RUTHERFORD BACKSCATTERING SPECTROMETRY: A LABORATORY DIDACTIC PATH ABOUT THE BASIC INTERPRETATION MODELS

Each time a new physical phenomenon is understood in depth, new techniques of analysis are produced, which employ the fresh knowledge to start new researches in unexplored field. Most of the techniques for material science are based on quantum mechanics, since matter is studied in terms of interactions with its microscopic components (e.g. atoms, nucleuses and electrons) or aggregates of them (e.g. molecules, crystals, phonons). However, due to the strong orientation of the techniques to gain qualitative or quantitative information (doing measurements), they are often interpreted according to semi-classical or classical models (e.g. the effective mass for conduction of a charged particle, the electron gas in a metal, the phonon as a harmonic oscillator etc.). In this sense, the analysis techniques can be introduced in physics education as a bridge between classical physics and quantum mechanics with its applications. Moreover, these techniques offer an opportunity to introduce stimulating topics of modern physics which in most cases constitute also a synthesis of various topics traditionally taught in separate contexts (mechanics, thermodynamics, electromagnetism etc).Rutheford Backscattering Spectrometry (RBS) is an analysis technique largely used in material science [1] and it constitutes a candidate technique for secondary school level students. It can be entirely understood and interpreted in terms of classical models and the teacher is free to deal with each concept also in terms of quantum mechanics. Moreover RBS can be an exciting subject for students since they can feel the experience, as in the research field, of interpreting a spectrum and obtaining structural and elemental information about an actual sample applying physical concepts and models.The didactic proposal that will be presented follows previous experience and research works about the introduction of the analysis techniques into the curriculum of secondary school [2-8] and benefits from a direct involvement in the use of RBS for condensed matter analyses. The aim of the activity is to enable students to deal with simple, not trivial RBS spectra and to discuss them in an appropriate scientific language. The materials were prepared for a course of the second level master in modern physics \u201cInnovazione Didattica in Fisica e Orientamento\u201d (Didactic Innovation in Physics and Orientation) for teacher training [9] and, subsequently, employed in various occasions of student involvement in modern physics and hands-on minds-on activities