Modification of the surface state and doping of CdTe and CdZnTe crystals by pulsed laser irradiation

The photoelectric and electrical properties of high-resistivity p-like CdTe and Cd_0.96Zn_0.04Te single crystals and barrier structures on their base before and after laser irradiation in different conditions are studied. Irradiation of samples with nanosecond ruby laser pulses was carried out in two different ways. In the first case, the Cd(Zn)Te crystals were subjected to laser action directly from the surface and irradiation within a certain range of intensities resulted in a decrease in the surface recombination rate and increase in the photoconductivity signal. The surface region with a wider bandgap in CdZnTe crystals was formed. In the second case, the samples were irradiated from the side pre-coated with a relatively thick In dopant film and it caused rectification in the I-V characteristics as a result of laser-induced doping of the thin Cd(Zn)Te surface region and formation of a built-in p-n junction. The application of the fabricated M-p-n structured In/Cd(Zn)Te/Au diodes for X-ray and γ-ray detectors is discussed.     

Reverse-docking study of the organocatalyzed asymmetric Strecker hydrocyanation of aldimines and ketimines

A methodology for reverse-docking flexible organocatalysts to rigid transition state models of catalyst-free asymmetric reactions has been developed. The investigation of Jacobsen's chiral thiourea-based organocatalyst for the hydrocyanation of aldimines and ketimines (Strecker reaction) via reverse-docking is described. Results from reverse-docking Jacobsen's organocatalyst to both enantiomers of six Strecker TS-models (i.e., rigid transition state models of the catalyst-free asymmetric reaction) indicate a clear energetic preference for binding the organocatalyst to the R-enantiomer TS-model, which is in agreement with experimental results. The most favorable docking poses reveal structural features consistent with principles of molecular recognition, catalysis, and NMR data. These poses may represent simplified geometric models of the transition state for the catalyzed reaction.     

Time dependent contributions to the effective order of non-linearity for two photon ionization

The typical definition of the effective order of non-linearity, k = ?_lnIlnN_ion is found to be time dependent for high light intensities. An alternative definition is presented for comparison of theoretical and experimental quantities.