Positron annihilation lifetime studies of changes in free volume on some biorelevant nitrogen heterocyclic compounds and their S-glycosylation

A series of N-heterocyclic compounds was investigated by positron annihilation lifetime spectroscopy as well as Doppler broadening of annihilation radiation (DBAR) at room temperature. The results showed that the formation probability and life time of ortho-positronium in this series are structure and electron-donation character dependent, and can give more information about the structure. The DBAR provides direct information about the change of core and valance electrons as well as the number of defect types present in these compounds.

Simulations of Gamma Cascades and Modelling Atomic Collision Chains

A new method for simulation of nuclear γ cascades by the Monte Carlo technique is described. It makes it possible to generate artificially individual events of the γ-cascade decay of neutron capturing states in heavy nuclei. For the purpose of determination of lifetimes of nuclear levels by the GRID method the previously developed Mean Free Path Approach for modelling atomic collisions and their interplay with cascades has been generalized. Examples of the use of this generalization for determination of lifetimes of selected (150)Sm and (158)Gd levels are given and discussed.