Low-energy S(E) factor of 9Be(p, α)6Li and 9Be(p,d)8Be

Excitation functions and angular distributions of the ⁹Be(p, α)⁶Li and ⁹Be(p, d)⁸Be reactions have been measured over the energy range E _p = 16 to 390 keV. The data are dominated by one broad resonance including interference effects with a direct process. The effects of electron screening have also been observed, which are however significantly larger than expected. The deduced reaction rates at T₉ ≤ 1 are in excellent agreement with values given in a compilation.     

(e, 3e) Differential cross section of He (21 S) and He (23 S)

The angular distribution of the five-fold differential cross section for the electron impact double ionization of He (2¹ S) and He (2³ S) has been studied. The kinematical conditions for maxima/minima in the angular distribution for the two cases have been compared. The two-step process for the double ionization is found to contribute very little in the triplet case.     

High-Resolution Infrared and Millimeter-Wave Study of the v(3) = 1 State of HSiF(3) and DSiF(3)

Millimeter-wave spectra of HSiF₃ and DSiF₃ in the v₃ = 1 excited state have been measured from 100 to 490 GHz. Infrared spectra have been recorded in the ν₃ regions, ν₀ 424.0301 and 420.9320 cm⁻¹ in HSiF₃ and DSiF₃, respectively, with a resolution of 2.4 × 10⁻³ cm⁻¹. Since in both species the parameters α^B₃ and α^C₃ have very similar values, no K structure could be resolved in the ^QP and ^QR clusters for low-to-medium K values. For high J the effect of the ground state D_JK term more and more dominates and spreads the J clusters into opposite directions such that medium-to-high K components, particularly those with K = 3p, are resolved. Rotational and infrared data have been fitted together using a model up to sextic centrifugal distortion constants. No perturbations were indicated. Hot bands (ν₃ + nν₆)–nν₆ with n = 1, 2, and 3 have been detected and analyzed.     

Total cross sections for some (α, n) and (α, p) reactions in medium-weight nuclei

Total cross sections have been measured for the ⁴⁵Sc(α, n), ⁴⁶Ti(α, n), ⁵⁰Cr(α, n), ⁵¹V(α, n), ⁵⁴Fe(α, n) and ⁵⁸Ni(α, p) reactions, and stellar reaction rates have been calculated from them. These have been compared to recent theoretical calculations which used compound nuclear theory. The calculated values are generally higher than the experimental values by factors ranging from 2 to 10.     

Infrared spectrum of stannous oxide (SnO)

A tunable diode laser has been used to measure the infrared spectrum of stannous oxide (SnO) in the gas phase between 830 and 868 cm^?1. Measurements of the v = 1-0, 2-1, 3-2, and 4-3 transitions have been made at temperatures ranging from 930 to 1150°C. Over 175 infrared transitions of the nine most abundant SnO isotopic species have been combined with microwave measurements reported by others in a single least-squares analysis of the data to yield a set of eight Dunham coefficients for the X¹Σ⁺ state of SnO. The data have also been fit by a nonlinear least-squares procedure to obtain B_e, ω_e, and the first five Dunham potential constants. The band center for the vibrational transition of ¹²⁰Sn¹⁶O is found at ν₀ (v = 1?0) = 814.70249 ± 0.00027 cm^?1.     

EPR studies of Cu<Superscript>2+</Superscript>-doped bis(saccharinato)bis(pyridine)zinc(II) single crystals

The electron paramagnetic resonance spectra of Cu²⁺ impurities in bis(saccharinato)bis(pyridine)zinc(II) single crystals have been studied at room temperature in three mutually perpendicular planes. The angular variation of the spectra indicates the substitution of the host Zn²⁺ with Cu²⁺. Two magnetically inequivalent sites for Cu²⁺ have been observed. The spectra were fitted to the rhombic spin Hamiltonian. The spin Hamiltonian parameters and the molecular orbital coefficients were evaluated for the two sites. The ground-state wave function of Cu²⁺ ion in the lattice has been constructed.     

Electromigration Studies of Carrier-Free 239Np(V) in Aqueos Solutions

Ion mobilities of carrier-free ²³⁹Np(V) have been measured in aqueous solutions, T = 298.1 (1) K. Ion mobilities of ²³⁹NpO₂ ⁺ and its dependencies on pH of acidic inert electrolytes have been measured. In alkaline solutions the stoichimetric hydrolysis constants of NpO₂(OH) as well as NpO₂(OH)₂ ^? have been obtained. Complex formations of ²³⁹Np(V) with oxalate, tartrate, sulphate, acetate and citrate ligands have been studied in neutral solutions.     

A study of the50Cr(d,n)51Mn and54Fe(d,n)55Co reactions

The⁵⁰Cr(d, n)⁵¹Mn and⁵⁴Fe(d, n)⁵⁵Co reactions have been studied at an incident deuteron energy of 5.5 MeV. Angular distributions of neutron groups to a number of low-lying levels in the residual nuclei have been recorded. Time-of-flight techniques have been used to record neutron spectra. A liquid scintillator with pulse-shape discrimination property has been used as neutron detector. DWBA calculations have been performed and relative spectroscopic strengths determined for transitions with variousl _p values. The ratios between spectroscopic strengths forl _p =3 andl _p =1 transitions were found to be considerably larger than corresponding ratios obtained from the (³He,d) reactions. Two-step stripping processes competing with the direct stripping process are suggested as explanation of the discrepancy between the (d, n) and the (³He,d) results.     

Planar channeling of helium ions along (100), (110) and (111) MgO

Planar channelling of 1, 1.5 and 2 MeV ⁴He⁺ ions along (100), (110) and (111) MgO have been studied experimentally using Rutherford backscattering. Values of the half angle $\text{ψ}{}^{\mathrm{P}}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, shoulder half angle $\text{ψ}{}^{\mathrm{s}}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ and surface minimum yield x^P_min have been determined for channelling with respect to the two sublattices. Agreements and discrepancies with existing theories are discussed.     

Gamma-photon induced modifications in Polyvinylchloride (PVC) film

Gamma photon induced modifications in Polyvinylchloride (PVC) polymer have been studied in the dose range of 10¹-10⁶Gy at room temperature. Polyvinylchloride films have been irradiated with different doses of gamma radiation from a ⁶⁰Co source. To monitor the chemical and structural changes caused by gamma radiation IR and UV-Vis spectroscopy of pristine and irradiated PVC have been performed and using the spectral data some changes in the properties have been investigated. The spectral studies have indicated that at a dose of 10⁶Gy scissioning of the C-a bonds takes place. This scissioning of the chain initiates decomposition at a lower temperature. Thermal stability of the polymer reduces due to irradiation but the decomposition patterns remain the same. The optical band-gap is found to decrease due to irradiation at doses bigher than 10³Gy.     

Investigation of 28Si levels with the (α, γ) and (p, γ) reactions

Particle energies have been measured for resonances in the ²⁷Al(p, γ)²⁸Si and ²⁴Mg(α, γ)²⁸Si reactions with an accuracy of 0.5 × 10^?4 and 1 × 10^?4, respectively. The E_p = 991.88 ± 0.04 keV²⁷Al(p, γ)²⁸Si resonance served as calibration point. From these data the Q-value of the reaction ²⁷Al(p, α)²⁴Mg has been determined as 1600.14 ± 0.21 keV. Excitation energies of ²⁸Si levels have been measured with the ²⁷Al(p, γ)²⁸Si reaction; the reaction energy is Q = 11584.5 ± 0.4 keV.Of 33 resonances observed in the ²⁴Mg(α, γ)²⁸Si reaction (E_α = 1.5–3.8 MeV), energies, strengths and γ-ray decay have been measured; five of these resonances had not been reported previously. The γ-ray angular distribution measurements at three resonances yield the resonance J^π values and the mixing ratios of the strongest transitions involved in the decay. The 10.38 MeV level has J^π = 3⁺, T = 1. The arguments on which T-assignments can be based are critically reviewed. These arguments are used to assign T = 1 character to ¹⁹ states of ²⁸Si.     

Level structure of 42K from the 41(n, γ) and 41K(d,p) reactions

The γ-ray spectrum emitted after thermal neutron capture in ⁴¹K has been measured with pair and Ge(Li) spectrometers at the ILL high-flux reactor. About 630 transitions have been assigned to the decay of 133 excited states in ⁴²K. The level energies have been determined with a precison of 20 ppm; the neutron binding energy was determined to be E_B = 7533.82(15) keV. On the basis of the many transitions to known states, several spin-parity assignments have been made. In addition, high-resolution proton spectra of the reaction ⁴¹K(d,p) have been taken at 20MeV deuteron energy with the München Q3D spectrometer. These data have been essential in establishing the newly-found levels and in differentiating between primary and secondary transitions in the (n, γ) work. A statistical analysis of the level density and relative strengths of primary transitions is given.     

Energy levels of80,82Br from (p,nγ) reactions

The levels of odd-odd^{80, 82}Br nuclei have been investigated via^{80, 82}Se(p, nγ)^{80, 82}Br reactions. Excitation functions and angular distributions were analysed with the Hauser-Feshbach compound nucleus theory. 27 and 29 levels have been identified. The transitions connecting the first 1⁺ and 2^?levels have been studied by the delayed coincidence method and their half-lives are 7.8±0.5 ns and 7.2±0.8 ns for⁸⁰Br and⁸²Br respectively. The experimental results are discussed in the framework of thej- j coupling.     

Synthesis and Characterization of 2,2-Biimidazole Complexes of Oxocations of Molybdenum (VI,V) and Uranium(VI)

Abstract

2,2′-Biimidazole complexes of MoO₂ ⁺², MoO₂ ⁺ and UO₂ ⁺² have been prepared and characterized by elemental analysis, conductance; and ¹H NMR, IR and electronic spectra. Two types of complexes have been identified. Those obtained from slightly acidic solutions have the formulae MoO₂ (H₂bim)Cl₂.2H₂O 1, UO₂(H₂bim) (Ac)₂ 2 and UO₂(H₂bim)Cl₂.2H₂O 3; whereas those from alkaline solutions have the formulae Mo₂O₄(Hbim)₂.2H₂O 4, and MO₂(Hbim)₂ (M = Mo(VI) 5, U(VI) 6). The infrared spectra of these complexes show characteristic biimidazole frequencies in the 3200–2500, 1550–1000 and 750 cm^?1 regions as well as metal oxygen double bonds in the 900 cm^?1 region. The stoichiometries of the acetate complex has been confirmed from ¹H NMR signal ratios of bimidazole to acetate protons at 7.3 and 2.3 ppm, respectively. The electronic spectrum of molybdenum(V) complex showed d-d transition band at ?13,500 cm^?1 in accord with that reported for copper (d⁹) imidazole complexes; as well as peaks due to charge transfer bands at 30,000–26,000 cm^?1 Peaks assignable to BIM → U(VI) were located at ?26,600 cm^?1. The most probable structures of these complexes have been suggested.     

The study of the (n, α) and (n, γ α) reactions on143Nd

Partial cross sections have been measured for the¹⁴³Nd(n _th,α)¹⁴⁰Ce reaction and also for the two-step process¹⁴³Nd(n _th,γα)¹⁴⁰Ce. The results of the present work confirm previous data, but due to lower background, better statistics and resolution improved precision has been obtained. The double-humped structure in the observed (n, γ α) spectrum can still be explained through the Porter-Thomas fluctuations of the reduced partialγ andα widths.     

The (p,d) reaction at 65 MeV

The (p, d) reaction on ¹²C, ¹⁴N, ¹⁶O, ⁴⁰Ca and ⁹⁰Zr has been studied with 65 MeV incident protons. DWBA calculations have been carried out to investigate the importance of finite range and non-locality effects. The experimental angular distributions for the strong transitions have been compared to DWBA calculations to study the effect of the deuteron optical potential. This comparison supports the use of the adiabatic deuteron potential which includes the effect of deuteron breakup.     

Screening effects on ~(12)C+~(12)C fusion reaction

One of the important reactions for nucleosynthesis in the carbon burning phase in high-mass stars is the ~(12)C+~(12)C fusion reaction. In this study, we investigate the influences of the nuclear potentials and screening effect on astrophysically interesting ~(12)C+~(12)C fusion reaction observables at sub-barrier energies by using the microscopic α-αdouble folding cluster(DFC) potential and the proximity potential. In order to model the screening effects on the experimental data, a more general exponential cosine screened Coulomb(MGECSC) potential including Debye and quantum plasma cases has been considered in the calculations for the ~(12)C+~(12)C fusion reaction. In the calculations of the reaction observables, the semi-classical Wentzel-Kramers-Brillouin(WKB) approach and coupled channel(CC)formalism have been used. Moreover, in order to investigate how the potentials between ~(12)C nuclei produce molecular cluster states of ~(24)Mg, the normalized resonant energy states of ~(24)Mg cluster bands have been calculated for the DFC potential. By analyzing the results produced from the fusion of ~(12)C+~(12)C, it is found that taking into account the screening effects in terms of MGECSC is important for explaining the ~(12)C+~(12)C fusion data, and the microscopic DFC potential is better than the proximity potential in explaining the experimental data, also considering that clustering is dominant for the structure of the ~(24)Mg nucleus.     

Sorption of selenium(IV) and selenium(VI) onto magnetite

In this work, we have studied the sorption of selenium (⁷⁹Se is one of the main radionuclides in a spent nuclear fuel repository) on magnetite (Fe₃O₄), a mineral present in the near-field of a nuclear waste repository that might represent an important retardation factor for the mobility of many radionuclides.The sorption of both Se(IV) and Se(VI) onto magnetite has been fitted by a non-competitive Langmuir isotherm with Γ_max = (3.13 ± 0.07) × 10⁻⁶ mol m⁻² and K_L = (1.19 ± 0.07) × 10⁶ dm³ mol⁻¹ for Se(IV) and Γ_max = (3.5 ± 0.2) × 10⁻⁶ mol m⁻² and K_L = (3.0 ± 0.1) × 10⁵ dm³ mol⁻¹ for Se(VI).The variation of the sorption of selenium with pH has been modeled using the Triple Layer Surface Complexation Model and the equilibrium constants between selenium and magnetite have been obtained using the FITEQL program. For the case of Se(IV), the best fitting has been obtained using two inner-sphere complexes, FeOHSeO₃²⁻ and FeHSeO₃, while for Se(VI), the best fitting has been obtained considering only an outer-sphere complex, FeOH₂⁺SeO₄²⁻.The surface complexation reactions derived in this work are in agreement with those stated by other authors for sorption of Se(IV) and Se(VI) on hydrous iron oxides.     

Analysis and optimization of optical bistability in one-dimensional nonlinear photonic crystal with (HL)(D)(LH) and (LH)(D)(HL) structures

Although one-dimensional nonlinear photonic crystal (1D-NPC) has been widely studied, there is no comprehensive analysis on decreasing the bistability threshold power.In this paper, conditions required to create bistability have been specified for two types of structures of alternative high and low refractive index layers and defect layers with Kerr nonlinearity effect, in the order of (HL)^p(D)^q(LH)^p and (LH)^p(D)^q(HL)^p, where L and H denote low and high refractive index layers, respectively, D stands for the defect layers, p is the number of LH or HL layers and q is the number of defect layers.One of the essentials for the bistability is appropriate shifts of frequency of the defect mode, so the effect of the order of layer's arrangement in (1D-NPC) structures have been studied. Different structures have been introduced and the best structure for the lowest bistability threshold power has been proposed. Nonlinear finite-difference time-domain (NFDTD) in C++ has been employed for simulation.     

Be9(d,p),(d,t),(d,a)反应研究

本文在E_d=0.1—2.5MeV能量范围内,研究了Be⁹(d,p₀)Be¹⁰(0),Be⁹(d,p₁)Be¹⁰(3.368MeV),Be⁹(d,t₀)Be⁸(0),Be⁹(d,α₀)Li⁷(0)及Be⁹(d,α₁)Li⁷(0.478MeV)诸反应。在E_d=0.150,0.220,0.401,0.706,1.005,1.301,1.484,1.750,2.000,2.250和2.500MeV共十一个能量上分别测量了这五群出射粒子在θ_L=10—155°区间的角分布。在θ_L=135°,E_d=0.1—2.5MeV,在θ_L=95°,E_d=0.1—2.2MeV,和在θ_L=112.5°,E_d=0.5—2.5MeV测量了Be⁹(d,p₀)Be¹⁰的激发函数。在θ_L=135°和112.5°,E_d=1.2MeV,用较厚靶(100—300μg/cm²)测量了Be⁹(d,p₀)Be¹⁰(0)反应的截面绝对值,结果为σ_(p0)(θ_L=135°)=1.60mb/sr,σ_(p0)(θ_L=112.5°)=1.55mb/sr。这样就得到了在此能区内,这五群出射粒子的截面情况。对所得结果进行了一些讨论。