Photoproduction ofN = (1236) by polarized γ-Quanta

The one-pion-exchange model with gauge invariant extension is used to calculate cross sections and decay distributions for the reactionγp→N⁼⁺⁺ π ^? where theγ-quanta are linearly polarized. We show that measurements with polarizedγ-quanta would provide a sensitive check of the model. In particular, the relevance of the terms added to the one-pion-exchange part to guarantee gauge invariance could be tested.     

Radiative decay of benzophenone low pressure gas

The radiative decay of benzophenone low pressure gas was studied subsequent to pulse excitation at several wavelengths. Estimates of the emission rates and quantum yields for the fast and slow decay processes lead to models for the isolated molecule radiationless processes; both somewhat different from that recently proposed by Busch et al. We propose that it is the very rapid intersystem crossing process that produces the non-stationary mixed singlet-triplet levels.     

Halogenation of fluorinated cyclic 1,3-dicarbonyl compounds: new aspects of synthetic application

In order to elaborate on an approach towards 2-(fluoroacyl)phenols being the superior alternative to the conventional Fries-rearrangement based methodology, the behaviour of cyclic fluorinated 1,3-dicarbonyls in reactions with halogenating agents was examined. The synthetic relevance of the polyhalogenated compounds obtained was demonstrated by the synthesis of several new heterocycles. An aromatization via a halogenation-dehydrohalogenation sequence proved to be a rewarding synthetic route to 2-(fluoroacyl)phenols and previously unknown 3-(fluoroacyl)thiochromones. The structure of one of the synthesized compounds was confirmed by X-ray diffraction analysis.     

EuI2, a low‐temperature europium(II) iodide phase

Light‐yellow europium(II) diiodide, prepared by the low‐temperature reaction of europium and ammonium iodide in liquid ammonia at 200 K and characterized by high‐resolution X‐ray powder diffraction, represents a new phase for EuI₂ that adopts an orthorhombic Pnma structure with all three atoms lying on 4c positions (.m.). It is isotypic with SrI₂(IV). Temperature‐dependent X‐ray measurements performed to investigate the thermal stability of the new phase show that it decomposes irreversibly to amorphous material around 673 K. Total‐energy density‐functional calculations using the generalized gradient approximation suggest this to be the ground‐state structure of EuI₂.     

Flat histogram methods for quantum systems: algorithms to overcome tunneling problems and calculate the free energy

We present a generalization of the classical Wang-Landau algorithm [Phys. Rev. Lett. 86, 2050 (2001)]] to quantum systems. The algorithm proceeds by stochastically evaluating the coefficients of a high temperature series expansion or a finite temperature perturbation expansion to arbitrary order. Similar to their classical counterpart, the algorithms are efficient at thermal and quantum phase transitions, greatly reducing the tunneling problem at first order phase transitions, and allow the direct calculation of the free energy and entropy.