Single-particle neutron characteristics of Cd isotopes with N of 50 to 82

Experimental data on single-particle neutron energies of Cd isotopes are analyzed within a dispersive optical model. Parameters of the potential are extrapolated to the region of unstable isotopes with a neutron excess. The evolution of calculated single-particle spectra and occupation probabilities of single-particle orbits corresponds to formation of magic features in Cd isotopes with N = 50, 82. The results from calculations agree with the concept that the ¹⁷⁴Cd isotope with N = 126 forms the end of the peninsula at the neutron drip line.     

Decay of neutron-rich Ga isotopes near N = 50 at PARRNe

The PARRNe facility has been used to produce neutron-rich isotopes ^83,84Gaby the ISOL method. Their decay has been studied, and β-γ coincidence and γ-γ coincidence data were collected as a function of time. The first two excited levels in ⁸³Ge and the first excited level in ⁸⁴Ge have been measured for the first time.     

Structure of neutron-rich Ar isotopes beyond N = 28

Results from the gamma-ray spectroscopy of {47,48}Ar exemplifying new limits of sensitivity for characterizing neutron-rich nuclei at energies around the Coulomb barrier are presented. The present results, along with interacting shell model calculations, highlight the role of cross-shell excitations and indicate the presence of a nonaxial deformation in 48Ar.     

New constraints on spin-dependent WIMP-neutron interactions from HDMS with natural Ge and <Superscript>73</Superscript>Ge

In the mixed spin-scalar coupling approach the data from HDMS (Heidelberg Dark Matter Search) experiments performed in the years 1996, 1997, 2001–2003 both with natural Ge and with enriched ⁷³Ge were simultaneously analyzed. This analysis together with a new procedure for background identification and subtraction from the measured ⁷³Ge spectrum allowed us to obtain a significant (about one order of magnitude) improvement for the limits on the WIMP-neutron spin-dependent coupling. As a result, the HDMS experiment is now giving the most sensitive limits on the WIMP-neutron spin coupling for WIMP masses larger than 60–65 GeV/c ². The text was submitted by the authors in English.     

Electromagnetic properties of neutron-rich Ge isotopes

The electric quadrupole moment Q and the magnetic momentp(or the g factor) of low-lying states in even-even nuclei ~(72-80)Ge and odd-mass nuclei ~(75-79) Ge are studied in the framework of the nucleon pair approximation(NPA) of the shell model,assuming the monopole and quadrupole pairing plus quadrupole-quadrupole interaction.HA H.Our calculations reproduce well the experimental values of Q(2_1~+) and g(2_1~+) for ~(72,74,76) Ge,as well as the yrast energy levels of these isotopes.The structure of the 2_1~+ states and the contributions of the proton and neutron components in Q(2_1~+) and g(2_1~+) are discussed in the SD-pair truncated shell-model subspace.The overall trend of Q(2_1~+) and g(2_1~+)as a function of the mass number A,as well as their signs,are found to originate essentially from the proton contribution.The negative value of Q(2_1~+) in ~(72,74)Ge is suggested to be due to the enhanced quadrupole-quadrupole correlation and configuration mixing.     

Properties of rotational excitations in odd mass Dy isotopes

The data on high-spin rotational states in¹⁵⁵Dy,¹⁵⁷Dy,¹⁵⁹Dy and¹⁶¹Dy are discussed within a model where a particle is coupled to a rotor with a variable moment of inertia. In this model there is often a definite improvement in the quality and stability of the fits to levels in the positive-parity band below spin 25/2 when the moment of inertia of the core exhibits a linear dependence on the square of the rotational angular velocity as compared to the situation where a linear dependence onI(I+1) is assumed. In the improved fits the empirical matrix elements of the Coriolis force exhibit a smooth and significant increase with decreasing moment of inertia. The rotational energies above spin 25/2 in the positive-parity band and above 19/2 in the 11/2^? [505] band are understood within the present theoretical model if the moment of inertia increases more rapidly than the linear trend established at lower spin. In the 11/2^? [505] band this increase follows rather closely the behaviour in the even nuclei whereas in the positive-parity band the curves are quite flat even beyond the point where the moment of inertia in the even nuclei exhibits a discontinuous or back-bending behaviour. The significance of this observation is discussed in the light of existing theories on nuclear moments of inertia.     

Phase analysis of <Superscript>4</Superscript>He-<Superscript>4</Superscript>He scattering at energies of 40–50 MeV

A phase analysis of ⁴He-⁴He elastic scattering is performed for energies of 40–50 MeV. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 74–79, June, 2007.     

Band termination in the Z = N odd-odd nuclei <Superscript>46</Superscript>V and <Superscript>50</Superscript>Mn

The configuration-dependent cranked Nilsson-Strutinsky approach has been employed to study the properties and band structures at high spin in the Z = N odd-odd nuclei ⁴⁶V and ⁵⁰Mn. The observed bands are explained and terminating states are confirmed by the calculations. The calculated and observed bands are in good agreement without normalization, especially for terminating states. Possible bands with rotation around the intermediate axis and the effect of γ-deformation on the total energy of several interesting configurations are discussed. Received: 2 April 2002 / Accepted: 27 January 2003 / Published online: 15 April 2003     

Influence of Ge addition on the optical properties of As40Se50Ge10 thin film probed by spectroscopy techniques

The thin films of As₄₀Se₆₀ and As₄₀Se₅₀Ge₁₀ were prepared on glass substrates by thermal evaporation method with thickness 1000 nm. The prepared films were amorphous in nature which was confirmed through X-ray diffraction. The chemical composition and the surface picture were obtained from energy dispersive X-ray analysis and Scanning Electron Microscopy analysis. The transmission data of the two films were collected in the wavelength range 400–1000 nm. The transmission percentage is found to be decreased whereas the absorption coefficient is increased with the Ge addition. The addition of Ge into As₄₀Se₆₀ is found to increase the refractive index and the extinction coefficient of As₄₀Se₅₀Ge₁₀ thin film. The decrease in optical band gap is explained on the basis of increase in density of states and disorderness due to Ge addition. The optical absorption in the film is due to allowed indirect transition, and the homopolar bond density is increased with Ge addition. The Raman shift observed in the two films clearly supports the optical changes due to Ge addition.     

Investigation of neutron deficient nuclei in the region 28<N,Z <50 with the help of heavy ion compound reactions

In-beamγ ray spectroscopy withγ singles spectra,γγ coincidences andγ ray angular distributions has been performed with several target-projectile combinations:^natCa +³²S,^natCa +⁴⁰Ca,⁵⁴Fe +¹⁴N,⁵⁸Ni +¹²C,⁵⁸Ni +¹⁴N,⁶⁶Zn +¹⁶O,⁶⁸Zn +¹⁶O. Level schemes of⁶⁶Ge,⁶⁸Ge,⁶⁹As,⁷⁰Se,⁷⁴Kr,⁸⁰Sr and⁸²Sr have been deduced. The following level energies and spin-parity assignments have been found:⁶⁶Ge: 957.4 keV, 2⁺; 1693.7; 2174.7, (4⁺); 3685.7; 4207.5;⁶⁸Ge: 1015.8, 2⁺; 1777.9, 2⁺; 2267.9, 4⁺; 2428.8, 3(⁺); 2649.1, 3^?; 3582.3, (5^?); 3649.3, (5^?); 3696.2, (6⁺); 3883.3, (6^?); 4054.4, (7^?); 4454.6; 4837.3;⁶⁹As: 98.2; 164.6;789.6;863.2; 1306;2160;2210.4;2831.5;3258.3;3263.5;3991.1;5195.7;⁷⁰Se: 945.4, 2⁺; 1600.9; 2039.4, (4⁺);⁷⁴Kr: 455.7, 2⁺; 1013.5, (4⁺); 1781.5;⁸⁰Sr: 385.4, 2⁺; 980.2, (4⁺); 1763.2, (6⁺);⁸²Sr: 573.4, 2⁺; 1328.5,(4⁺); 2229.6,(6⁺). γ ray activity spectra have been measured after the bombardment of natural Ca with³²S. The half-life of the new isotope⁶⁹Se has been found to be 27±3 sec. Recoil distance Doppler-shift measurements have been performed with the reactions^62,64Ni,⁶⁶zn(¹⁶O, 2n)^{76, 78} Kr,⁸⁰Sr. The following half-lives have been determined:⁷⁶Kr: 423.8 keV, 2⁺, 37±5 psec; 1034.2,4⁺, 5.7±1.6;⁷⁸Kr: 455.3, 2⁺, 25±3; 1120.0, 4⁺, 3.8±1;⁸⁰Sr: 385.4, 2⁺, 44±6. The energy and half-life systematics of the first excited state of even-even nuclei suggest a maximum of nuclear deformation in the region 28≦N, Z≦50 near ₃₈ ⁷⁶ Sr₃₈ or ₄₀ ⁷⁸ Zr₃₈.     

Structure of odd–odd La at high spin

The high spin states in the N=79 odd–odd ¹³⁶La nucleus have been investigated by in-beam γ-spectroscopic techniques following the ¹³⁰Te(¹¹B, 5n)¹³⁶La reaction at E=52 MeV using an array, consisting of eight Compton-suppressed clover germanium detectors. Thirty nine new γ rays have been assigned to ¹³⁶La on the basis of γ ray singles and γγ-coincidence data. The level scheme of ¹³⁶La has been extended above the known 115 ms isomer upto an excitation energy of 4.6 MeV and spin 18. Thirty one new levels have been proposed and spin-parity assignments for most of the newly proposed levels have been made on the basis of the deduced asymmetry ratios and polarisation information for the de-exciting transitions. The observed positive parity yrast band has been compared with the theoretical calculation, done within the framework of particle rotor coupling model (PRM) where the two odd quasi-particles are coupled to an axially symmetric core. The level structure has been discussed in the light of the known systematics of the neighbouring N=79 isotonic nuclei.     

Thermal neutron capture cross-section of <Superscript>76</Superscript>Ge

The thermal neutron capture cross-sections of the ⁷⁶Ge(n,)⁷⁷Ge and the ⁷⁶Ge(n,)^77m Ge reactions have been measured by activating targets of isotopically enriched GeO₂ through cold neutrons. The -decay spectra after the -decay of ⁷⁷Ge and ^77m Ge were measured with HPGe detectors. From these spectra the cross-sections for the ⁷⁶Ge(n,) reactions were derived relative to the cross-section of ¹⁹⁷Au using the absolute emission probabilities of the observed -ray energies. The methods used in this work result in smaller systematic uncertainties than those obtained in previous experiments.     

Enhanced quadrupole collectivity at N = 40: the case of neutron-rich Fe isotopes

The transition rates for the 2(1)+ states in (62,64,66)Fe were studied using the recoil distance Doppler-shift technique applied to projectile Coulomb excitation reactions. The deduced E2 strengths illustrate the enhanced collectivity of the neutron-rich Fe isotopes up to N = 40. The results are interpreted using the generalized concept of valence proton symmetry which describes the evolution of nuclear structure around N = 40 as governed by the number of valence protons with respect to Z ≈ 30. The trend of collectivity suggested by the experimental data is described by state-of-the-art shell-model calculations with a new effective interaction developed for the fpgd valence space.     

Partial-wave analysis of elastic <Superscript>4</Superscript>He<Superscript>4</Superscript>He scattering in the energy range 40–50 MeV

A partial-wave analysis of elastic ⁴He⁴He scattering is performed in the energy range 40–50 MeV.     

Measurement of the cross sections for the production of the isotopes <Superscript>74</Superscript>As, <Superscript>68</Superscript>Ge, <Superscript>65</Superscript>Zn,and <Superscript>60</Superscript>Co from natural and enriched germanium irradiated with 100-MeV protons

The cross sections for the production of the radioactive isotopes ⁷⁴As, ⁶⁸Ge, ⁶⁵Zn, and ⁶⁰Co in metallic germanium irradiated with 100-MeV protons were measured, the experiments being performed both with germanium of natural isotopic composition and germanium enriched in the isotope ⁷⁶Ge. The targets were irradiated with a proton beam at the facility for the production of radionuclides at the accelerator of the Institute for Nuclear Research (INR, Moscow). The data obtained will further be used to calculate the background of radioactive isotopes formed by nuclear cascades of cosmic-ray muons in new-generation experiments devoted to searches for the neutrinoless double-beta decay of ⁷⁶Ge at underground laboratories.     

Cross sections of multiparticle photonuclear reactions with <Superscript>203, 205</Superscript>Tl isotopes

An experiment on the irradiation of the natural mixture of ^203,205Tl isotopes by the bremsstrahlung beam of pulsed racetrack microtron RTM-70 (Skobeltsyn Institute of Nuclear Physics, Moscow State University) at an electron energy of 67.7 MeV was performed. The yields and integral cross sections of multiparticle photonuclear reactions with ^203,205Tl isotopes were measured.     

Production of exotic neutron-deficient isotopes near N,Z=50 in multinucleon transfer reactions

The multinucleon transfer reaction in the collisions of ~(40) Ca+ ~(124) Sn at Ec.m. = 128.5 MeV is investigated using the improved quantum molecular dynamics model. The measured angular distributions and isotopic distributions of the products are reproduced reasonably well by the calculations. The multinucleon transfer reactions of ~(40) Ca +~(112) Sn, ~(58) Ni + ~(112) Sn, ~(106) Cd + ~(112) Sn, and ~(48) Ca + ~(112) Sn are also studied. This demonstrates that the combinations of neutron-deficient projectile and target are advantageous for the production of exotic neutron-deficient nuclei near N,Z =50. The charged particles' emission plays an important role at small impact parameters in the de-excitation processes of the system. The production cross sections of the exotic neutron-deficient nuclei in multinucleon transfer reactions are much larger than those measured in the fragmentation and fusion-evaporation reactions. Several new neutron-deficient nuclei can be produced in the ~(106) Cd + ~(112) Sn reaction. The corresponding production cross sections for the new neutron-deficient nuclei,~(101,112) Sb,~(103) Te,and ~106,107) I,are 2.0 nb,4.1 nb,6.5 nb,0.4 μb and 1.0 μb,respectively.