Direct fission versus sequential evaporation mechanism of sputtered caesium iodide cluster ions

A triple stage hybrid mass spectrometer was scanned for the trapping of the reaction intermediates of the over-all loss of two CsI-moieties from size-selected caesium iodide cluster ions of the general formula Cs (CsI)⁺ _n . In addition to appropriate MS/MS/MS-methods an electrically floated collision cell has been applied to trap intermediates of unimolecular and collision-induced evaporations. In comparison with other experimental findings the features of the evaporation mechanism are discussed.     

Theoretical implications involved in the DDRP method

The aim of this paper is to prove that safe success in finding reaction paths (RPs) can only be expected from global path-determining methods. Some extensions of the mathematical arguments leading to the introduction of the DDRP (dynamically defined reaction path) method have been sketched. Four cases involving relaxation of analyticity, variability of the gradient field, minimum energy (reaction) paths (MEPs) and golf pocket holes on the potential energy surface (PES), and the rather strange consequences of the main theorem of the DDRP method giving a rigorous mathematical basis to chemical intuition in reaction kinetics have been discussed. The discussions show that the DDRP method - when changing the conditions and parameters - may, in essence, involve all other global methods. It has been shown that the DDRP method works in a stable way even for non-analytic though smooth energy functions; moreover, the gradient field can be replaced by other vector fields resulting in better convergence to the reaction path. As a by-product, the question of the existence of MEPs can safely be handled and golf pocket holes are constructed on the PES in order to prove that local methods have chance to search faithfully the RPs in complicated systems only if the energy function can be restored from its arbitrarily small pieces.This work was presented in parts at the 8th International Congress of Quantum Chemistry, Prague, Czech Republic, June 19–23,1994; Addendum to the Book of Abstracts of the 8ICQC: P/I-129.     

Zu Struktur,Bindung und Ligandenaustauschverhalten von Nitrosyltechnetium(II)-Verbindungen Eine. EPR-Untersuchung

Structure, Bonding, and Ligand Exchange Behaviour of Nitrosyl-Technetium (II) Compounds. An EPR Study EPR investigations on the nitrosyltechnetium(II) compounds (Bu₄N)₂[Tc(NO)Cl₅], (Bu₄N)[Tc(NO)Br₄], (Bu₄N)[Tc(NO)I₄], and (Ph₄As)₂[Tc(NO)(NCS)₅] having a 4 t low-spin configuration are reported. The EPR parameters g?, Ã^Tc as well as ligand hyperfine data are used to analyze the bonding properties. The isotropic parameters g₀ and a are found to be clearly correlated to the composition of the coordination sphere. Therefore, they can be used to characterize mixed-ligand complexes unambiguously. The formation of mixed-ligand complexes was investigated for ligand-exchange reactions on [Tc(NO)Cl₅]^2? and [Tc(NO)Br₄]^?. In these investigations unsaturated dichalcogeno ligands are included.     

An algorithm for determining dynamically defined reaction paths (DDRP)

Summary A numerically stable and well-parallelizable curve variational algorithm is described for determining tangent curves of vector fields between two given stationary points. In particular, the method is suitable for finding reaction paths and saddle points on potential energy hypersurfaces (PHS). The stability of the procedure is illustrated by an artificial mathematical function, showing phases of following the reaction on the PHS.Dedicated to Professor Zoltán G. Szabó, the great teacher and scientist in reaction kinetics and in many other fields of physical chemistry, on his 84th birthday.     

SOCl2 and POCl3 as reducing agents for TcO 4 − formation and EPR detection of Tc(VI)-compounds

Pertechnetate, TcO ₄ ^– , is reduced by thionyl chloride and phosphoryl chloride, respectively, to yield semistable Tc(VI) intermediates which can easily be detected by EPR spectroscopy. Spectra are recorded in liquid and frozen solutions. EPR data as well as chemical behaviour suggest the compounds obtained to be oxochloro complexes of technetium(VI).     

“Comment” on the Reply to the Paper “On the Elber–Karplus Reaction Path-Following Method and Related Procedures”

The flaws in the Reply [1] to our paper [2] have been pointed out. Elber and Karplus (EK) have not disproved our irrefutable global statement that the energy average cannot be minimized which rebuts the theoretical background of EK-type calculations. Another statement of ours has shown that even a curve for which the average energy is locally minimal for all directional perturbations in the sense of classical variational calculus cannot be identical with the reaction path (RP) defined as a steepest descent path (SDP). EK found an error in the early preprint of our theoretical paper [3] and because of this error they qualified our correct variational statement as false for all the SDPs consisting of a straight line each. Mixing global and variational arguments, EK refuted our criticism in a logically incorrect manner. In this Comment we prove that both of our earlier statements invariably remain in force and the criticism included in those has been as well-established and solid as was before.     

Influence of Cycle Temperatures on the Thermochemical Heat Storage Densities in the Systems Water/Microporous and Water/Mesoporous Adsorbents

The adsorption equilibrium of water on microporous adsorbents (zeolites of NaA-, NaY- and NaX-type as well as their ion exchanged forms) and on mesoporous adsorbents (different silica gels and composite material i.e. silica gel + salt hydrate) has been studied experimentally and theoretically. Using the Dubinin theory of pore filling the characteristic curves of the adsorption systems and other relevant dependences such as isotherms, isobars, isosteres and the curve of the differential heat of adsorption were calculated. For all systems investigated the adsorption were calculated. A_ads and the desorption potential A_des of the closed heat storage system were estimated. These values define the working range of the adsorption/desorption cycle and allow to calculate the specific heat storage density Δ h_sp. On the basis of Δ h_sp the different adsorbents were compared in order to select the optimal porous storage material for a given application. The presented experimental and theoretical investigations show that the adsorption systems water-zeolite and water-composites are promising working pairs for thermochemical heat storage processes for hot tap water supply and space heating of single family dwellings. The advantage of the water-composite system is the low desorption temperature (solar energy) the main shortcoming the low temperature lift. The advantage of the water zeolite system is the high temperature lift, the shortcoming are the relative high desorption temperatures.     

Die elektrochemische Reduktion von CSSe und CSe2 in Dimethylformamid: Heterocyclische 1,2-Dichalkogenolate und ihre Koordinationschemie

Electrochemical Reduction of CSSe and CSe₂ in Dimethylformamide: Heterocyclic 1,2-Dichalcogenolates and their Coordination Chemistry Starting from carbon diselenide or carbon selenidesulfide the electrochemical preparation (electrosynthesis) of heterocyclic dichalcogenolates C₃X₅^2? (X = Se: dsis; X = S/Se: C₃S_xSe_y^2?) is outlined. The 1,2-dichalcogenolate compounds were isolated and characterized as dibenzoyl derivatives. Bis- or tris-chelates of general type A_m[M(C₃X₅)_n] (with A = Bu₄N⁺, Ph₄As⁺; M = Zn^II, Pt^II, Pd^II, Ni^III, Cu^III, Au^III, In^III; X = Se, S/Se; m = 1, 2, 3; n = 2, 3, respectively) are available directly from methanolic solutions of the dibenzoylates after hydrolytic cleavage of the latter with sodium methanolate. In addition bis-chelates Bu₄N[Ni(C₃X₅)₂] (X = Se, S/Se) have been characterized by cyclovoltammetry and epr spectroscopy and compared with the corresponding all-sulfur ligand compound Bu₄N[Ni(dmit)₂] (X = S). Arguments are given for the fact that the allselenium ligand dsis (X = Se) yields the Cu^III or Ni^III chelate at once whereas with dmit using identical conditions the metal(II) compounds are formed.     

On fixed points of holomorphic automorphisms

Summary Banach M-lattices are studied from the view point whether all the biholomorphic automorphisms of their unit balls admit fixed points when continuously extended to the closure of the unit ball. A characterization of compact topologieal F-spaces is found in terms of the fixed points of the elements of AutB(C()) which enables to establish some particular properties also of the topological automorphisms of compact F-spaces. Finally it is shown that if the M- lattice E admits a predual then each member of Aut B(E) has fixed point if and only if E is isometrically isomorphic with some l-space.