Results 1 - 10 of 12
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[en] The isobaric yield ratio difference (IBD) between two reactions of similar experimental setups is found to be sensitive to nuclear density differences between projectiles. In this article, the IBD probe is used to study the density variation in neutron-rich 48Ca. By adjusting diffuseness in the neutron density distribution, three different neutron density distributions of 48Ca are obtained. The yields of fragments in the 80A MeV 40,48Ca + 12C reactions are calculated by using a modified statistical abrasion-ablation model. It is found that the IBD results obtained from the prefragments are sensitive to the density distribution of the projectile, while the IBD results from the final fragments are less sensitive to the density distribution of the projectile. (orig.)
[en] The isoscaling and the isobaric yield ratio difference (IBD) probes, both of which are constructed by yield ratio of fragment, provide cancelation of parameters. The information entropy theory is introduced to explain the physical meaning of the isoscaling and IBD probes. The similarity between the isoscaling and IBD results is found, i.e., the information uncertainty determined by the IBD method equals to β – α determined by the isoscaling (α (β) is the parameter fitted from the isotopic (isotonic) yield ratio). (nuclear physics)
[en] A series of phenyl end-capped derivatives of benzo[d,d′]thieno[3,2-b;4,5- b′]dithiophene (BTDT) with periphery-fluorinated substitutions (PFS) were systematically investigated by using density functional theory (DFT) combined with the Marcus–Hush electron transfer theory. The substituting effects of PFS were discussed. Compared with the original compounds, (i) the PFS compounds have a relatively higher efficiency of charge transport, lower barriers of electron injection, and larger HOMO-LUMO gaps; (ii) the air-stability and the device performance are enhanced by PFS; and (iii) the HOMO-LUMO transitions in the absorption spectrum of the PFS compounds show an obvious blue-shift trend. The perfluorophenylbisbenzo[d, d′]thieno[3,2-b;4,5-b′]dithiophene (BpF-BTDT) is found to be the most stable and most effective compound in charge transport among the investigated compounds, and it is suggested as an ambipolar semiconducting material. The results of electronic coupling of the bisbenzo[d, d′]thieno[3,2-b; 4,5- b′]dithiophene (BBTDT) derivatives show that the orbital interaction is mainly contributed by the neighboring molecule in the two dimensional (2D) layer. The PFS compounds have lower oxidization potential, ionization potential, and electron affinity values than the corresponding original ones, which suggest that fluorination can enhance the performance of the thiophene-based organic solar cells. These findings provide a better understanding of the PFS effects on organic semiconductors and may help to design high-performance semiconductor materials. (paper)
[en] The properties of synthesized ambipolar organic semiconductor (OSC) materials, containing hydrogen bonding, i.e. the 6,6′-dibromoindigo and the three s-indaceno [1, 2-b:5, 6-b′] dithiophene-4,9-dione derivatives, have been systematically studied using a density functional theory. The hydrogen bonding formed between the interlayer molecules, though it does not affect the charge mobility in the same layer, influences the interorbital overlapping of HOMO and LUMO states between the layers, and influences the charge mobility directly. In addition, the hydrogen bonding between the layers may reinforce the π - π stacking and make the center-to-center distance closer, which indirectly enhances charge mobility, and can turn a monopole OSC into an ambipolar one. (paper)
[en] In the framework of a modified Fisher model, the ratio of the symmetry-energy coefficient to temperature (asym/T) is extracted from the fragment produced in the 124,136Xe induced reactions using the isobaric yield ratio methods based on different approximations. It is found that for nuclei with the same neutron excess (I≡N-Z) increases when the mass of the fragment increases, while for isobar asym/T decreases when I increases. It is also found that the extracted asym/T of the nucleus has very little dependence on the n/p ratio of the projectile, target, and the incident energies in the reaction. (orig.)
[en] In this study, the effects of the packing configuration and intermolecular interaction on the transport properties are investigated based on density functional theory. Molecular design from the standpoint of a quantum-chemical view is helpful to engender favorable molecular packing motifs. The transfer integral along the orientation with π–π overlap is much larger than other directions without π–π overlap, and the mobility along this orientation is higher than that along other directions. The intermolecular interaction analyses demonstrate that hydrogen bonds play a crucial role with strong electrostatic interactions in charge transfer. There will be a synergistic relationship when the π–π stacking and intermolecular interaction coexist in the same direction. It turns out that intermolecular interactions are responsible for charge transport, while π–π stacking interactions dominate donor–acceptor transport. Incorporating the understanding of the molecular packing motifs and intermolecular interactions into the design of organic semiconductors can assist in the development of novel materials.
[en] In this work, the charge transport properties of Isoindigo (II) and its derivatives which have the same hexyl chain were theoretically investigated by the Marcus-Hush theory combined with density functional theory (DFT). Here we demonstrate that the changes of benzene and thiophene groups in molecular structure have an important influence on the charge transport properties of organic semiconductor. The benzene rings of II are replaced by thiophenes to form the thienoisoindigo (TII), and the addition of benzene rings to the TII form the benzothienoisoindigo (BTII). The results show that benzene rings and thiophenes change the chemical structure of crystal molecules, which lead to different molecule stacking, thus, the length of hydrogen bond was changed. A shorter intermolecular hydrogen bond lead to tighter molecular stacking, which reduces the center-to-center distance and enhances the ability of charge transfer. At the same time, we theoretically demonstrated that II and BTII are the ambipolar organic semiconductor. BTII has better carrier mobility. The hole mobility far greater than electron mobility in TII, which is p-type organic semiconductor. Among all hopping path, we find that the distance of face-to-face stacking in II is the shortest and the electron-transport electronic coupling Ve is the largest, but II has not a largest anisotropic mobility, because the reorganization energy has a greater influence on the mobility than the electronic coupling. This work is helpful for designing ambipolar organic semiconductor materials with higher charge transport properties by introducing benzene ring and thiophene. Graphical abstract: .
[en] Isoscaling and isobaric yield ratio difference (IBD) methods are used to study Δμ/T (Δμ being the difference between the chemical potentials of the neutron and proton, and T being the temperature) in the measured 1 A GeV 124Sn + 124Sn, 112Sn + 112Sn, 136Xe + Pb and 124Xe + Pb reactions. The isoscaling phenomena in the 124Sn/112Sn and 136Xe/124Xe reaction pairs are investigated, and the isoscaling parameters α and β are obtained. The Δμ/T determined by the isoscaling method (IS-Δμ/T) and the IBD method (IB-Δμ/T) in the measured Sn and Xe reactions are compared. It is shown that in most fragments, the IS- and IB-Δμ/T are consistent in the Xe reactions, while the IS- and IB-Δμ/T ones are only similar in the less neutron-rich fragments in the Sn reactions. The shell effects in IB-Δμ/T are also discussed. (paper)
[en] A probe to extract the temperature (T_I_Y_R) from intermediate-mass fragment has been proposed using the isobaric yield ratio (IYR) difference based on the modified Fisher model. By analyzing the isobaric cross section in the measured 140A MeV "4"0","4"8Ca+"9Be reactions, the T_I_Y_R can well fit the IYR difference for the large mass fragments. Because of the fragments are produced in different colliding regions, it is also suggested to select the fragments according to different mechanisms when using T_I_Y_R. (paper)
[en] The FRACS parameterizations, labeled as FRACS-C, have been improved in order to predict the presence of isotopes near the proton drip line produced in projectile fragmentation reactions. By investigating the cross sections for proton-rich isotopes in a series of reactions with energies ranging from intermediate to relativistic, it is shown that the FRACS-C parameterizations can predict isotopes near the proton drip line considerably well. The FRACS-C parameterizations are suggested to serve as an effective tool for predicting the presence of proton-rich isotopes with large asymmetry in a projectile fragmentation reaction. Different reactions have been investigated to check these results.