Properties of nearly one-electron molecules. I. An iterative Green function approach to calculating the reaction matrix

An ab initio R-matrix method for determining the molecular reaction matrix of scattering theory is introduced. The method makes use of a principal-value Green function to compute the collision channel wave functions for the scattered electron, in combination with the Kohn variational scheme for the evaluation of R-matrix eigenvalues on a spherical boundary surface at short range. This technique permits the size of the bounded volume in the variational calculation to be reduced, making the computations fast and efficient. The reaction matrix is determined in a form that minimizes its energy dependence. Thus the procedure does not require modification or an increase in the computational effort to study the electronic structure and dynamics in Rydberg molecules with extremely polar ion cores. The analysis is specialized to examine the bound-state and free-electron scattering properties of nearly one-electron molecular systems, which are characterized by a Rydberg/scattering electron incident on a closed-shell ion core. However, it is shown that the treatment is compatible with all-electron/ab initio representations of open-shell and nonlinear polyatomic ion cores, emphasizing its generality. The introduced approach is used to calculate the electronic spectrum of the calcium monofluoride molecule, which has the extremely polar (Ca+2F-)+e- closed-shell ion-core configuration. The calculation utilizes an effective single-electron potential determined by M. Arif, C. Jungen, and A. L. Roche [J. Chem. Phys. 106, 4102 (1997)] previously. Close agreement with experimental data is obtained. The results demonstrate the practical utility of this method as a viable alternative to the standard variational approaches.     

Ein Verfahren zur quantitativen Trrennung von Platin und Iridium

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Chemoenzymatic Synthesis of Fluorinated Cellodextrins Identifies a New Allomorph for Cellulose-Like Materials**

Understanding the fine details of the self-assembly of building blocks into complex hierarchical structures represents a major challenge en route to the design and preparation of soft-matter materials with specific properties. Enzymatically synthesised cellodextrins are known to have limited water solubility beyond DP9, a point at which they self-assemble into particles resembling the antiparallel cellulose II crystalline packing. We have prepared and characterised a series of site-selectively fluorinated cellodextrins with different degrees of fluorination and substitution patterns by chemoenzymatic synthesis. Bearing in mind the potential disruption of the hydrogen-bond network of cellulose II, we have prepared and characterised a multiply 6-fluorinated cellodextrin. In addition, a series of single site-selectively fluorinated cellodextrins was synthesised to assess the structural impact upon the addition of one fluorine atom per chain. The structural characterisation of these materials at different length scales, combining advanced NMR spectroscopy and microscopy methods, showed that a 6-fluorinated donor substrate yielded multiply 6-fluorinated cellodextrin chains that assembled into particles presenting morphological and crystallinity features, and intermolecular interactions, that are unprecedented for cellulose-like materials.     

强磁场对熔融织构GdBCO块材中Gd_2BaCuO_5颗粒的取向作用

在GdBCO超导块材的熔融织构生长过程中施加10T强磁场,通过SEM研究强磁场对Gd2BaCuO5(Gd211)颗粒的影响.研究发现棒状Gd211颗粒在强磁场的作用下发生了择优取向——Gd211颗粒的长边与磁场方向平行.延长样品处于熔融状态的时间,发现Gd211颗粒的取向性明显增加.通过分析熔融织构的相变过程,结合磁取向能的公式,讨论了取向性增加的原因.同时,探讨了Gd211颗粒的择优取向对样品的超导性能产生的影响.     

Observation of ultrahigh-energy cosmic rays with the ANITA balloon-borne radio interferometer

We report the observation of 16 cosmic ray events with a mean energy of 1.5 × 101? eV via radio pulses originating from the interaction of the cosmic ray air shower with the Antarctic geomagnetic field, a process known as geosynchrotron emission. We present measurements in the 300-900 MHz range, which are the first self-triggered, first ultrawide band, first far-field, and the highest energy sample of cosmic ray events collected with the radio technique. Their properties are inconsistent with current ground-based geosynchrotron models. The emission is 100% polarized in the plane perpendicular to the projected geomagnetic field. Fourteen events are seen to have a phase inversion due to reflection of the radio beam off the ice surface, and two additional events are seen directly from above the horizon. Based on a likelihood analysis, we estimate angular pointing precision of order 2° for the event arrival directions.     

Diagnostic techniques in deflagration and detonation studies

Abstract

Advances in experimental, high-speed techniques can be used to explore the processes occurring within energetic materials. This review describes techniques used to study a wide range of processes: hot-spot formation, ignition thresholds, deflagration, sensitivity and finally the detonation process. As this is a wide field the focus will be on small-scale experiments and quantitative studies. It is important that such studies are linked to predictive models, which inform the experimental design process. The stimuli range includes, thermal ignition, drop-weight, Hopkinson Bar and Plate Impact studies. Studies made with inert simulants are also included as these are important in differentiating between reactive response and purely mechanical behaviour.

Graphical abstract

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Metastable anions of dinitrobenzene: resonances for electron attachment and kinetic energy release

Attachment of free, low-energy electrons to dinitrobenzene (DNB) in the gas phase leads to DNB(-) as well as several fragment anions. DNB(-), (DNB-H)(-), (DNB-NO)(-), (DNB-2NO)(-), and (DNB-NO(2))(-) are found to undergo metastable (unimolecular) dissociation. A rich pattern of resonances in the yield of these metastable reactions versus electron energy is observed; some resonances are highly isomer-specific. Most metastable reactions are accompanied by large average kinetic energy releases (KER) that range from 0.5 to 1.32 eV, typical of complex rearrangement reactions, but (1,3-DNB-H)(-) features a resonance with a KER of only 0.06 eV for loss of NO. (1,3-DNB-NO)(-) offers a rare example of a sequential metastable reaction, namely, loss of NO followed by loss of CO to yield C(5)H(4)O(-) with a large KER of 1.32 eV. The G4(MP2) method is applied to compute adiabatic electron affinities and reaction energies for several of the observed metastable channels.     

Dinuclear alkynyllanthanoid(II) dications with pentaphenylcyclopentadienyl or tri-tert-butyldiphosphacyclopentadienyl counter ions

Reaction of [Yb(CpPh5)(C[triple bond]CPh)(thf)]2 (CpPh5 = pentaphenylcyclopentadienyl), prepared from Yb(C triple bond CPh)2 and HCpPh5 or Yb metal, HgPh(C[triple bond]CPh) and HCpPh5, with a controlled amount of diglyme (dig), and of Eu(C triple bond CPh)2, P triple bond CBut and dig, yield the unusual organolanthanoid(II) dicationic complexes [Yb(C[triple bond]CPh)(dig)(thf)2]2[CpPh5]2.4thf and [Eu(C triple bond CPh)(dig)2]2[P2C3But3]2 respectively.