One-nucleon transfer reactions in the12C+12C system at 344.5 MeV

Angular distributions of cross sections have been measured for single nucleon transfer reactions induced by 344.5 MeV¹²C ions on a¹²C target. DWBA analyses have been performed for transitions to discrete final states. Spectroscopic information has been derived and is compared with results of other studies.     

Interpenetrating nets in cis‐bis­(pyri­dine‐4‐carboxyl­ate)­nickel(II)

The title compound, [Ni(C₆H₄NO₂)₂], crystallized in a three‐dimensional framework consisting of three interpenetrating diamond‐like nets. The Ni atom is on a twofold axis, the coordination is `(O₂)₂N₂' in a cis arrangement and the ligands are bridging.     

Reductive couplings with low-valent titanium compounds (McMurry Reaction). An e.s.r. investigation into the TiCl3/LiAlH4/ROH system

Summary A model is discussed for the titanium species, [M], used in reductive couplings (McMurry Synthesis). Evidence is given for the presence of aluminium(0) in [M], generated in the TiCl₃/LiAlH₄ system. Reactions of this [M] with alcohols showinter alia titanium(III) signals with superimposed Al-splittings in the e.s.r. spectra, thus proving the existence of mixed Ti-Al complexes in the TiCl₃/LiAlH₄/ROH system.On leave from Polish Academy of Sciences, Institute of Organic Chemistry, Kasprzaka 44/52, Warszawa, Poland.     

PHOTOELECTRON QUANTUM YIELDS AND PHOTOELECTRON MICROSCOPY OF CHLOROPHYLL AND CHLOROPHYLLIN

Abstract— The absolute PE quantum yield curves of chls a and b ,.chin, and phytol were examined over the wavelength range 500-180 nm. In the long wavelength region (500-240 nm) quantum yields are below 5 × 10^-6 electrons per incident photon. Below 240 nm the quantum yields rise sharply. The chls and chin exhibit similar yield curves; measured yields were of order 5 × 10^-6 electrons per incident photon at 240 nm, 1 × 10^-4 at 220 nm, and 1 × 10^-3 at 180 nm. These yields are at least 2 orders of magnitude greater than those of the amino acids and more than three orders of magnitude greater than that of phytol over this wavelength region. Photoemission observed in chl thin films is due to the porphyrin moiety of the molecule. High contrast is obtained in PE micrographs of chin deposited on substrates of bovine serum albumin, dipalmitoyl phosphatidylcholine, or starch. Chl is expected to be the dominant photoemissive component of thylakoid membranes and accounts for the image contrast observed previously in PE micrographs of spinach chloroplasts.     

The use of polarized bounded beams to determine the groove direction of a surface corrugation at normal incidence,the generation of surface waves and the insonification at Bragg-angles

Zero order reflected sound from a singly corrugated interface between a solid and a liquid, insonified from the solid side by circular polarized shear waves, can become almost perfect linearly polarized in a direction parallel or perpendicular to the corrugations, depending on the frequency, and can therefore reveal the direction of the corrugations. When narrow bounded beams, formed by a summation of infinite plane waves, are diffracted at certain frequencies, depending on the angle of incidence, or vice versa, one can predict phenomena like backscattering at Bragg-angle incidence and also the creation of Scholte-Stoneley waves.     

Speciation of alkyllead compounds by GC-AAS: A state of affairs

A synopsis of the organolead studies performed at our University is given. The different environmental applications such as air, wet atmospheric deposition and dust are summarized and the analytical characteristics of the extraction/derivatization/gas chromatography—atomic absorption spectrometry methodology for the species specific determination of ionic alkyllead species are described.     

Λ-Hypernucleus formation in proton-nucleus reactions

We study the production of hyperons inp + A reactions within the BUU transport approach including elastic N rescattering and extract the sticking probabilities and hypernucleus formation cross sections as a function of bombarding energy and target mass. At 1.5 GeV about 25% of the hyperons are found to be bound in case of heavy nuclei like²³⁸U leading to large cross sections for-hypernuclei. The respective hypernuclei show broad distributions in excitation energy, momentum and angular momentum. The decay of the hyperon in case of heavy targets is found to be almost entirely due to nonmesonic decay channels, i.e.N NN processes.Supported by BMFT, GSI, Forschungszentrum Jülich and the Polish Committee for Scientific Research under Grant no. PB2593/2/91     

The influence of the steric properties of the ligands PR2Ph and L on the formation and properties of the complexes Mo(η6-PhPR2)(L)(PPh2CH2CH2PPh2), R = Et,L = PPhEt2 and R = Ph,L = PPh3, PR′3, CO,CNR, N2, H2

The reduction of MoCl₄(DPPE) (DPPE = PPh₂CH₂CH₂PPh₂) with Mg or Na/Hg in the presence of 2 PPhR₂ under Ar results in the formation of the new complexes Mo(η⁶-PhPR₂)(PPhR₂)(DPPE) when R is Ph (Ia) or Et(II). No η⁶-PhPR₂ complex is obtained when R is Me because this small ligand forms strong MoP σ-bonds; nor is one obtained for R = Cy because of too much steric crowding. The limits for η⁶-complexation can be quantified in terms of cone angle sums.Complex Ia is very similar to Mo(η⁶-PhPMePh)(PMePh₂)₃ (IIIa) in that both react at similar rates with a variety of small ligands L = PMePh₂, PMe₂Ph, PMe₃, P(OMe)₃, N₂, CO, CNBu^t and H₂ via dissociation of a labile σ-bonded ligand. Several other less crowded η⁶-arylphosphinemolybdenum complexes including II do not have labile ligands at 25°C. The new complexes Mo(η⁶-PhPPh₂)(L)(DPPE) have been characterized by ³¹P and ¹H NMR, IR and gas uptake measurements, Ia has a higher affinity for H₂ than IIIa possibly because Mo(η⁶-PhPPh₂)(H)₂(DPPE) adopts a non-fluxional trans-configuration. The ³¹P chemical shift of the σ-bonded ligand in 8 derivatives of Ia and 12 of IIIa correlate with the sum of the cone angles of the three σ-bonded ligands in each complex.     

Untersuchungen in den Systemen: Hafnium—Bor—Kohlenstof und Zirkonium—Bor—Kohlenstofv

Zusammenfassung Die Dreistoffsysteme Hf–B–C und Zr–B–C werden an Hand heißgepreßter und lichtbogengeschmolzener Proben röntgenographisch untersucht. Da im Schnitt bei 1500 bzw. 1400° C keine ternären Phasen auftreten, werden beide Systeme von den Verbindungen der Randsysteme beherrscht. Im Hafnium-Bor-System wird ferner das Monoborid mit FeB-Struktur bestätigt, während im Zirkoniumsystem keine Anzeichen für ein analoges ZrB gefunden werden konnten. HfC_1–x vermag rund 6 At% B, ZrC_1–x nur wenig B aufzunehmen. Die Diboride lösen praktisch keinen Kohlenstoff, dagegen wird das Hafniummonoborid durch kleine Kohlenstoffgehalte stabilisiert. In abgeschreckten Schmelzlegierungen tritt es dagegen nicht auf; ebenso konnte ZrB₁₂ bei 1400° C und in ternären Schmelzproben nicht gefunden werden.Infolge der bestehenden Gleichgewichtsverhältnisse im System Zr–B–C(N) und Hf–B–N lassen sich Mischungen der betreffenden Diboride und Monocarbide (Mononitride) mit den Übergangsmetallen selbst abbinden. Im System Zr–B–C erhält man dabei verhältnismäßig zähe Hartmetalle.Mit 5 Abbildungen