Heavy ion irradiation effects: Dettecting metallic colloids in calcium fluoride crystals by optical absortion and fluorescence

• Grant number: 22/14906-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: February 01, 2023
• End date: November 30, 2023
• Field of knowledge: Physical Sciences and Mathematics - Physics - Condensed Matter Physics
• Principal Investigator: Igor Alencar Vellame
• Grantee: Maurício Maekawa Chaves
• Host Institution: Instituto de Física Gleb Wataghin (IFGW). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil

Abstract

Investigating the radiation interaction with matter allows one to verify predictions based on theoretical modelling as well as to develop various applications, including those present in research areas such as nuclear medicine and nanotechnology. When matter is in the solid state, the ionizing radiation is able to transfer its energy to the target causing structural modifications. However, the mechanisms responsible for the conversion of the transferred energy to these structural modifications are still on debate in the literature and only a robust experimental database would furnish the means to unsolve the most efficient mechanisms for materials with different physical and chemical properties. In this research project, we intend to experimentally address the formation of point and extended defects in calcium fluorite crystals irradiaded with heavy ions in the non-relativistic, electronic regime. Data analysis will focus on the use of optical absorption and fluorescence microscopy techniques for crystals irradiated with different ion fluences. Due to the extremily large band gap, point defects are able to trap electrons and holes. These centers absorb electromagnetic radition in the visible spectrum and fluoresce, providing information concerning the kind of defect, its concentration and its spatial distribution. Due to the partial radiolysis of the crystals when exposed to radiation, extended defects are associated to metallic colloids and gaseous inclusions. The colloids scatter electromagnetic radiation and induce surface enhanced Raman scattering, providing information concerning their size distribution and the violation of the selection rules for phonon detection. Based on the analysis, we aim to understand why such crystals are particularly efficient in forming metallic colloids.