States in86Sr,84Sr and87Y populated in the (p,t) reaction

The (p,t) reactions on⁸⁸Sr,⁸⁴Sr and⁸⁹Y have been carried out at a bombarding energy of 49.5 MeV. Some low-lying excitations in⁸⁶Sr and⁸⁴Sr associated with configurations of 1g _9/2 and 2p _1/2 neutrons have been identified. Levels populated to 4 MeV of excitation in the strontium nuclei and to 2.5 MeV in⁸⁷Y have been studied in the present experiment. In the case of⁸⁷Y most of the levels populated are of a complex nature.     

A study of 80,82,84Sr by (α, 2nγ) reactions

The ^AKr(α, 2nγ)^A+2Sr reactions have been studied by in-beam γ-ray spectroscopy for A = 78, 80, and 82. States with spins up to 10⁺ in ^82,84Sr and 6⁺ in ⁸⁰Sr are identified. The Sr nuclei undergo a transition from spherical to deformed ground states as neutrons are removed from the N = 50 shell. The systematics of these nuclei are compared with calculations based upon the shell model and interacting boson model.     

High spin states of 83Sr

The reactions ⁸⁰Kr(α, n)⁸³Sr and ⁸²Kr(α, 3n)⁸³Sr were used to populate excited states of high spin in ⁸³Sr. The de-excitation of these states was studied by in-beam γ-ray spectroscopy. A number of new high-spin states have been observed. The results are discussed within the framework of the Coriolis-coupling model and the cluster-core coupling model.     

Atomistic computer simulation studies of La1−xSrxVO3

Static computer simulation techniques have been employed for structural investigation of the La_1−xSr_xVO₃ series. Potential parameters for V³⁺-O²⁻ and V⁴⁺-O²⁻ have been derived which reproduces the crystal structures of end members with sufficient accuracy. Variations of lattice parameters and bond distances with Sr concentration have been studied. The calculated lattice parameters decrease with increase in the Sr concentration. A structural phase transition from orthorhombic to cubic is observed at 50% Sr doping level.     

Level structure of78Rb

The excited states of⁷⁸Rb have been investigated by means of in-beam andβ-γ spectroscopy. The production of⁷⁸Rb and theβ radioactivity of⁷⁸Sr have been made through the⁵⁴Fe(²⁸Si,3pn) and⁵⁴Fe(²⁸Si,2p2n) reactions, respectively. Four rotational bands have been observed in the high-spin band structure. The signature splitting is large in the two bands, while the other two bands have small splitting. A detailed low-lying level scheme of⁷⁸Rb has been constructed for the first time via theβ decay of⁷⁸Sr in order to search for a linking transition between the high-spin band head and low lying states.     

Performance parameters and uncertainty of the method for assessment of Sr concentration in small powder samples using α-Al2O3:C beta detectors

Non-destructive detection of very low concentrations of ⁹⁰Sr (about 0.4 Bq g⁻¹) inside powdered samples with masses below 200 mg (such as tooth enamel prepared for EPR measurements) is not a trivial task. Most of the conventional measurement techniques require a special chemical treatment or an enrichment process. Thin-layer α-Al₂O₃:C passive luminescence beta detectors have been successfully used for measuring dose rates due to beta decay of ⁹⁰Sr inside small samples. In this paper, a new refinement is introduced for the assessment of ⁹⁰Sr concentration in dental tissue using thin-layer α-Al₂O₃:C passive luminescence beta detectors. The performance parameters of passive luminescence beta detection (such as detection and quantification limits) have been evaluated using statistical analysis of the experimental results. The sources of uncertainty have been analyzed and the total uncertainty calculated using Monte Carlo simulations. The results of TL passive beta detection for measurement of ⁹⁰Sr concentrations are shown to be in good agreement with those obtained using low-level beta counting.     

Particle coupling to the octupole state in 89Sr from 88Sr(p,p')88Sr analog resonances and 88Sr(d,p)89Sr

A study has been made of the six most pronounced isobaric analog resonances in the ⁸⁸Sr(p, p')⁸⁸Sr (3^?) excitation function at E_p = 7.65, 7.80, 7.92, 8.78, 9.75, and 9.90 MeV. They are believed to have a simple structure in the parent nucleus ⁸⁹Sr consisting of the lowlying positive-parity, single-neutron spectrum of ⁸⁹Sr weakly coupled to the collective 3^? state in ⁸⁸Sr. A high-resolution ⁸⁸Sr(d, p)⁸⁹Sr experiment was performed to locate small 2f and 3p admixed fragments in ⁸⁹Sr which would allow these analog resonances their entrance widths. In addition, on-resonance ⁸⁸Sr(p, p')⁸⁸Sr (3^?) angular distributions were measured in order to determine the partial waves involved in the exit channel. Results are compared to a particlephonon coupling model, and overall selectivity, strengths, and angular distributions of the (p, p') analog resonances are consistent with the above interpretation.     

Levels in 74Se, 78, 80Kr and 84Sr and systematics of quasi-γ bands

Quasi-band structures in ⁷⁴Se, ^{78, 80}Kr and ⁸⁴Sr have been investigated using (p, 2nγ) reactions. The members of the quasi-γ band have been observed up to 5⁺ in ⁷⁴Se, ^{78, 80}Kr and up to 3⁺ in⁸⁴Sr. The analyses of the energy systematics of the quasi-γ bands studied in this mass region as well as in other regions make clear the evolution of the quasi-γ band to the γ-band in well-deformed nuclei. In addition to these positive-parity bands, negative-parity levels were observed in ⁷⁴Se, ⁸⁰Kr and ⁸⁴Sr.     

Superconductivity recurrence and charge carrier compensation effect in La2−xSrxCu0.94M0.06O4 (M = Fe,Co and Ni) system

In this paper, the substitution effect of Sr for La in three non-superconducting system La_2−xSr_xCu_0.94M_0.06O₄ (M = Fe, Co and Ni) have been systematically studied. As the concentration of Sr increases to around 0.20, the superconductivity is recovered. The peak at 695 cm⁻¹ in the infrared spectra which is assigned to the stretching mode of oxygen atoms in plane induced by M³⁺ doping is suppressed by Sr increasing, demonstrating that the holes introduced by the Sr substitution have been injected into the CuO₂ plane and compensate the localized electrons. These results suggest that the superconductivity recurrence is caused by the carrier compensation. The main origin of superconductivity suppression by the magnetic ions Fe/Co/Ni is the carrier localization effect.     

Studies on85Sr,86Sr,and101Tc

Results are given on angular correlation for cascadeγ rays from⁸⁵Sr,⁸⁶Sr, and¹⁰¹Tc; the level spins and transition multipole orders have been determined.     

A study of the 84Kr(α, 2nγ)86Sr reaction

Decay properties of levels of ⁸⁶Sr populated by the 28 MeV ⁸⁴Kr(α, 2nγ) reaction have been studied by in-beam γ-ray spectroscopy. The observation of several new levels with $\text{J ≧ 6}$ allows a detailed comparison of the 2p-2n structures of ⁸⁶Sr with those of neighboring N = 48 nuclei. The results are discussed in terms of the weak-coupling model.     

Study on the Separation of Carrier-Free Yttrium-90 from Strontium-90

The separation of carrier-free ⁹⁰Y from ⁹⁰Sr by solvent extraction with di-(2-ethylhexyl) phosphoric acid (HDEHP) in dodecane has been investigated in this study. The extraction equilibrium time, the effect of temperature, concentration of extractant, and hydrochloric acid concentration on this extraction system were examined. Based on the studies, the chemical procedure for the separation of carrier-free ⁹⁰ Y from its parent ⁹⁰Sr have been established. The chemical yield of ⁹⁰Y is about 80%. Meanwhile, the ⁹⁰Sr impurity is less than 1×10^?6% and the trace of extractant presented in the final product can be removed by fumed with HNO₃. Consequently, the preparation of millicurie of ⁹⁰Y is quite satisfactory for the adsorption in microsphere resin for radiotherapy applications.     

The status of strontium in biological apatites: an XANES/EXAFS investigation

Osteoporosis represents a major public health problem through its association with fragility fractures. The public health burden of osteoporotic fractures will rise in future generations, due in part to an increase in life expectancy. Strontium‐based drugs have been shown to increase bone mass in postmenopausal osteoporosis patients and to reduce fracture risk but the molecular mechanisms of the action of these Sr‐based drugs are not totally elucidated. The local environment of Sr²⁺ cations in biological apatites present in pathological and physiological calcifications in patients without such Sr‐based drugs has been assessed. In this investigation, X‐ray absorption spectra have been collected for 17 pathological and physiological calcifications. These experimental data have been combined with a set of numerical simulations using the ab initioFEFF9 X‐ray spectroscopy program which takes into account possible distortion and Ca/Sr substitution in the environment of the Sr²⁺ cations. For selected samples, Fourier transforms of the EXAFS modulations have been performed. The complete set of experimental data collected on 17 samples indicates that there is no relationship between the nature of the calcification (physiological and pathological) and the adsorption mode of Sr²⁺ cations (simple adsorption or insertion). Such structural considerations have medical implications. Pathological and physiological calcifications correspond to two very different preparation procedures but are associated with the same localization of Sr²⁺versus apatite crystals. Based on this study, it seems that for supplementation of Sr at low concentration, Sr²⁺ cations will be localized into the apatite network.     

Gamma-ray spectroscopy of short-lived fission products using the recoil separator “Lohengrin”

γ-spectra and half-lives of⁹⁰Br,⁹⁵Rb,⁹⁶Rb,⁹⁶Sr,⁹⁶Y,¹³²Sb and¹³²Sn have been measured using the unslowed fission fragment separator “Lohengrin”. Preliminary decay schemes for⁹⁰Kr,⁹⁵Sr,⁹⁶Sr and⁹⁶Y are given.     

First absolute mass measurements of short-lived isotopes

Absolute mass measurements of short-lived isotopes have been performed at the on-line mass separator ISOLDE at CERN by determining the cyclotron frequencies of ions confined in a Penning trap. The cyclotron frequencies for^{77,78,85,86,88}Rb and⁸⁸Sr ions could be determined with a resolving power of 3×10⁵ and an accuracy of better than 10⁻⁶, which corresponds to 100 keV for massA=100. The shortest-lived isotope under investigation was⁷⁷Rb with a half-life of 3.7 min. The resonances obtained for the isobars⁸⁸Rb and⁸⁸Sr were clearly resolved.     

Investigation of pairing vibration states in 88Sr and 90Zr via the (d, 6Li) reaction and search for α-vibration states

With a 45 MeV deuteron beam the ⁹⁴Mo(d, ⁶Li)⁹⁰Zr and ⁹²Zr(d, ⁶Li)⁸⁸Sr reactions have been studied to search for α-vibration states in ⁹⁰Zr and in ⁸⁸Sr. No evidence is found for such a state in both nuclei with a strength > 5 % than that of the ground state. Strongly excited 0⁺ states in ⁸⁸Sr and ⁹⁰Zr are those also seen in two-nucleon stripping and pickup reactions.     

Saturation of deformation atN=60 in the Sr isotopes

From the halflife oft _1/2=3.91 (16) ns for the 2₁ ⁺ state in¹⁰⁰Sr a deformation parameter ofβ=0.40(1) has been derived. Within the given uncertainties, this value is equal to the recently determinedβ-parameters for⁹⁸Sr and⁹⁹Sr, indicating that in the Sr isotopes saturation of deformation is reached immediately at its onset well before neutron midshell. This behaviour is reflected by the “twin” character of⁹⁸Sr and¹⁰⁰Sr with identical features of their unperturbed ground-state rotational bands. These observations are discussed in terms of strong two-nucleon interactions.     

Alpha-particle D-state and configuration-mixing effects in the 89Y(d, α)87Sr reaction

Angular distributions of cross sections and vector and tensor analyzing powers have been measured for low-lying levels populated by ⁸⁹Y(d, α)⁸⁷Sr reaction at 9.0, 12.0, and 16.0 MeV. Full finite-range DWBA calculations that include the effects of an α-particle D-state component and (L, J) mixing have been performed. The ground-state transition indicates that the D-state parameter D₂ = −0.30 ± 0.1 fm². The angular distributions of the tensor analyzing powers are very sensitive to the magnitude and sign of the mixing amplitudes and can be used to determine the neutron-proton configurations transferred. The mixing amplitudes for the 0.388 MeV and 0.873 MeV states in ⁸⁷Sr are established from the analysis.     

Physical properties of double perovskite compounds ALaVMoO6 (A=Ca, Sr, Ba)—a possible half-metallic antiferromagnetic system

Double perovskite compounds ALaVMoO₆ (A=Ca, Sr, Ba) have been synthesized and their electrical and magnetic properties have been investigated. Magnetization measurements have indicated the possible antiferromagnetic transitions at 120 and 130 K for A=Ca and Sr samples, respectively. Electrical resistivity ρ for this system shows metallic temperature dependence from 300 to 20 K, though the sample with A=Ca shows weak semiconducting behavior in the low temperature region (<70 K). Considering the magnetic and electrical properties and assuming the V³⁺S=1 and Mo⁴⁺S=1 valence and spin states, the samples with A=Ca and Sr can be promising candidates for half-metallic antiferromagnets.     

Isobaric analogue resonances in proton elastic scattering from 84Sr

The cross section for the reaction ⁸⁴Sr(p, p₀)⁸⁴Sr has been measured for proton energies in the range E_p = 4.18?6.73 MeV. Resonance parameters were determined for 15 isobaric analogue resonances. Spectroscopic factors calculated for the analogues by means of the R-matrix theory and the Green function method are compared with Spectroscopic factors determined from the ⁸⁴Sr(d, p)⁸⁵Sr reaction. Angular distributions were measured at E_p = 7 and 12 MeV in order to obtain optical model parameters.