W²⁺ and W³⁺ in Cd positions in the defect structure provides the charge compensation and the lowering of the lattice stress.