Modul M.Che.1311 (SoSe 2021, 6Cr)

Vibrational Spectroscopy and Intermolecular Dynamics

(Schwingungsspektroskopie und zwischenmolekulare Dynamik)

The lecture (3h/week, Tuesdays, 8:15-11:00 AM, formally MN28, but actually via Stud.IP/meetings, starting 13.04.21) is one among currently 5 choices for more specialized Physical Chemistry lectures in the Chemistry Master's program. In the summer term 2021 it will be held in English to allow for participation in the Master's program despite a possibly limited command of German. Active participation in the accompanying tutorial (tentatively Monday, 12:15-1:00 PM or 1:15-2:00 PM, discussing homework exercises) is urgently recommended, to optimize performance in the final written exam (180 min, planned for 13.07.21, 8AM and fall 2021). In addition, weekly voluntary multiple choice tests (Stud.IP) to check your level of understanding are offered. The next occasion to attend this lecture is planned for WiSe 2022/23 (then mostly in German). See Stud.IP for further information.

A brief meeting on organizational details will be offered on 13.04.21, 8:00 AM

Lecture program (incl. date):

Vibrating diatomics (13.04.)
Introduction into the lecture topic, molecular vibration, classical-quantum mechanical correspondence, harmonic oscillator, Morse oscillator, wavefunctions, energy levels, infrared spectrum, rotational constants, mechanical and electrical anharmonicity, matrix elements, overtone intensity
Molecular symmetry I (20.04.)
symmetry operation, symmetry element, symmetry group, group properties, point groups, symbols, proper rotation, reflection, inversion, improper rotation, abelian groups with at most two-fold axes, examples, subgroups, classification scheme, other symmetry groups and their classification
Molecular symmetry II (27.04.)
symmetry properties of molecular properties, characters, example C_2v, character table, irreducible representations, Mulliken symbols, coordinate systems, symmetrization, further abelian groups and their character tables, subgroups, symmetry number, chirality, dipole moments, transition dipole moments, harmonic oscillator
Molecular symmetry III (04.05.)
molecular vibrations exemplified for water, matrix representation of atomic displacements, trace, reducible representations and their reduction, translational, rotational and vibrational degrees of freedom, normal modes, symmetry reduction, selection rules, Raman, IR, C_3v, degenerate representations, molecular symmetry groups
Normal modes (11.05.)
Hamilton function, mass-weighted displacement coordinates, similarity transform, normal coordinates, degeneracy, stretching modes in CO₂, matrix notation, symmetric and antisymmetric stretching mode, kinematic coupling, valence force constants, functional group vibrations, fingerprint vibrations
Anharmonic effects (18.05.)
Anharmonicity constants in polyatomic molecules, Fermi resonance, coupling matrix elements, solution of the 2x2 problem, limiting cases, wavefunction character, example CO₂, vibrational terms, variational calculations, potential hypersurfaces and coordinate choice, state of the art, diffusion quantum Monte Carlo, concept, derivation based on the time-dependent Schrödinger equation, analogy to a transport equation, double minimum potential, tunneling splitting and period, ring puckering, torsion potential
Experimental techniques in vibrational spectroscopy (25.05.)
Application range, historical evolution, IR, Raman, neutron scattering, fluorescence, detectors, photovoltaic and thermal detectors, detector noise, cross section, Beer-Lambert law, light sources, thermal emitters, tunable lasers, optical materials, FTIR spectrometer
Intermolecular interactions (01.06.)
Electrostatic interactions, multipole expansion, dipole, quadrupole, potential energy, dipole-charge, dipole-dipole, thermal averaging, dipole-quadrupole, quadrupole-quadrupole, induction, polarisability, dispersion interactions
Structures of moleclar clusters (08.06.)
Pauli repulsion, supermolecule approach, anisotropy in the bonding region, Ar-HX examples, HX-HX examples, water dimer, quadrupolar molecules, structure determination methods, hydrogen bonds, energy and structure contributions, structure, relevance, directionality, oligomers, solid state structures, rings and cages, history
Potential energy hypersurfaces and vibrational dynamics of molecular clusters (15.06.)
Lennard-Jones potential, well depth estimates, van der Waals radii, mixing rules, Buckingham potential, partial charges, Stockmayer potential, empirical force fields for molecular mechanics and biochemistry, refined model potentials, pair approximation, three-body forces, induction, Pauli repulsion, Axilrod-Teller term, importance of many-body forces, zero-point vibration, He dimer, intermolecular vibrations, intramolecular vibrational shifts, the case of t-butyl alcohol, intensity enhancement, predissociation, Franck-Condon transitions, down shift and bond strengthening, OH band broadening in solution, tunneling splitting, energy flow after excitation
Experimental methods and examples for cluster generation and cluster spectroscopy (22.06.)
Aggregation, condensation, natural molecular clusters, aggregates in solution, matrix isolation, enclosive flow cooling, supersonic jet expansion, IR-spectroscopy, absorption spectroscopy, cavity ring-down spectroscopy, size selection by scattering, water clusters, carboxylic acid clusters, ionic clusters, clusters in clusters
Miscellaneous (29.06.+06.07.)
UV/IR techniques, fs-spectroscopy in solution, exciton coupling in water, anharmonic calculations, vibrational microscopy, molecular sociology, oscillator model of dispersion, chirality recognition, evaluation, good scientific practice
Exam (1st option, 13.07.21)
Exam (2nd option, 11.08.21)
previous examples

Modul M.Che.1311 (SoSe 2021, 6Cr)

Vibrational Spectroscopy and Intermolecular Dynamics

(Schwingungsspektroskopie und zwischenmolekulare Dynamik)

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