MT420  Quantum Theory II  (given in 2007-8)

Prerequisite:   MT320

Teaching:        33hr lectures

Assessment:   2hr written examination

Aims

·        To derive methods, such as the Rayleigh-Ritz variational principle and perturbation theory, in order to obtain approximate solutions of the Schrödinger equation.

·        To introduce spin and the Pauli exclusion principle and hence explain the mathematical basis of the Periodic table of elements.

·        To introduce the quantum theory of the interaction of electromagnetic radiation with matter using time dependent perturbation theory.

·        To show how scattering theory is used to probe interactions between particles and hence to show how the probability or cross section for a scattering event to occur can be derived from quantum theory.

Learning outcomes

On completion of the course students should be able to:

·        use various methods to obtain approximate eigenvalues and eigenfunctions of any given Schrödinger equation,

·        to understand the importance of spin in quantum theory,

·        to appreciate how the Periodic Table of elements follows from quantum theory,

·        to write down the Schrödinger equation for the interaction of electromagnetic radiation with the hydrogen atom and to work out photoabsorption cross sections for hydrogen,

·        to define the scattering cross section and to work it out for some simple systems.

Content

Variational principles in quantum mechanics:  the Rayleigh-Ritz variational principle.  Bounds on energy levels for quantum systems.

Perturbation theory:  Rayleigh-Schrödinger time-independent perturbation theory.  Perturbations of energy levels due to external electromagnetic fields.

The electron’s spin:  the eigenfunctions and eigenvalues of the spin operator.  The Pauli exclusion principle.  The periodic table of elements.  Spin precession in an external magnetic field.

Radiative transitions:  the absorption and emission of electromagnetic radiation by matter. Photoabsorption cross-sections for the hydrogen atom.

Scattering theory:  definition of the scattering cross-section and the scattering amplitude.  Decomposition of the scattering amplitude into partial waves.  Phase shifts and the S-matrix.  Integral representations of the scattering amplitude.  The Born approximation.  Potential scattering.

Indicative texts

Quantum Physics – S Gasiorowicz  (Wiley 1974)  Library reference 530.12 GAS

Quantum Mechanics – P C W Davies  (Chapman and Hall 1984)

Library reference 530.12 DAV