Reaction of trimethylaluminum and trimethylgallium with bifunctional amines: Syntheses and molecular structures of [Me2Al−N(CH2CH2)2−C−(OCH2)2]2 and [Me2Ga−N(Si(H)Me2)2]2

The crystalline products [Me₂Al–N(CH₂CH₂)₂–C–(OCH₂)₂]₂ (I) and [Me₂Ga–N(Si(H)Me₂)₂]₂ (II) were prepared from reactions of trimethylaluminum and trimethylgallium with 1,4-dioxa-8-azaspiro[4.5]-decane and 1,1,3,3-tetramethyldisilazane, respectively, in toluene. The organoaluminum dimer crystallizes in the monoclinic space groupP2₁/c with unit cell parametersa=8.970(2) ,b=9.683(2) ,c=12.833(3) , =103.18(2)°,V=1085.3(3) ³, andD _calcd=1.22 g cm^–3 forZ=2. Least-squares refinement based on 935 observed reflectionsI>3(I) in the range 3.5°<2<45.0° led to a finalR factor of 0.033 (R _w =0.041). The dimeric organosilazagallium crystallizes in the triclinic space group with unit cell parametersa=7.636(2) ,b=9.168(2) ,c=9.466(3), =72.81(2)°, =87.94(2)°, =69.90(2)°,V=593.0(3) ³, andD _calcd=1.30 g cm^–3 forZ=1. Least-squares refinement based on 1661 observed reflectionsI>3(I) in the range 3.5°<2<48.0° led to a finalR factor of 0.055 (R _w =0.070). Both compoundsI andII reside about a crystallographic center of symmetry and contain a planar M₂N₂ (M=Al forI, Ga forII) four-membered ring withI having an Al...Al contact of 2.801 .     

Determination of thorium in the range of low concentrations

Summary Methods for the determination of Th in the range of low concentrations are compiled and discussed. Application of spectrophotometry and voltammetry is investigated. Spectrophotometry is applicable down to concentrations of the order of 0.1 g/l as long as the ratio U:Th is low. Voltammetric determination of Th is not possible in the presence of Al.     

Analysis of experiments on energetic ions from laser produced plasmas with reference to hot electrons and pulsation

The need for highly charged heavy ions from projected particle accelerators has recently led to a re-evaluation of the complex processes of ion production in laser generated plasmas. Possible mechanisms for the production of intense beams of high charge state ions are investigated as is the experimental evidence for these mechanisms. The hypothesis that 20 keV ions are driven by hot electrons is not supported by experimental work to date. This work, on the other hand, suggests that 30ps pulsation is the basic mechanism for the acceleration of tantalum ions up to charge state 8+ whose energy increases linearly with charge state up to 24keV. For long pulses and charge states between 8+ and 18+, it appears that there is a secondary mechanism of electron impact ionisation by plasma electrons of approximately 200 eV in the plasma in front of the target, resulting in ions whose energy of around 24 keV is independent of charge state.