LABORATORY FOR PHYSICAL CHEMISTRY II
Learning outcomes of the course unit
Application of some key-concepts in quantum mechanics.
Familiarization with some spectroscopic techniques (UV-vis-NIR-IR absorption, FT-IR, Raman).
Interpretation of spectroscopic data and their use for getting molecular parameters.
Knowledge of the basic concepts of Quantum Mechanics, of Physics and Mathematics.
Course contents summary
Particle-in-box model: application to organic dyes.
Introduction to Fourier transform. Michelson interferometer. FT-IR spectrophotometer. Roto-vibrational spectra of diatomic molecules.
Group theory: definition of a group, symmetry elements, symmetry groups, reducible and irreducible representations. Reduction of the representations. Connection to quantum mechanics.
Definition of the vibrational normal modes and their symmetry (with examples). Use of group theory for the evaluation of integrals of interest in quantum mechanics. Selection rules for IR spectroscopy. Raman spectroscopy and its selection rules. Prediction of IR and Raman activity for molecules of different symmetry.
Huckel method: approximations, resolution of the problem and calculation of atomic charges, bond orders, dipole moments. The 4n+2 rule; use of symmetry.
- Electronic spectra of organic dyes.
Recording of the vis-NIR absorption spectrum of organic dyes with increasing chain length. Interpretation of the results based on the particle-in-a-box model. Vibronic structure of the spectra.
- Roto-vibrational spectrum of HCl.
Recording of the IR absorption spectrum of an HCl gas sample with an FT-IF spectrophotometer.
Interpretation of roto-vibrational spectrum. Effects of the centrifugal distortion, anharmonicity, roto-vibrational coupling. Morse potential. Overtones.
Roto-vibrational structure of the fundamental transition: R and P branches. Isotopic effect. Effect of the spectral resolution and use of apodization techniques.
Exploitation of the experimental data to extract some molecular parameters.
- Infrared and Raman spectra of inorganic salts having anions of different symmetry.
Recording of the IR and Raman spectra of solid samples. Interpretation of the spectra via group theory.
- Calculation of the electronic structure of an unsaturated hydrocarbon via the Hückel method.
The exercise consists in the resolution of the pi electronic structure of an unsaturated hydrocarbon with the Hückel method. Determination of energies, bond orders, atomic charges, dipole moments. Determination of the symmetry of molecular orbitals and of ground and excited states though the application of group theory. Prediction of allowed and forbidden electronic transitions.
- P. W. Atkins, Molecular Quantum Mechanics, Oxford University Press.
- F. A. Cotton, Chemical Applications of Group Theory, Wiley 1990.
- D. P. Shoemaker, C. W. Garland, J. P. Nibler, Experiments in Physical Chemistry, McGraw-Hill 1996.
Classes, exercises and lab experiments.
Assessment methods and criteria
Learning is evaluated based on the participation to the exercises and lab experiments, of the reports and laboratory notes, and of the final oral examination.
The participation to the lab experiences is mandatory. Each student will have only one possibility to recover an eventually lost experiment.
At the end of the course, any student missing one or more lab experiment will not be allowed to final exam and will have to attend once again the Laboratory Course during the following year.
Each student has to keep a laboratory notebook, to be filled (with a pen) during each lab experiment, reporting the procedures and the data. This notebook has to be signed by the Professor at the end of each experiment.
Moreover, for each experiment, each student has to prepare a report, where to resume the experiment, the concepts at the basis of it, the results and conclusions. The ensemble of the reports must be delivered, together with copies of the laboratory notes, not later than the end of the following month of September. In case the reports are not delivered in due time, the student will not be admitted to the final exam and will have to attend the laboratory course once again during the following year.
The final oral examination (where you are admitted only if you followed each lab experiment and delivered the reports in due time) is carried out together with Physical Chemistry II.