Coherence effects in low energy Na*(3p)+Na+ scattering: Experiment and semiclassical calculations

Pronounced polarization effects have been observed in inelastic collisions of laser state-prepared Na^*(3p,M _L) with Na⁺ leading to Na^*(3d) for the energy rangeE _CM=20–45 eV. Using linearly polarized light the dependence of the inelastic process on the alignment of the electronic charge cloud of the Na^*(3p) prior to the collision has been measured. In studies with left and right hand circularly polarized light the angular momentum transferred in the collision process has been determined. The results are compared with similar data for the 3p→3s deexitation process studied previously [6]. The density matrix of the Na^*(3p) state has been evaluated with respect to the collisional excitation to Na^*(3d). Semiclassical calculations based on the coupled channel impact parameter approximation using pseudopotentials [7] and nonadiabatic rotational coupling elements for the Na ₂ ^* system [12] have been performed. The agreement with the experimental results is good, in particular for the higher collision energies.     

The Monohydrate of Basic Mercuric Nitrate, [Hg(OH)](NO3)(H2O)

Colourless single crystals of [Hg(OH)](NO₃)(H₂O) were obtained by slow evaporation of an aqueous solution of Hg(NO₃)₂ and Bi(NO₃)₃. The crystal structure (orthorhombic, Pbca, Z = 8, a = 943.2(2), b = 697.6(1), c = 1349.0(2) pm, R₁(all) = 0.0780) contains [Hg(OH)] = …OH–Hg–OH–Hg… zig zag chains (O–Hg–O angle: 168°, Hg–O–Hg angle: 112°, Hg–OH distance: 212 pm) to which one water molecule is attached loosely. The [Hg(OH)](H₂O) chains are connected via bis‐monodentate‐bridging nitrate ions to corrugated layers that are stacked in the [001] direction. Hg²⁺ has an effective 2+2+2(+1) coordination.     

Molecular beam scattering of NO+Ne: a joint theoretical and experimental study

The collision dynamics of the NO+Ne system is investigated in a molecular beam scattering experiment at a collision energy of 1055 cm(-1). Employing resonance enhanced multiphoton ionization of NO, we measured state-resolved integral and differential cross sections for the excitation to various levels of both spin-orbit manifolds. The dependence of the scattered intensity on the laser polarization is used to extract differential quadrupole moments for the collision induced angular momentum alignment. The set of cross section data is compared with results of a full quantum mechanical close coupling calculation using the set of ab initio potential energy surfaces of Alexander et al. [J. Chem. Phys. 114, 5588 (2001)]. In previous work, it was found that the positions and rotational substructures for the lowest bend-stretch vibrational states derived from these surfaces agree very well with the observed spectrum of the NO-Ne complex. For the same potential, we find that the calculated cross sections show a less satisfactory agreement with the experimental data. While the overall Jf dependence and magnitude of the integral and differential cross sections are in good agreement, noticeable discrepancies exist for the angle dependence of the differential cross sections. In general, the calculated rotational rainbow structures are shifted towards larger scattering angles indicating that the anisotropy of the potential is overestimated in the fit to the ab initio points or in the ab initio calculation itself. For most states, we find the measured alignment moments to be in excellent agreement with the results of the calculation as well as with predictions of sudden models. Significant deviations from the sudden models are observed only for those fine-structure changing collisions which are dominated by forward scattering. Results of the full quantum calculation confirm the deviations for these states.     

1.3-Benzodiphosphole, 1.2-bis-dimethylaminoalkylidenphosphino-benzen

The alkali phosphides of 1.2-bis-phosphinobenzene, and 1-alkyl-derivatives react with (Me₂N)₂COEt⁺BF₄^? to give the title compounds with dicoordinated phosphorus. The structure is proved by their nmr spectra.     

4-Aryldihydropyridines,a New Class of Highly Active Calcium Antagonists

The aryldihydropyridines first prepared by Hantzsch almost 100 years ago have recently been found to be highly effective calcium antagonists with suitable pharmacological profiles. An illustrative example is dimethyl-l,4-dihydro-2,6-dimethyl-4-(o-nitrophenyl)pyridine-3,5-dicarboxylate (Nifedipine) which is already employed therapeutically. This substance lowers the frequency of attack of angina pectoris and reduces blood pressure. The discovery of the therapeutic activity of this class of substances initiated renewed investigation of the Hantzsch condensation and the synthesis of numerous 4-aryldihydropyridines and related compounds. Qualitative and quantitative structure/activity relationships of these substances can be deduced from their biological data.     

Relaxometric study of copper [15]metallacrown-5 gadolinium complexes derived from alpha-aminohydroxamic acids

Proton nuclear magnetic relaxation dispersion (NMRD) profiles were recorded between 0.24 mT and 1.4 T for lanthanum(III)- and gadolinium(III)-containing [15]metallacrown-5 complexes derived from alpha-aminohydroxamic acids and with copper(II) as the ring metal. The influence of the different R-groups on the proton relaxivity was investigated, and a linear relationship between the relaxivity and the molecular mass of the metallacrown complex was found. The selectivity of the metallacrown complexes was tested by transmetalation experiments with zinc(II) ions. The crystal structure of the copper [15]metallacrown-5 gadolinium complex with glycine hydroximate ligands is reported.     

Die Struktur des Tetraphenyldisiloxans

Structure of Tetraphenyldisiloxane Tetraphenyldisiloxane 1 crystallizes at 298 K monoclinically (P2₁/n; a = 1407.6; b = 610.7; c = 1262.7 pm; β = 95.87° Z = 2) and undergoes a second order phase transition at 200 K, in an almost unchanged structure of triclinic symmetry. At 298 K the molecules are already bent (Si? O? Si = 160°) with static or dynamical disorder of the bridging atom. Both Si? O distances are different (156 or 169 pm), because the shift of the bridging O atom is not perpendicular to the Si? to? Si vector. The reason for this remarkable behavior is not yet clear. According to the vibrational spectra, the Si? O? Si bridge is bent in the crystal but, in CCl₄ solution a dynamical oscillation through the linear configuration may occur.