Positron Annihilation Spectroscopy

Using nuclear tools and techniques, the structure and dynamics of crystals, composites, nano-materials and soft condensed matter systems are probed. Positron annihilation spectroscopic techniques are employed to carry out studies on optical spectroscopy and photo chemistry of uranium in solution and liquid microemulsion system, studying the aggregation behaviour of the extractant, micelles/ reversed micelles, polymers etc. These studies are corroborated with complementary techniques such as light scattering, and photochemical methods. Study of positronium (Ps) pick-off annihilation in molecular substance including liquid systems, development of theoretical models, study of electron transfer reaction of Ps and spin conversion (electron spin exchange through paramagnetic ions) using inorganic solute ions in aqueous systems, and development of corresponding theoretical models are also carried out. Investigations of polymeric systems, multi porus materials, conducting polymers, radiation damage of polymers have also been done in the laboratory and the results are compared with gas absorption BET method. Study of some biologically important molecules, probing the biological importance of positron annihilation in medical diagnosis and usage of positron annihilation as a tool for surface studies have also been successfully conducted by the group. Positron annihilation spectroscopy was used for the studies of properties and processes related to defects in nano-materials including metals, alloys, ferrites and semiconductors. An interesting aspect of these studies has been to look for the effect of doping by other substitutional elements in a nanocrystalline system. Irradiation induced structural changes in metals, alloys and superconducting materials have been explored using the ion beams from the tandem Pelletron facility at TIFR, Mumbai and from the cyclotron at the Variable Energy Cyclotron Centre (VECC), Kolkata.

Link to Laboratory