Structural Integration of Tellurium Oxide into Mixed-Network-Former Glasses: Connectivity Distribution in the System NaPO3–TeO2

FSodium phosphate tellurite glasses in the system (NaPO3)(x)(TeO2)(1-x) were prepared and structurally characterized by thermal analysis, vibrational spectroscopy, X-ray photoelectron spectroscopy (XPS) and a variety of complementary solid-state nuclear magnetic resonance (NMR) techniques. Unlike the situation in other mixed-network-former glasses, the interaction between the two network formers tellurium oxide and phosphorus oxide produces no new structural units, and no sharing of the network modifier Na2O takes place. The glass structure can be regarded as a network of interlinked metaphosphate-type P(2) tetrahedral and TeO4/2 antiprismotic units. The combined interpretation of the O 1s XPS data and the P-31 solid-state NMR spectra presents clear quantitative evidence for a nonstatistical connectivity distribution. Rather the formation of homootomic P-O-P and Te-O-Te linkages is favored over mixed P-O-Te connectivities. As a consequence of this chemical segregation effect, the spatial sodium distribution is not random, as also indicated by a detailed analysis of P-31/No-23 rotational echo double-resonance (REDOR) experiments. ACHTUNGTRENUNG(TeO2)1 x were prepared and structurally characterized by thermal analysis,vibrat ional spectroscopy,X-ray photoelectron spectroscopy (XPS) and a variety of complementary solid-state nuclear magnetic resonance (NMR) techniques. Unlike the situation in other mixed-network-former glasses,the interaction between the two network formers tellurium oxide and phosphorus oxide produces no new structural units,and no sharing of the network modifier Na2O takes place. The glass structure can be regarded as a network of interlinked metaphosphate-type P(2) tetrahedral and TeO4/2 antiprismatic units. The combined interpretation of the O 1s XPS data and the 31P solid-state NMR spectra presents clear quantitative evidence for a nonstatistical connectivity distribution. Rather,the formation of homoatomic P O P and Te O Te linkages is favored over mixed P O Te connectivities. As a consequence of this chemical segregation effect,the spatial sodium distribution is not random,as also indicated by a detailed analysis of 31P/23Na rotational echo double-resonance (REDOR) experiments.

Quark distributions in nuclei and nuclear effects on nucleon structure functions

Extended quark distribution functions are presented obtained by fitting a large amount of experimental data of the l-A DIS process on the basis of an improved nuclear density model. The experimental data of l-A DIS processes with A >= 3 in the region 0.0010 <= x <= 0.9500 axe quite satisfactorily described by using the extended formulae. Our knowledge of the influence of nuclear matter on the quark distributions is deepened.

Di-nuclear systems studied with the velocity filter SHIP

Various nuclear reactions like quasi-fission, fusion-fission or particle and cluster evaporation from excited compound nuclei were studied in heavy-ion reactions at the velocity filter SHIP of GSI. The velocity filter offers the possibility to detect all reaction products under zero degree relative to the beam direction. Together with the measurement of the product velocity distribution this allows for an identification of the underlying reaction mechanism. This article is focussed on reactions of Mg-25 and Ni-64 beams on Pb-206,Pb-207 targets at energies of 5.9 x A MeV and 8.7 x A MeV. Besides evaporation residues from Mg-25 + Pb-206 collisions we found evidence for rotation and quasi-fission of nuclear molecules formed in the entrance channel after the capture stage. The break-up of the systems showed a preferred clustering leading to isotopes in the region 84 <= Z <= 88 and 122 <= N <= 127 of the chart of nuclei.

Isospin effect in the nuclear reaction induced by neutron-halo nuclei

We study the average property of the isospin effect of reaction induced by halo-neutron nuclei He-8 and He-10 in the intermediate energy heavy ion collisions using the isospin-dependent quantum molecular dynamics model (IQMD). This study is based on the extended neutron density distribution for the halo-neutron nuclei, which includes the average property of the isospin effect-of reaction mechanism and loose inner structure. The extended neutron density distribution brings an important isospin. effect into the average property of reaction mechanism because the interaction potential and nucleon-nucleon(N-N) cross section in IQMD model depend sensitively on the density distribution of colliding system. In order to see clearly the average properties of reaction mechanism induced by halo-neutron nuclei we also compare the results for the neutron-halo colliding systems with those for the corresponding stable colliding systems under the same incident channel condition. We found that the extended density distribution for the neutron-halo projectile brings an important isospin effect to the reaction mechanism, which leads to the decrease of nuclear stopping R, yet induces obvious increase of the neutron-proton ratio of nucleon emissions and isospin fractionation ratio for all beam energies studied in this work, compared to the corresponding stable colliding system. In this case, nuclear stopping, the neutron-proton ratio of nucleon emissions and isospin fractionation ratio induced by halo-neutron nuclei can be used as possible probes for studying the average property of the isospin effect of reaction mechanism and extracting the information of symmetry potential and in-medium N-N cross section by the neutron-halo nuclei in heavy ion collisions.

Probing the symmetrical potential in nuclear reaction iinduced by neutron-halo nuclei

In terms of the isospin-dependent quantum molecular dynamics model (IQMD), important isospin effect in the halo-neutron nucleus induced reaction mechanism is. investigated, and consequently, the symmetrical potential form is extracted in the intermediate energy heavy ion collision. Because the interactive potential and in-medium nucleon-nucleon (N-N) cross section in the IQMD model sensitively depend on the density distribution of the colliding system, this type of study is much more based on the extended density distribution with a looser inner nuclear structure of the halo-neutron nucleus. Such a density distribution includes averaged characteristics of the isospin effect of the reaction mechanism and the looser inner nuclear structure. In order to understand clearly the isospin effect of the halo-neutron nucleus induced reaction mechanism, the effects caused by the neutron-halo nucleus and by the stable nucleus with the same mass are compared under the same condition of the incident channel. It is found that in the concerned beam energy region, the ratio of the emitted neutrons and protons and the ratio of the isospin fractionations in the neutron-halo nucleus case are considerably larger than those in the stable nucleus case. Therefore, the information of the symmetry potential in the heavy ion collision can be extracted through such a procedure.