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317 results on '"Leiste, H."'

3. Cross sections for proton-induced reactions on Pd isotopes at energies relevant for the gamma process

Author

Dillmann, I., Coquard, L., Domingo-Pardo, C., Käppeler, F., Marganiec, J., Uberseder, E., Giesen, U., Heiske, A., Feinberg, G., Hentschel, D., Hilpp, S., Leiste, H., Rauscher, T., and Thielemann, F. -K.

Subjects
Astrophysics - Solar and Stellar Astrophysics, Nuclear Experiment
Abstract

Proton-activation reactions on natural and enriched palladium samples were investigated via the activation technique in the energy range of E_p=2.75 MeV to 9 MeV, close to the upper end of the respective Gamow window of the gamma process. We have determined cross sections for 102Pd(p,gamma)103Ag, 104Pd(p,gamma)105Ag, and 105Pd(p,n)105Ag, as well as partial cross sections of 104Pd(p,n)104Ag^g, 105Pd(p,gamma)106Ag^m, 106Pd(p,n)106Ag^m, and 110Pd(p,n)110Ag^m with uncertainties between 3% and 15% for constraining theoretical Hauser-Feshbach rates and for direct use in gamma-process calculations., Comment: 12 pages, accepted for publication in Phys. Rev. C (2011)

Published
2011
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4. Constraining the S factor of 15N(p,g)16O at Astrophysical Energies

Author

LeBlanc, P. J., Imbriani, G., Goerres, J., Junker, M., Azuma, R., Beard, M., Bemmerer, D., Best, A., Broggini, C., Caciolli, A., Corvisiero, P., Costantini, H., Couder, M., deBoer, R., Elekes, Z., Falahat, S., Formicola, A., Fulop, Zs., Gervino, G., Guglielmetti, A., Gustavino, C., Gyurky, Gy., Kaeppeler, F., Kontos, A., Kuntz, R., Leiste, H., Lemut, A., Li, Q., Limata, B., Marta, M., Mazzocchi, C., Menegazzo, R., O'Brien, S., Palumbo, A., Prati, P., Roca, V., Rolfs, C., Alvarez, C. Rossi, Somorjai, E., Stech, E., Straniero, O., Strieder, F., Tan, W., Terrasi, F., Trautvetter, H. P., Uberseder, E., and Wiescher, M.

Subjects
Nuclear Experiment
Abstract

The 15N(p,g)16O reaction represents a break out reaction linking the first and second cycle of the CNO cycles redistributing the carbon and nitrogen abundances into the oxygen range. The reaction is dominated by two broad resonances at Ep = 338 keV and 1028 keV and a Direct Capture contribution to the ground state of 16O. Interference effects between these contributions in both the low energy region (Ep < 338 keV) and in between the two resonances (338

Published
2010
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33. Ignition in ternary Ru/Al-based reactive multilayers—Effects of chemistry and stacking sequence.

Author

Pauly, C., Woll, K., Gallino, I., Stüber, M., Leiste, H., Busch, R., and Mücklich, F.

Subjects
IGNITION temperature, THERMAL properties of condensed matter, MULTILAYERS, INTERFACES (Physical sciences), HAFNIUM
Abstract

While self-propagating reactions in metallic multilayers have been known since the early 1990s, the vast majority of research has been conducted on binary systems comprising either elemental or alloyed layers. The properties of reaction and ignition in these samples are, for a given composition, mainly determined by the bilayer thickness as main design parameter. Here, we present how the stacking sequence is established as an additional design parameter when going from binary to ternary layered systems. The basis for this study is reactive Ru/Al multilayers which are extended to ternary samples by introducing a third element (Ni, Pt, or Hf) as a third, individual component. It is shown that exothermic solid state reactions at the layer interfaces and grain boundaries control the ignition temperature. Furthermore, the stacking sequence determines the specific volume density of phase boundaries and, thus, the magnitude of contribution of these reactions to the process of ignition. While the addition of hafnium is found to have little to no effect on ignition, nickel and platinum lower the ignition temperatures by up to 150 °C (Ni) and 230 °C (Pt), respectively. This can be attributed to the exothermic formation of Ni2Al9, amorphous a-(Al,Pt), and Pt2Al3 which are formed at temperatures significantly lower than that of RuAl6 which is the driving reaction for ignition in binary Ru/Al multilayers. [ABSTRACT FROM AUTHOR]

Published
2018
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39. HRXRD study of the effect of a nanoporous silicon layer on the epitaxial growth quality of GaN layer on the templates of SiC/por-Si/c-Si

Author

Seredin, P. V., Leiste, H., Lenshin, A. S., Mizerov, A. M., Seredin, P. V., Leiste, H., Lenshin, A. S., and Mizerov, A. M.

Abstract

Using High Resolution X-ray Diffraction (HRXRD) diagnostic techniques the influence of the transition layer of nanoporous silicon on the practical implementation and certain features of the epitaxial growth of GaN layers with the use of molecular beam epitaxy were investigated by means of plasma activation of nitrogen (MBE PA) on the templates of SiC/por-Si/c-Si. For the first time it was shown that introducing of the transition layer of nanoporous silicon in the template of SiC/por-Si/c-Si where the layer of 3C-SiC was obtained by substitution of the atoms had a number of indisputable advantages as compared with conventional silicon substrates. Particularly, such an approach, in fact, enabled a 90% reduction in the level of stresses in the crystalline lattice of the epitaxial GaN layer which was synthesized on SiC surface of SiC/por-Si/c-Si template by means of MBE PA technique as well as to decrease some of vertical dislocations within GaN layer. © 2020 The Authors

Published
2020

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