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15 results on '"F., Schu"'

1. Molecular dynamics in zeolitic host systems

Author

G. Ihlein, A. Huwe, Peter Behrens, J. Ka¨rger, F. Schu¨th, Ö. Weiß, Wilhelm Schwieger, and Friedrich Kremer

Subjects
Coordination number, Relaxation (NMR), Condensed Matter Physics, Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials, chemistry.chemical_compound, Molecular dynamics, chemistry, Chemical physics, Materials Chemistry, Organic chemistry, Molecule, Physical and Theoretical Chemistry, Zeolite, Ethylene glycol, Spectroscopy, Topology (chemistry), Broadband dielectric spectroscopy
Abstract

Broadband dielectric spectroscopy (10 −2 Hz - 10 9 Hz) is employed to study the molecular dynamics of the simple glassforming liquid ethylene glycol (EG) being confined to zeolites of varying size and topology. A sharp transition is observed from a single molecule dynamics (with an Arrhenius-type temperature dependence) to that of a liquid (with a temperature dependence of the mean relaxation rate according to a Vogel-Fulcher-Tammann-law (VFT-law)): While EG in silicalite and H-ZSM-5 (showing a single-molecule relaxation) has a coordination number of four, EG in zeolite beta or AIPO 4 -5 has a coordination number of five and behaves like a bulk liquid.

Published
2000
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2. The 14N(p,γ)15O measurement at low energy

Author

F. CONFORTOLA, D. BEMMERER, R. BONETTI, C. BROGGINI, P. CORVISIERO, H. COSTANTINI, J. CRUZ, A. FORMICOLA, Z. FU, LOP, G. GERVINO, A. GUGLIELMETTI, C. GUSTAVINO, G. GYU, RKY, G, IMBRIANI, A. P. JESUS, M. JUNKER, A. LEMUT, R. MENEGAZZO, P. PRATI, V. ROCA, C. ROLFS, M. ROMANO, G. ROSSI ALVAREZ, F. SCHU, MANN, E. SOMORJAI, O. STRANIERO, F. STRIEDER, H. P. TRAUTVETTER, S. ZAVATARELLI, TERRASI, Filippo, F., Confortola, D., Bemmerer, R., Bonetti, C., Broggini, P., Corvisiero, H., Costantini, J., Cruz, A., Formicola, Z., Fu, Lop, G., Gervino, A., Guglielmetti, C., Gustavino, G., Gyu, Rky, G, Imbriani, A. P., Jesu, M., Junker, A., Lemut, R., Menegazzo, P., Prati, V., Roca, C., Rolf, M., Romano, G., ROSSI ALVAREZ, F., Schu, Mann, E., Somorjai, O., Straniero, F., Strieder, Terrasi, Filippo, H. P., Trautvetter, and S., Zavatarelli

Published
2004

15. CNO hydrogen burning studied deep underground

Author

C. Rolfs, Daniel Bemmerer, Gy. Gyürky, Carlo Broggini, C. Rossi Alvarez, R. Menegazzo, R. Bonetti, F. Schümann, H. P. Trautvetter, G. Gervino, B. Limata, Gianluca Imbriani, Oscar Straniero, Frank Strieder, Filippo Terrasi, João Cruz, A. P. Jesus, F. Confortola, M. Junker, A. Guglielmetti, Mario R. Romano, A. Formicola, Zs. Fülöp, A. Lemut, H. Costantini, Detlef Rogalla, C. Gustavino, Vincenzo Roca, Paolo Prati, E. Somorjai, P. Corvisiero, Bemmerer, D., Confortola, F., Lemut, A., Bonetti, R., Broggini, C., Corvisiero, P., Costantini, H., Cruz, J., Formicola, A., Fulop, Z. s., Gervino, G., Guglielmetti, A., Gustavino, C., Gyurky, G. y., Imbriani, Gianluca, Jesus, A. P., Junker, M., Limata, B., Menegazzo, R., Prati, P., Roca, Vincenzo, Rogalla, D., Rolfs, C., Romano, Mario, Rossi Alvarez, C., Schuemann, F., Somorjai, E., Straniero, O., Strieder, F., Terrasi, F., Trautvetter, H. P., D., Bemmerer, A., Lemut, R., Bonetti, C., Broggini, P., Corvisiero, H., Costantini, J., Cruz, A., Formicola, Z., Fulop, G., Gervino, A., Guglielmetti, C., Gustavino, G., Gyurky, G., Imbriani, A. P., Jesu, M., Junker, B., Limata, R., Menegazzo, P., Prati, V., Roca, D., Rogalla, C., Rolf, M., Romano, C., ROSSI ALVAREZ, F., Schu, Mann, E., Somorjai, O., Straniero, F., Strieder, Terrasi, Filippo, and H. P., Trautvetter

Subjects
Physics, Nuclear and High Energy Physics, CNO cycle, Hydrogen, and linear accelerators - X- and γ-ray spectroscopy, collective, Extrapolation, chemistry.chemical_element, Alpha particle, Radiative capture - Hydrostatic stellar nucleosynthesis - Electrostatic, Nuclear physics, chemistry, Excited state, Nuclear astrophysics, Nuclear fusion, Atomic physics, Ground state
Abstract

In stars, four hydrogen nuclei are converted into a helium nucleus in two competing nuclear fusion processes, namely the proton-proton chain (p-p chain) and the carbon-nitrogen-oxygen (CNO) cycle. For temperatures above 20 million kelvin, the CNO cycle dominates energy production, and its rate is determined by the slowest process, the 14N(p,γ)15O radiative capture reaction. This reaction proceeds through direct and resonant capture into the ground state and several excited states in 15O. High energy data for capture into each of these states can be extrapolated to stellar energies using an R-matrix fit. The results from several recent extrapolation studies are discussed. A new experiment at the LUNA (Laboratory for Underground Nuclear Astrophysics) 400kV accelerator in Italy's Gran Sasso laboratory measures the total cross section of the 14N(p,γ)15O reaction with a windowless gas target and a 4π BGO summing detector, down to center of mass energies as low as 70keV. After reviewing the characteristics of the LUNA facility, the main features of this experiment are discussed, as well as astrophysical scenarios where cross section data in the energy range covered have a direct impact, without any extrapolation.

Published
2006

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