Ab initio calculations of the photoionization of diatomic molecules

A review is presented of the calculation of photoionization spectra, particularly in the spectral range where electron autoionization of diatomic molecules takes place. In addition to some interesting results obtained over years that compare favourably with experiment, the emphasis here is put on the relation between the methods developed for the calculation of observables associated with the continuum energy spectrum of the electrons and the Alchemy system of programs. This system of programs serves as a basis for initial and intermediate calculations. The examples presented show that diatomic molecules not only in gas phase but also oriented in space or physisorbed at surfaces may be studied readily.     

An improved synthesis of (-)-7-isopropyl-cis-l-amino-2-indanol the chiral auxiliary for 6π-azaelectrocyclization

(-)-7-Isopropyl-cis-1-amino-2-indanol,a key chiral auxiliary and ligand in the highly stereo-selective asymmetric 6π-azaelectrocyclization, has been prepared previously by two methods.Each however involved using of one extreme condition, i.e.high temperature or high pressure,for the respective reaction.A modified reaction route employed mild condition for synthesis was presented in this report.     

An introduction to balanced sequential arrays on the square grid

Plants grown in large numbers for commercial purposes are usually set out on a regular grid, triangular, square or hexagonal, or possibly a rectangular grid. We need to understand their behaviour when they compete with each other for light, water and nutrients. In a greenhouse, there may be a lamp over each plant, half the plants having their lamps on and half off. The intensity of light falling on any particular plant is determined mainly by whether its own lamp is on, next by the number of its nearest neighbours whose lamps are on, and perhaps also by the number of its second-nearest neighbours whose lamps are on. Such arrays are also used to study competition among different types of plants and, with some extra restrictions, to design field layouts as well. The problem of constructing suitable arrays was introduced in [CORMACK, R. M.: Spatial aspects of competition beween individuals. In: Spatial and Temporal Analysis in Ecology (R. M. Cormack and J. K. Ord, eds.), International Co-operative Publishing House, Fairland, Maryland, USA, 1979] and discussed in [GATES, D. J.: Competition between two types of plants with specified neighbour configurations, Math. Biosci. 48 (1980), 195–209]. Here we consider only the square grid. To Alex Rosa, on the occasion of his seventieth birthday     

A.C. susceptibility and magnetisation measurements on polysulphur nitride, (SN)x

Measurements of the complex A.C. susceptibility and magnetization of crystals of polysulphur nitride, (SN)_x, are reported. At temperatures near 0.2K both the in-phase and quadrature components of the A.C. susceptibility show a marked change which can be related to the onset of superconductivity. However, changes in the sample magnetization could not be detected.     

Novel rearragements of 7-oxanorbornene systems

Treatment of the tricyclic 7-oxanorbornene systems with electrophiles (I⁺, Br⁺) leads to skeletal rearrangement.     

Time-resolved luminescence in amorphous semiconductors

Time-resolved luminescence spectra of some amorphous semiconductors are reported. In a-Si:O:H, the Coulomb interaction of the recombining electron and hole is explicitly observed in the time dependence of the luminescence peak position, at delay times ranging from 200 nsec to 30 μsec. Peak shifts at longer times are analyzed in terms of a distribution of recombination energy due to band tailing. It is deduced that the addition of oxygen to a-Si:H broadens the tails. In As₂S₃ we find no evidence of the Coulomb interaction, and this result supports the charged defect model.     

Electrical properties of (SN)x films

The temperature dependence of the thermopower S and the conductivity σ of (SN)_x films has been investigated as a function of the substrate temperature during film deposition T_s. In contrast to the transport properties of SN_x films previously reported, films made with high T_s have metallic-like transport properties approaching those of (SN)_x crystals. For low substrate temperatures σ and S are found to increase strongly with rising temperature and thermopower values up to 0.9 mV/K are observed. This conduction behavior is explained by a heterogeneous model with areas having different electronic gaps. Annealing as well as decomposition effects suggest that the gap width is correlated to the (SN)_x chain length. No evidence was seen for superconductivity in these films.