Advanced Spectroscopy

Course goals

Content

The investigation of materials has become one of the most dynamic and interdisciplinary fields in contemporary science, owing to their potential to lead to a dazzling multitude of applications (e.g., catalysis, solar energy conversion, optoelectronics, photonics, spintronics, biomedical diagnostic tools, etc.). Materials enable us to exploit hierarchically organized multiscale phenomena, through which events taking place at different time- and size-scales can be cooperatively coupled to produce an otherwise unachievable outcome. Examples of such multiscale processes can be found in many applications: chemical conversion in a catalyst, light to electricity conversion in a solar cell, electricity to light conversion in an LED display, light-driven chemical conversion through photosynthesis or photocatalysis, etc. All these processes result from coupled chain of events taking place at time scales ranging from fs to ms and length scales ranging from atomic to the macroscale, through the molecular, nano- and mesoscales. Spectroscopic techniques provide powerful tools to investigate materials at all the time- and size-scales that are relevant to understand and control multiscale processes.
The course will provide a deepened understanding of the fundamentals of the theory of spectroscopy and of the fundamental principles of various spectroscopic techniques. Aim of the course is to provide students with the knowledge and skills to quickly understand the working principles of spectroscopic techniques they later will use to characterize (nano)materials. The content taught will also enable them to choose the techniques that are best suited to elucidate a particular problem in Nanomaterials Science and to interpret the acquired data. The course consists of three parts, which are concisely described below.
The first part is taught by Matteo Monai and consists of five lectures, in which, after a brief introduction to the course, the quantum mechanical foundations of spectroscopy will be recapitulated and addressed. Subsequently, experimental methods and advanced data analysis in spectroscopy will be discussed. More specifically, the following topics will be addressed:
1. Quantum Mechanics and interaction of electromagnetic radiation with matter.
2. Atomic structure and atomic spectra, term symbols, selection rules
3. Experimental spectroscopic techniques
4. Advanced data analysis in spectroscopy

In the second part of the course, Celso de Mello Donegá will further develop the quantum mechanical background provided in the first part of the course (in particular: quantization, energy levels, light-matter interaction, term symbols, selection rules) to explain the fundamentals of electronic spectroscopy in the UV-Visible-Near-IR region, which involves the outermost electrons of atoms in ions, molecules and materials in general. To this end, first the fundamentals of electronic spectroscopy will be qualitatively addressed. Subsequently, the crucial impact of symmetry on the characteristics of electronic spectra (number of lines and intensities) will be discussed and treated in a semi-quantitative way by using group theory. More specifically, the following topics will be addressed in the second part of the course (5 lectures):
1. Fundamentals of electronic spectroscopy (qualitative): types of transitions, transition intensities and selection rules, term symbols, energy level splitting
2. Symmetry and group theory
3. Electronic spectroscopy (UV-Vis-NIR) and Symmetry: number and intensity of spectral bands, excited state lifetimes
4. Electronic spectroscopy (UV-Vis-NIR): transition linewidths (homogeneous and heterogeneous), Frank-Condon principle, configurational coordinate model, fates of electronically excited states

In the third part of the course, which consists of 5 lectures, Frank de Groot will address electronic spectroscopy in the X-rays region, which involves core electrons. The concepts discussed in the previous two parts of the course will be required as background (quantization, energy levels, light-matter interaction, term symbols, selection rules, symmetry and group theory). An overview of x-ray spectroscopies will be given including x-ray absorption, x-ray emission, x-ray photoemission, Auger spectroscopy and resonant inelastic x-ray scattering. X-ray spectroscopy simulation software will be used during the course and exercises. This software will also be used to generate Tanabe-Sugano diagrams, i.e. the energy positions of multi-electron states as visible in UV-vis and x-ray spectroscopies.