79466 - Spectroscopy of Condensed Phases

Learning outcomes

Modern research in chemistry and materials science involves the interaction of radiation with condensed-phase systems such as molecules in liquids and solids as well as aggregates, metals, semiconductors, and composites. The course aims to provide the student with a basic description of a number of spectroscopic phenomena associated with such systems, with elementary treatments of fundamental theoretical concepts. Starting from the basics of traditional molecular spectroscopy, optical processes will be treated with emphasis on the condensed phase perspective, to include metals, glasses and molecular crystals. Experimental techniques will be addressed with the goal of understanding spectroscopic data

Course contents

Solid-State Concepts for Molecular and Organic Materials

1. Classification of the States of Matter.
   Overview of solid, liquid, gas, and mesophases. Focus on the solid crystalline state. Introduction to amorphous vs crystalline solids, with emphasis on molecular crystals relevant to organic electronics.

2. The Solid Crystal State.
   Intermolecular interactions and binding in crystals, including van der Waals, hydrogen bonding, and π–π interactions in organic molecular crystals. Crystal structure and unit cells; Bravais lattices. Crystal symmetry: structural view, mathematical representation, and reciprocal lattice. Introduction to Bloch functions in the context of periodic molecular solids.

3. Electronic Structure of Molecular Solids.
   Simplified treatment of the electronic structure of molecular crystals. Energy band formation in organic molecular solids: model systems and band diagrams. Density of states (DOS) in the context of disordered and crystalline organic materials.

4. Excited States and Excitons in Molecular Aggregates.
   Excited states in aggregates of organic molecules: Davydov splitting, mini-excitons, and exciton delocalization in linear molecular crystals. Frenkel excitons: formation, transport, and coupling with vibrations. Physical dimers and excimers in molecular crystals. Band structure of excitons in organic semiconductors.
   Charge transfer excitons (CT); exciton dissociation and binding energy.
   Exciton processes in organic optoelectronic devices: exciton diffusion, energy transfer mechanisms, exciton-exciton and exciton-polaron interactions. Role of excitons in organic photovoltaics (PV), light-emitting diodes (OLEDs), and field-effect transistors (OFETs).

5. Vibrations in Solids.
   Classical lattice dynamics: vibrations of one-dimensional monatomic and biatomic chains; dispersion relations; acoustic and optical branches. Extension to three-dimensional crystals. Vibrational properties of molecular crystals and the quantization of vibrational energy. Introduction to phonons and their interpretation as quasiparticles. Discussion focused on organic molecular crystals and their low-frequency dynamics.

6. Scattering and Vibrational Spectroscopy.
   Interaction of phonons with light and matter: phonon-photon scattering (Raman, IR), and elastic/inelastic processes.

Readings/Bibliography

All lecture notes and supplementary teaching materials will be provided through the Virtuale platform throughout the course.

Useful readings:

• Electronic Processes in Organic Semiconductors: An Introduction, Anna Köhler and Heinz Bässler, ISBN: 9783527332922, 2015, Wiley‐VCH Verlag GmbH & Co. KGaA.

• Organic Molecular Solids, Markus Schwoerer and Hans Christoph Wolf, ISBN: 9783527405404 | Online ISBN: 9783527618651 | DOI: 10.1002/9783527618651, 2005, Wiley‐VCH Verlag GmbH & Co. KGaA.

• Condensed‐Phase Molecular Spectroscopy and Photophysics, Anne Myers Kelley, ISBN: 9780470946701 | DOI: 10.1002/9781118493052, 2013, John Wiley & Sons, Inc.

Teaching methods

Lectures are delivered in person with the support of projected PowerPoint slides and other multimedia materials.

Opportunities for discussion and questions are encouraged throughout the lectures.

Assessment methods

The exam involves the presentation of a research article chosen by the student (or assigned by the instructor), focusing on subjects discussed during the course. The presentation is followed by a critical discussion and questions from the examiner.

 

Students with learning disorders and\or temporary or permanent disabilities: please, contact the office responsible (https://site.unibo.it/studenti-con-disabilita-e-dsa/en/for-students ) as soon as possible so that they can propose acceptable adjustments. The request for adaptation must be submitted in advance (15 days before the exam date) to the lecturer, who will assess the appropriateness of the adjustments, taking into account the teaching objectives.

Teaching tools

PowerPoint presentations, multimedia content (videos, animations), the recommended readings, lecture notes made available to students, and supplementary material provided via the Virtuale platform.

Office hours

See the website of Elisabetta Venuti