Low-energy measurement of the 7Be(p,gamma)8B cross section

We have measured the cross section of the 7Be(p,gamma)8B reaction for E(c.m.) = 185.8, 134.7, and 111.7 keV using a radioactive 7Be target (132 mCi). Single and coincidence spectra of beta+ and alpha particles from 8B and 8Be* decay, respectively, were measured using a large acceptance spectrometer. The zero energy S factor inferred from these data is 18.5+/-2.4 eV b and a weighted mean value of 18.8+/-1.7 eV b (theoretical uncertainty included) is deduced when combining this value with our previous results at higher energies.     

Inference in lognormal multidimensional diffusion processes with exogenous factors: Application to modelling in economics

The multidimensional lognormal diffusion process with exogenous factors is treated using the Kolmogorov equations, and the mean vector and covariance matrix are estimated using discrete sampling by the maximum-likelihood method. Also, this process is constructed as a solution of a multidimensional stochastic differential equation, and an estimation is made through the maximum-likelihood method to infer the parameters of the exogenous factors, this time using continuous sampling. Finally, a test for a hypothesis based on these parameters is constructed.     

Structural properties of reciprocal form factor in neutral atoms and singly charged ions

Structural characteristics of the spherically averaged internally folded density or reciprocal form factor Br are studied within the Hartree-Fock framework for 103 neutral atoms, 54 singly charged cations, and 43 anions in their ground state. The function Br is classified throughout the Periodic Table into three types: (i) monotonic decrease from the origin, (ii) maximum at r=0 and a negative minimum at r>0, and (iii) a local maximum at r=0 and a pair maximum-minimum out of the origin. A detailed study of the corresponding properties for individual subshells as well as their relative weight for the total Br is also carried out. For completeness, the analytical Br for hydrogenlike atoms in both ground and excited states is also analyzed.     

Reactions induced by 35 MeV 6He beam on 12C and 14C

The ⁶He+^12,14C scattering and reactions have been studied using a 35 MeV ⁶He radioactive beam and preliminary results are presented. The three-body reaction ⁶He+¹²C ↦ ¹⁰Be+2 α has been clearly identified and sequential decay of intermediate states in ¹⁴C has been studied. Search for an analog reaction on ¹⁴C, ⁶He+¹⁴C ↦ ¹²Be+2 α, has not given conclusive results yet. Other interesting reactions with this entrance channel are discussed.     

The S(E) factor of7Li(p, γ)8Be and consequences for S(E) extrapolation in7Be(p, γ0)8B

Excitation functions and forward-backward anisotropies have been measured for the⁷Li(p, )⁸Be capture reaction over the proton energy rangeE _p =100 to 1500 keV, using a 4 summing crystal and Ge(Li) detectors, respectively. The data show at all energies the presence of El and M1 capture amplitudes arising from the direct capture (DC) process and theE _R =441 and 1030 keV resonances, respectively. Due to the observed DC process, the present data increase significantly the reaction rates (up to a factor of 110) compared to values given in the compilation. The data and their analyses remove the recent criticism on DC model calculations, which had implied a significant reduction in the extrapolated S(E) factor for⁷Be(p,)B and thus in the predicted flux of high-energy solar neutrinos; thus, the solar neutrino problem is still with us.Supported in part by the Deutsche Forschungsgemeinschaft (Ro429/21-3 and Ro429/21-4) and the German-Hungarian Collaboration (X238.6 and OTKA3808)     

New bounds for the atomic charge and momentum densities at the origin

The “Stieltjes moment problem” technique together with the positivity and monotonic decreasing properties of the electronic density of an atom is used to find new and more accurate lower bounds for the charge density at the nucleus and the momentum density at the origin, in terms of radial and momentum expectation values, respectively. Bounds depending on two and three expectation values are given explicitly and a Hartree-Fock study of their quality is carried out. Also, the behavior of the new bounds at largeZ's is discussed. The Stieltjes technique allows to find lower bounds of better accuracy by including expectation values of higher order.     

Study of some interelectronic properties in helium-like atoms

By means of the optimumM-term Hylleraastype wavefunctions with 1≦M≦6 we study various interelectronic properties of the Helium-like atoms with nuclear chargeZ=1, 2, 3, 5 and 10. Leth(u) denote the spherically averaged electron-pair density of a finite many-electron system. Firstly we found that the intracule functionh(u)/u ^α of the above-mentioned atoms is (i) monotonically decreasing from the origin for α≥α₁ and (ii) convex for α≥α₂, where α₁ and α₂ are positive constants which depend onZ andM. Then we show that the electron-electron cusp condition, i.e. thath′(0)=h(0), may be extended in the sense that the inequalityh(u)?h′(u)≧0 is valid for anyu≥0. Thirdly, it is shown that the inequalities involving three interelectronic moments 〈u ⁿ 〉 recently found by the authors are, at times, of great quality. Finally the goodness of some bounds to the characteristics of the maximum ofh(u) and to the total interelectronic repulsion energy is discussed in detail.     

Calculation of the formation constant of the 1:1 complex between manganese(II) and the anion of 2-mercaptopyridine N-oxide (pyrithione) by polarographic measurements

Polarograms of mixtures of Mn^II and the anion of 2-mercaptopyridine N-oxide (pyrithione) in neutral media do not show separate waves for the metal ion, either complexed or not, nor for the ligand, free or in the complex. The two-electron reduction of Mn^II is shown to be an E_rE_i process in the absence of ligand and C_rE_rE_i process in the presence of ligand, with a fast previous reaction. From measurements made at constant Mn^II concentration and variable ligand concentration it is shown that the 1:1 complex is formed. The logarithm of the formation constant of this complex is obtained from these and other measurements, this value being log K_f = 3.76 ± 0.03.