Dipole blockade at Förster resonances in high resolution laser excitation of Rydberg states of cesium atoms

High resolution laser excitation of np Rydberg states of cesium atoms shows a dipole blockade at F?rster resonances corresponding to the resonant dipole-dipole energy transfer of the np+np --> ns+(n+1)s reaction. The dipole-dipole interaction can be tuned on and off by the Stark effect, and such a process, observed for relatively low n(25-41), is promising for quantum gate devices. Both Penning ionization and saturation in the laser excitation can limit the range of observation of the dipole blockade.     

EPR and DFT studies of the one-electron reduction product of phospholium cations

Cyclic voltammetry and EPR spectroscopy show that cationic phospholium groups are good electron acceptors whose reduction leads to a neutral radical where the unpaired electron is mainly delocalized on the carbon atoms of the five-membered ring. DFT calculations together with the crystal structure of phospholiums indicate that the electron addition causes a drastic diminution of the exocyclic CPC angle. The SOMO of reduced phospholium is compared to the SOMO of the phosphole radical anion.     

Scalarization of Tangential Regularity of Set-Valued Mappings

A set-valued mapping M from a topological vector space E into a normed vector space F is tangentially regular at a point in its graph g p h M if the Clarke tangent cone to g p h M at is equal to the Bouligand contingent cone to g p h M at . In this paper we characterize, in several cases, this tangential regularity as the directional regularity of the scalar function _M defined by _M (x, y) : = d(y, M(x)). The results allow us to express, in a useful formula, the subdifferential of _M in terms of the normal cone to the graph of M.     

Convex composite functions in Banach spaces and the primal lower-nice property

Primal lower-nice functions defined on Hilbert spaces provide examples of functions that are ``integrable' (i.e. of functions that are determined up to an additive constant by their subgradients). The class of primal lower-nice functions contains all convex and lower- functions. In finite dimensions the class of primal lower-nice functions also contains the composition of a convex function with a mapping under a constraint qualification. In Banach spaces certain convex composite functions were known to be primal lower-nice (e.g. a convex function had to be continuous relative to its domain). In this paper we weaken the assumptions and provide new examples of convex composite functions defined on a Banach space with the primal lower-nice property. One consequence of our results is the identification of new examples of integrable functions on Hilbert spaces.

     

Collision cross sections, pressure-broadening coefficients and second virial coefficients for the acetylene-argon complex: experiments and calculations on a new potential energy surface

Integral cross sections and pressure-broadening coefficients have been measured by molecular beam scattering and by high-resolution infrared spectroscopy, respectively, for the acetylene-argon system. A new potential energy surface (PES) is proposed to describe structure and dynamical properties of this prototypical weakly bound complex. The PES has been parametrized exploiting a novel atom-bond pairwise additive scheme and has been fitted to the experimental data. Calculations of the scattering cross sections (both differential and integral), pressure-broadening, and second virial coefficients have been performed using both the present and also the most recent ab initio PES available in the literature. Analysis of the new experimental data indicates that the anisotropy of the interaction in the well region should be larger than that obtained in ab initio calculations. This is also in line with previous spectroscopic results.     

Den Einfluss des arabischen Gummis auf gewisse Reactionen

Ohne Zusammenfassung     

High-precision masses of 29-33Mg and the N = 20 shell “closure”

High-precision mass measurements have been performed on the exotic magnesium isotopes ^29-33Mg using the MISTRAL radiofrequency spectrometer, especially suited for very short-lived nuclides. This method, combined with the powerful tool of resonant laser ionization at ISOLDE, has provided a significant reduction of uncertainty for the masses of the most exotic Mg isotopes: a relative error of 7×10^-7 was achieved for the weakly produced ³³Mg that has a half-life of only 90ms. Moreover, the mass of ³³Mg is found to change by over 250keV. Verifying and minimizing binding energy uncertainties in this region of the nuclear chart is important for understanding the lack of binding energy that is normally associated with magic numbers.     

Molecular-beam scattering and pressure broadening cross sections for the acetylene-neon system

Integral cross sections and pressure broadening coefficients have been measured for the acetylene — neon system by a molecular beam scattering technique and by high infrared resolution spectroscopy, respectively. We have performed quantal calculations using an ab-initio potential energy surface (PES) [J. Chem. Phys. 109, 8968 (1998)]. Results are found to be in good agreement with both measured integral cross sections and pressure broadening coefficients for the two temperatures investigated (173 and 298 K). We have also derived a semi-empirical PES parameterized using an atom-bond pairwise additive scheme. This PES shows an isotropic component in agreement with the ab-initio calculation, reproduces the scattering data but it only leads to a reasonable agreement for the pressure broadening coefficients.     

Specific photodissociation of peptides with multi-stage mass spectrometry

We report collision-induced dissociation (CID) and laser-induced dissociation (LID) performed at different wavelengths between 220 and 280 nm of the peptides leucine-enkephalin (protonated) and gramicidin A (sodiated). Hydrogen-atom losses and side-chain cleavages were observed in LID experiments. These losses depend on the laser wavelength and lead to the formation of radical ions. The fragmentations of these radicals, which are not observed in CID experiments, were investigated in multi-stage mass spectrometry experiments.