Multiple recapture of electrons in multiple ionization of the argon dimer by a strong laser field

We observe multiply frustrated tunneling ionization-induced dissociation of the argon dimers by intense linearly polarized ultrashort laser pulses. By measuring the kinetic energy release and angular distribution of the Coulomb explosion of up to eightfold ionized argon dimers, we can trace the recapture of up to two electrons to Rydberg states of the highly charged compound at the end of the laser pulse. Upon dissociation of the dimer, the Rydberg electron prefers to localize at the atomic ion with the higher charge state. We probe the electron recapture dynamics by a time-delayed weak pulse.     

The Impact of Leaving Group Anomericity on the Structure of Glycosyl Cations of Protected Galactosides

It has been reported that fragments produced by glycosidic bond breakage in mass spectrometry-based experiments can retain a memory of their anomeric configuration, which has major implications for glycan sequencing. Herein, we use cryogenic vibrational spectroscopy and ion mobility-mass spectrometry to study the structure of B-type fragments of protected galactosides. Cationic fragments were generated from glycosyl donors carrying trichloroacetimidate or thioethyl leaving groups of different anomeric configuration. The obtained infrared signatures indicate that the investigated fragments exhibit an identical structure, which suggests that there is no anomeric memory in B-type ions of fully protected monosaccharides.     

Polynomial interpolation of cryptographic functions related to Diffie-Hellman and discrete logarithm problem

Recently, the first author introduced some cryptographic functions closely related to the Diffie-Hellman problem called P-Diffie-Hellman functions. We show that the existence of a low-degree polynomial representing a P-Diffie-Hellman function on a large set would lead to an efficient algorithm for solving the Diffie-Hellman problem. Motivated by this result we prove lower bounds on the degree of such interpolation polynomials. Analogously, we introduce a class of functions related to the discrete logarithm and show similar reduction and interpolation results.     

Results on two-, three-, and four-body events from the100Mo+100Mo and120Sn+120Sn collisions aroundE/A=20 MeV

Events with 2, 3 and 4 heavy-fragments (A≧20) have been detected in the reactions¹⁰⁰Mo+¹⁰⁰Mo atE/A =18.7, 23.7 MeV and¹²⁰Sn+¹²⁰Sn atE/A=18.4 MeV. The experiments were performed with an array of 12 detectors which together covered a large fraction of the forward hemisphere and allowed a high detection efficiency for these events. Masses and energies of all fragments have been reconstructed by means of an improved version of the kinematic coincidence method. The probabilitiesP ₃ andP ₄ of producing 3- and 4-body events were found to depend mainly on the dissipated energy rather than on the bombarding energy, thus indicating that their origin lies more in the decay properties of the excited fragments than in the dynamics of the interaction. Emission of light particles from the composite system is shown to become more relevant with increasing bombarding energy and may explain the drop of theP ₃ andP ₄ curves at high energy losses. Small deviations of theP ₃ andP ₄ curves at 23.7A · MeV from those at lower bombarding energies were used to estimate the amount of a possible pre-equilibrium light particle emission as a function of impact parameter.     

Another approach to proof: Arguments from physics

In the first part of the paper we will explore the use of arguments from physics in mathematical proof and give some reasons why this approach might be worthwhile. In the second part we will relate this idea to Freudenthal's concept of local organization. The third part of the paper will present the results of an empirical study conducted in Canada on the classroom use of arguments from physics in mathematical proof.     

Synthesis and reaction of secondary and primary diorganozinc reagents using a boron–zinc exchange reaction: A useful method for the stereo- and regioselective formation of new carbon---carbon bonds

Applications of the boron–zinc exchange reaction to make new carbon---carbon bonds are reviewed. Functionalized chiral secondary alkylzinc reagents can be prepared by this exchange reaction and allows to perform formal enantioselective Michael-additions with umpolung of reactivity. The scope of substrate controlled diastereoselective hydroborations can be considerably enhanced by this methodology. A chemoselective approach to difunctionalized arylsilanes is also described.     

3D‐Printing inside the Glovebox: A Versatile Tool for Inert‐Gas Chemistry Combined with Spectroscopy

3D‐Printing with the well‐established ‘Fused Deposition Modeling’ technology was used to print totally gas‐tight reaction vessels, combined with printed cuvettes, inside the inert‐gas atmosphere of a glovebox. During pauses of the print, the reaction flasks out of acrylonitrile butadiene styrene were filled with various reactants. After the basic test reactions to proof the oxygen tightness and investigations of the influence of printing within an inert‐gas atmosphere, scope and limitations of the method are presented by syntheses of new compounds with highly reactive reagents, such as trimethylaluminium, and reaction monitoring via UV/VIS, IR, and NMR spectroscopy. The applicable temperature range, the choice of solvents, the reaction times, and the analytical methods have been investigated in detail. A set of reaction flasks is presented, which allow routine inert‐gas syntheses and combined spectroscopy without modifications of the glovebox, the 3D‐printer, or the spectrometers. Overall, this demonstrates the potential of 3D‐printed reaction cuvettes to become a complementary standard method in inert‐gas chemistry.     

Interactive simulation of aircraft noise in aural and visual virtual environments

This paper describes a novel aircraft noise simulation technique developed at RWTH Aachen University, which makes use of aircraft noise auralization and 3D visualization to make aircraft noise both heard and seen in immersive Virtual Reality (VR) environments. This technique is intended to be used to increase the residents’ acceptance of aircraft noise by presenting noise changes in a more directly relatable form, and also aid in understanding what contributes to the residents’ subjective annoyance via psychoacoustic surveys. This paper describes the technique as well as some of its initial applications. The reasoning behind the development of such a technique is that the issue of aircraft noise experienced by residents in airport vicinities is one of subjective annoyance. Any efforts at noise abatement have been conventionally presented to residents in terms of noise level reductions in conventional metrics such as A-weighted level or equivalent sound level L_eq. This conventional approach however proves insufficient in increasing aircraft noise acceptance due to two main reasons – firstly, the residents have only a rudimentary understanding of changes in decibel and secondly, the conventional metrics do not fully capture what the residents actually find annoying i.e. characteristics of aircraft noise they find least acceptable. In order to allow least resistance to air-traffic expansion, the acceptance of aircraft noise has to be increased, for which such a new approach to noise assessment is required.     

Heterocyclic carbenes: synthesis and coordination chemistry

The chemistry of heterocyclic carbenes has experienced a rapid development over the last years. In addition to the imidazolin-2-ylidenes, a large number of cyclic diaminocarbenes with different ring sizes have been described. Aside from diaminocarbenes, P-heterocyclic carbenes, and derivatives with only one, or even no heteroatom within the carbene ring are known. New methods for the synthesis of complexes with N-heterocyclic carbene ligands such as the oxidative addition or the metal atom template controlled cyclization of beta-functionalized isocyanides have been developed recently. This review summarizes the new developments regarding the synthesis of N-heterocyclic carbenes and their metal complexes.     

Desymmetrization of an Octahedral Coordination Complex Inside a Self‐Assembled Exoskeleton

The synthesis of a centrally functionalized, ribbon‐shaped [6]polynorbornane ligand L that self‐assembles with Pd^II cations into a {Pd₂ L ₄} coordination cage is reported. The shape‐persistent {Pd₂ L ₄} cage contains two axial cationic centers and an array of four equatorial H‐bond donors pointing directly towards the center of the cavity. This precisely defined supramolecular environment is complementary to the geometry of classic octahedral complexes [M(XY)₆] with six diatomic ligands. Very strong binding of [Pt(CN)₆]^2? to the cage was observed, with the structure of the host–guest complex {[Pt(CN)₆]@Pd₂L₄} supported by NMR spectroscopy, MS, and X‐ray data. The self‐assembled shell imprints its geometry on the encapsulated guest, and desymmetrization of the octahedral platinum species by the influence of the D_4h‐symmetric second coordination sphere was evidenced by IR spectroscopy. [Fe(CN)₆]^3? and square‐planar [Pt(CN)₄]^2? were strongly bound. Smaller octahedral anions such as [SiF₆]^2?, neutral carbonyl complexes ([M(CO)₆]; M=Cr, Mo, W) and the linear [Ag(CN)₂]^? anion were only weakly bound, showing that both size and charge match are key factors for high‐affinity binding.