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A generalization of the Keldysh ionization amplitude derived previously which incorporates rescattering is used to calculate above-threshold ionization spectra for medium-high intensity (∼10 14 W cm −2 ). Quantum interferences are identified and shown to be capable of causing above-threshold ionization peaks to rise and fall by an order of magnitude when the laser intensity changes by only a few per cent. The calculations are carried out for a zero-range binding potential. Comparison with available three-dimensional accurate calculations for a Coulomb potential shows sufficient agreement suggesting that predictions based on the zero-range potential are qualitatively reliable. † Also at

SynopsisMagnesium aluminum alkyls containing higher (C,-C,,,) radicals were studied as components of Ziegler-Natta catalysts in styrene polymerization. The effects of alkyl radical length and MgR, contents in the components mentioned on the degree of TiCl, reduction and stereospecific activity of the catalysts were investigated. The components studied exhibited high reducing (for TiCl, ) and catalytic activities. Molecular weight of the synthesized isotactic polystyrene was abnormally high.