Mi (i = 1-5) subshell fluorescence and Coster-Kronig yields for elements with 67 ? Z ? 92

A complete set of the M_i (i = 1-5) subshell fluorescence and Coster-Kronig (CK) yields has been generated by interpolation for elements with 67 ? Z ? 92 from the Dirac-Hartree-Slater (DHS) model based values tabulated for a limited number of elements, considering the cutoff/onset of different CK transitions in accordance with the CK transition energies evaluated in the present work. The CK transition energies have been deduced from tabulated values of the Dirac-Hartree-Fock-Slater model based neutral atom binding energies [K. Huang, M. Aoyagi, M.H. Chen, B. Crasemann, H. Mark, At. Data Nucl. Data Tables 18 (1976) 243] and the L_i (i = 1-3) subshell CK transition energies [M.H. Chen, B. Crasemann, K. Huang, M. Aoyagi, H. Mark, At. Data Nucl. Data Tables 19 (1977) 97] in order to establish the cutoff/onset of different CK transitions at specific atomic numbers. A second set of the M_i (i = 1-5) subshell fluorescence yields have also been deduced using radiative widths computed from the Dirac-Fock (DF) model based X-ray emission rates, and the total widths reevaluated to incorporate the DF model based radiative widths in place of those based on the DHS model. Further, the CK-corrected (ν_i) and average fluorescence (?_M) fields, which are experimentally important, have been evaluated from the generated set of CK yields and two sets of fluorescence yields.     

Li (i = 1-3) subshell X-ray production cross sections and fluorescence yields for some elements with 56 ? Z ? 68 at 22.6 keV

The L_k (k = l, α, β_1,4, β_3,6, β_2,15,9,10,7, γ_1,5 and γ_2,3,4) X-ray production (XRP) cross sections have been measured for six elements with 56 ? Z ? 68 at 22.6 keV incident photon energy using the EDXRF spectrometer. The incident photon intensity, detector efficiency and geometrical factors have been determined from the K X-ray yields emitted from elemental targets with 22 ? Z ? 42 in the same geometrical setup and from knowledge of the K XRP cross sections. The L₁ and L₂ subshell fluorescence yields have been deduced from the present measured L_k XRP cross sections using the relativistic Hartree-Fock-Slater (HFS) model based photoionization cross sections. The present deduced ω₁ (exp) values have been found to be, on an average, higher by 15% and 20% than those based on the Dirac-Hartree-Slater (DHS) model and the semi-empirical values compiled by Krause, respectively, for elements with 60 ? Z ? 68.     

Ga NMR and magnetic susceptibility in δ-phase of Pu1−xGax (x = 0.05, x = 0.08) alloys

⁶⁹Ga nuclear magnetic resonance spectra, line shifts (⁶⁹K) and nuclear spin-lattice relaxation rate have been measured in the 20 years aged Pu_0.95Ga_0.05 and in fresh prepared Pu_0.92Ga_0.08 alloys, stabilized δ-phase, at magnetic field of 9.4 T in the temperature range (10-500) K. The line shift and are determined correspondingly by the static and fluctuating-in-time parts of the local magnetic field that originates in transferred hyperfine coupling the Ga nuclear spin with the nearest f-electron environment of more magnetic Pu.Temperature behavior of the resonance properties is found the same in fresh Pu_0.92Ga_0.08 and aged Pu_0.95Ga_0.05 alloy. The NMR results are in favor that δ-phase of Pu_1−xGa_x alloys represents at T > 200 K the Kondo lattice, in which the localized electronic spins fluctuate independently from each other without any macroscopic coherence. The coherent state like in heavy-fermion liquids emerges in Pu_0.95Ga_0.05 below T^∗ = 200 K. A little bit higher estimate of crossover temperature T^∗ = 250 K was founded for Pu_0.92Ga_0.08.     

L1 and L2 sub-shell fluorescence yields for elements with 64 ? Z ? 70

The L₁ and L₂ sub-shell fluorescence yields have been deduced for elements with 64 ? Z ? 70 from the L_k(k = l, α, β_1,4, β_3,6, β_2,15,9,10,7, γ_1,5 and γ_2,3,4) X-ray production cross sections measured at 22.6 keV incident photon energy using a spectrometer involving a disc type radioisotope of Cd¹⁰⁹ as a photon source and a Peltier cooled X-ray detector. The incident photon intensity, detector efficiency and geometrical factor have been determined from the K X-ray yields emitted from elemental targets with 20 ? Z ? 42 in the same geometrical setup and from knowledge of the K shell cross sections. The present deduced ω₁(exp) values, for elements with 64 ? Z ? 70, are found to be in good agreement with those tabulated by Campbell (J.L. Campbell, Atom. Data Nucl. Data Tables 95 (2009) 115), where as these are, on an average, higher by 19% and 24% than those based on the Dirac-Hartree-Slater model (S. Puri et al., X-ray Spectrometry 22 (1993) 358) and the semi-empirical values compiled by Krause (M.O. Krause, J. Phys. Chem. Ref. Data 8 (1979) 307), respectively. The present deduced ω₂(exp) values are found to be in good agreement with those based on the Dirac-Hartree-Slater model and are higher by up to ∼13% than the semi-empirical values for the elements under investigation.     

Nuclear half-lives for α-radioactivity of elements with 100 ? Z ? 130

Theoretical estimates for the half-lives of about 1700 isotopes of heavy elements with 100 ? Z ? 130 are tabulated using theoretical Q-values. The quantum mechanical tunneling probabilities are calculated within a WKB framework using microscopic nuclear potentials. The microscopic nucleus-nucleus potentials are obtained by folding the densities of interacting nuclei with a density-dependent M3Y effective nucleon-nucleon interaction. The α-decay half-lives calculated in this formalism using the experimental Q-values were found to be in good agreement over a wide range of experimental data spanning about 20 orders of magnitude. The theoretical Q-values used for the present calculations are extracted from three different mass estimates viz. Myers-Swiatecki, Muntian-Hofmann-Patyk-Sobiczewski, and Koura-Tachibana-Uno-Yamada.     

Measurement of L X-ray fluorescence cross-sections for elements with 45 ? Z ? 50 using synchrotron radiation at 8 keV

The L shell fluorescence cross-sections of the elements in range 45 ? Z ? 50 have been determined at 8 keV using Synchrotron radiation. The individual L X-ray photons, Ll, Lα, Lβ_I, Lβ_II, Lγ_I and Lγ_II produced in the target were measured with high resolution Si(Li) detector. The experimental set-up provided a low background by using linearly polarized monoenergetic photon beam, improving the signal-to-noise ratio. The experimental cross-sections obtained in this work were compared with available experimental data from Scofield [1] and [2] Krause [3] and [4] and Scofield and Puri et al. [5] and [6].These experimental values closely agree with the theoretical values calculated using Scofield and Krause data, except for the case of Lγ, where values measured of this work are slighter higher.     

Stopping power measurements of heavy ions (3 ? Z1 ? 14) in Mylar foil by time-of-flight spectrometry

Heavy ions elastic recoil detection analysis coupled with time of flight spectrometer (HIERDA_ToF-E) have been used to measure energy loss of charged particles in thin absorber. The stopping power of heavy ions has been determined in Mylar for ²⁸Si, ²⁷Al, ²⁴Mg, ¹⁹F, ¹⁶O, ¹²C and ⁷Li ions over a continuous range of energies 0.14-0.80 MeV/nucleon. The ions were recoils from the bombardment of different samples (Si, MgO, Al₂O₃, LiF and C) with a 27.5 MeV Kr⁺ beam. The energy loss of the recoil atoms is measured with and without additional foils placed in front of a Surface Barrier Detector (SBD). The energy of individual ions is determined from its ToF data; the exit energy after the stopping foil is measured using the SBD detector. We have compared our stopping values to those predicted by SRIM-2008 computer code, ICRU-73 stopping data tables, MSTAR calculations and to the published data from literature. The results show good agreement with limited existing data but indicate a large deviation among the predicted theoretical values at the low energy side of the stopping maximum peak.     

Measurements of activation cross sections for Lu(n, α)Tm,Lu(n, α)Tm and Lu(n, p)Yb reactions induced by neutrons around 14 MeV

The cross sections for the ¹⁷⁵Lu(n, α)¹⁷²Tm, ¹⁷⁶Lu(n, α)¹⁷³Tm and ¹⁷⁵Lu(n, p)^175m+gYb reactions have been measured in the neutron energy range of 13.5–14.8 MeV using the activation technique. The first data for ¹⁷⁵Lu(n, α)¹⁷²Tm reaction cross sections are presented. In our experiment, the fast neutrons were produced via the ³H(d, n)⁴He reaction on K-400 Neutron Generator at Chinese Academy of Engineering Physics (CAEP). Induced gamma activities were measured by a high-resolution (1.69 keV at 1332 keV for ⁶⁰Co) gamma-ray spectrometer with high-purity germanium (HPGe) detector. Measurements were corrected for gamma-ray attenuations, random coincidence (pile-up), dead time and fluctuation of neutron flux. The neutron fluences were determined by the cross section of ⁹³Nb(n, 2n)^92mNb or ²⁷Al(n, α)²⁴Na reactions. The neutron energy in the measurement was by the cross section ratios of ⁹⁰Zr(n, 2n)^89m+gZr and ⁹³Nb(n, 2n)^92mNb reactions. The results were discussed and compared with experimental data found in the literature and with results of published empirical formulae.     

An analytical multigroup benchmark for (n, γ) and (n, n′, γ) verification of diffusion theory algorithms

The angular flux for the “rod model” describing coupled neutron/gamma (n, γ) diffusion has a particularly straightforward analytical representation when viewed from the perspective of a one-group homogeneous medium. Cast in the form of matrix functions of a diagonalizable matrix, the solution to the multigroup equations in heterogeneous media is greatly simplified. We shall show exactly how the one-group homogeneous medium solution leads to the multigroup solution.     

Systematics studies of (n, α) reaction cross sections at 14.5 MeV neutrons energy

A new semi-empirical formula for the calculation of the (n, α) cross-section at 14.5 MeV neutron energy is obtained. It is based on the pre-equilibrium exciton and evaporation models and uses the Droplet model of Myers and Swiatecki to express the reaction energy Q(n, α). The systematics behavior of the different terms of the Droplet model involved in Q(n, α) was checked individually before choosing the pertinent terms and setting up the formula. Fitting this formula to the existing cross-section data, the adjustable parameters have been determined and the systematics of the (n, α) reaction have been studied. The predictions of this formula are compared with those of the existing formulae and with the experimental data. The formula with five parameters is found to give a better fit to the data than the previous comparable formulae.     

Energy loss straggling in thick mylar polymeric foils for swift heavy ions in fractional energy loss limits ΔE/E ∼ 5-80%

The energy loss straggling in thick mylar (monomer composition: C₁₀H₈O₄) polymeric foils has been measured for swift heavy ions covering Z = 3-22, in the fractional energy loss limits ΔE/E ∼ 5-80%. These measured straggling values have been compared with the most commonly used Bethe-Livingston collisional straggling formulation after modifying it suitably for thick targets. Further, the charge-exchange straggling values have been extracted from the measured values and were found to be consistently higher than the corresponding values deduced from Yang’s et al. formulation. Finally, an analytical expression has been developed for charge-exchange straggling for ion-polymer combinations, considered in the present study.     

Excitation functions of (n, α) reaction cross-sections for some important isotopes from threshold to 20 MeV

The (n, α) reaction cross-sections from threshold to ∼20 MeV on some important nuclides ⁴²Ca, ^50,53Cr, ^56,57Fe, ^58,62Ni, and ^63,65Cu involved in the reactor shielding design have been calculated using the Hauser–Feshbach statistical model with preequilibrium effects by involving PCROSS option in Empire 2.19. The transmission coefficients for neutrons in the entrance channel are calculated using the optical model potential of Koning. In the exit channel optical model potential of Avrigeanu has been used. The experimental values have been chosen carefully for all the isotopes, from EXFOR data base. The calculations are compared with existing experimental data as well as with evaluated data files (ENDF/B-VI.0 and JENDL-3.3). A good agreement between the calculated and experimental data validates the nuclear model approaches with increased predictive power to supplement and extend the nuclear database that is required for several applications.     

Measurement of neutron capture cross-section of the Ga(n, γ)Ga reaction at 0.0536 eV energy

The neutron capture cross-section for the ⁷¹Ga(n,  γ)⁷²Ga reaction at 0.0536 eV energy was measured using activation technique based on TRIGA Mark-II research reactor. The ¹⁹⁷Au(n, γ)¹⁹⁸Au monitor reaction was used to determine the effective neutron flux. Neutron absorption and γ-ray attenuation in gallium oxide pellet were corrected in determination of cross-section. The cross-section for the above reaction at 0.0536 eV amounts to 2.75 ± 0.14 b. As far as we know there are no experimental data available at our investigated energy. So far we are the first, who carried out experiment with 0.0536 eV neutrons for cross-section measurement. The present result is larger than that of JENDL-3.3, but consistent within the uncertainty range. The value of ENDF/B-VII is higher than this work. The result of this work will be useful to observe energy dependence of neutron capture cross-sections.     

Thermal neutron cross-section and resonance integral of the W(n, γ)W reaction

We measured the thermal neutron cross-section and the resonance integral of the reaction ¹⁸⁶W(n, γ)¹⁸⁷W by the activation method using a ¹⁹⁷Au(n, γ)¹⁹⁸Au monitor reaction as single comparator. The high-purity natural W and Au metallic foils with and without a cadmium shield case of 0.5 mm thickness were irradiated in a neutron field of the Pohang neutron facility. The induced activities in the samples were measured by high-resolution γ-ray spectrometry with a calibrated p-type high-purity Ge detector. The necessary correction factors for γ-ray attenuation (F_g), thermal neutron self-shielding (G_th), and resonance neutron self-shielding (G_epi) effects, and the epithermal neutron spectrum shape factor (α) were taken into account. The thermal neutron cross-section for the ¹⁸⁶W(n, γ)¹⁸⁷W reaction has been determined to be 37.2 ± 2.1 barn, relative to the reference value of 98.65 ± 0.09 barn for the ¹⁹⁷Au(n, γ)¹⁹⁸Au reaction. The present result is, in general, in good agreement with most of the experimental data and the recently evaluated value of ENDF/B-VII.0 by 5.7%. By assuming the cadmium cut-off energy of 0.55 eV, the resonance integral obtained is 461 ± 39 barn, which is determined relative to the reference values of 1550 ± 28 barn for the ¹⁹⁷Au(n, γ)¹⁹⁸Au reaction. The present resonance integral value is in general good agreement with the recently measured values by 9%. The present result is lower than the evaluated ones by 10-13%.     

Hydrogen-induced disproportionation characteristics of Zr(1 − x)Hf(x)Co(x = 0, 0.1, 0.2 and 0.3) alloys

Doping hafnium to partially substitute zirconium in ZrCo is a promising strategy to improve the ability to resist hydrogen-induced disproportionation. Herein, Zr(1 ? x)Hf(x)Co(x = 0,0.1,0.2, and 0.3) alloys were fabricated by arc melting and the effect of hafnium substitution ratio and temperature on their hydrogen-induced disproportionation was studied. Additionally, the disproportionated products were characterized by XRD, DSC and TDS. Results showed that disproportionation rate and the extent of disproportionation decreased with hafnium substitution ratio increasing from 0 to 30% and increased with temperature increasing from 400 °C to 550 °C. It was exciting that Zr0.7Hf0.3Co alloy had much better ability of anti-disproportionation than ZrCo in hydrogen pressure of about 200 kPa when temperature increasing from 400 °C to 550 °C, which was practical for tritium application.     

Proton elastic scattering and proton induced γ-ray emission cross-sections on Na from 2 to 5 MeV

Differential cross-sections for proton elastic scattering on sodium and for γ-ray emission from the reactions ²³Na(p,p′γ)²³Na (E_γ = 440 keV and E_γ = 1636 keV) and ²³Na(p,α′γ)²⁰Ne (E_γ = 1634 keV) were measured for proton energies from 2.2 to 5.2 MeV using a 63 μg/cm² NaBr target evaporated on a self-supporting thin C film.The γ-rays were detected by a 38% relative efficiency Ge detector placed at an angle of 135° with respect to the beam direction, while the backscattered protons were collected by a Si surface barrier detector placed at a scattering angle of 150°. Absolute differential cross-sections were obtained with an overall uncertainty estimated to be better than ±6.0% for elastic scattering and ±12% for γ-ray emission, at all the beam energies.To provide a convincing test of the overall validity of the measured elastic scattering cross-section, thick target benchmark experiments at several proton energies are presented.     

Measurement of cross sections for (n, 2n), (n, p) and (n, α) reactions on germanium isotopes induced by 14 MeV neutrons

Activation cross sections at the neutron energy about 14 MeV on germanium isotopes have been measured, employing the activation technique and γ-ray spectrometry. The data of the cross section are reported for the (n, 2n), (n, p) and (n, α) reactions. The neutron flux was determined using the monitor reactions ²⁷Al (n, α) ²⁴Na and the neutron energies were measured by the method of cross section ratios for ⁹⁰Zr (n, 2n) ⁸⁹Zr to ⁹³Nb (n, 2n) ^92mNb reactions. The measured results were compared with the other measurements.     

Depth profiling of Mg by 2010 keV resonance of Mg(p,p′γ)Mg nuclear reaction

Studies on the characteristics of 2010 keV resonance in ²⁴Mg(p,p′γ)²⁴Mg nuclear reaction for depth profiling Mg in thin films are reported. The resonance reaction, based on the detection of characteristic 1368 keV γ-rays, enables interference free measurement of Mg down to 2 × 10²⁰ atoms/cm³ and has a probing depth of about 20 μm. The width of the resonance extracted from excitation curves for thick (>180 nm) thermally grown elemental Mg films, by SPACES is about 350 ± 50 eV. The reaction has been used to depth profile Mg in a Mg/Ti/Mg/Si film which provides interesting information on interfacial mixing involving Ti layer and the underlying Mg layer.     

~3He(d,p)~4He反应截面的测量

本工作对~3He(d,p)~4He反应在实验室系90°角进行了激发函数的测量。入射氘的能量为200千电子伏到1000千电子伏。在激发函数的共振峰上(E_d=420千电子伏),测量了微分截面绝对值。利用此反应在低入射能量情况下角分布为各向同性的特点,推得了全截面为847±53毫靶。将此实验结果和前人的工作结果进行了比较。     

穆斯堡尔谱研究Fe_2(C_2O_4)_3/HY和Fe_2(C_2O_4)_3/HZSM-5在氢气中的热分解

以穆斯堡尔谱研究了Fe_2(C_2O_4)/HY和Fe(C_2O_4)_3/HZSM-5在氢气中的热分解。草酸铁(Ⅲ)在HY和HZSM-5沸石上不同的热分解方式主要是由于两种沸石的表面酸性不同。HY沸石的硅铝比较低,表面酸性较弱,草酸铁(Ⅲ)在其表面发生离解吸附,结果一部分Fe(Ⅲ)直接同表面羟基配位,这部分Fe(Ⅲ)具有较大的四极分裂值,且难以被还原;另一部分Fe(Ⅲ)受HY沸石表面作用较弱,其四极分裂值较小,240℃时被还原