Recent developments in energy, time and spatial resolution at large scale experimental facilities are increasing the demands on theory and simulation support. This increasing need for support in interpreting, as well as designing, experiment is driving demand for more precise and more accurate theory and simulations than ever before. In an attempt to meet these needs, the proposed Spectroscopy Masterclass will teach the use of state-of-the art computational methods to experimentalists at the UK's large large scale facilities and their user communities and connect these to the academic community of researchers in condensed matter theory.

By hosting the event at the location of the Diamond synchrotron, the Central Laser Facility and ISIS neutron and muon source, which are co-located at Rutherford Appleton Laboratory, UK, the event will emphasise the synergy between theory and experiment and place it at the heart of its target community; this motivated us to take the step of including leading scientists from the three large scale facilities as advisory co-organisers for the event.

This masterclass will teach powerful methods for different spectroscopies and enable researchers in spectroscopy to understand the ranges of applicability of the different theoretical methods, to choose the most appropriate code for a specific spectroscopy problem and to perform tutorial calculations for those that can be later adapted to their research questions. Participants will be be brought up to date with the state of the art and given a broad overview of the different methods available, with specific examples given which illustrate the use of the codes and their common pitfalls and other considerations. 

The specific theories that will be covered are: core-level spectroscopies (typically x-ray) described by multiple-scattering techniques (code: MsSpec[1]), low energy electronic band structures described using the KKR Green's function formalism, including effects of strong electronic correlations and with an explicit treatment of the photoelectron emission process (code: SPR-KKR[2][3]) as well as high-accuracy calculations with many-body perturbation theory (GW and beyond; code: Questaal[4][5]). Each of these codes may be considered state-of-the-art in their respective application areas. The taught theoretical spectroscopy methods will have application beyond any specific individual experiments, within the broad remit of x-ray, photo-electron and electron energy loss experiments, for both ground-state and nonequilibrium properties as well as magnetism.  Recognising that experimentalists typically have rather focused interests, a series of break-out sessions teaching on specific topics will be delivered in parallel.

Bringing beam-line scientists, their collaborators and the theoretical spectroscopy community together allows experimentalists to feedback to the theory community, identifying areas requiring attention by theorists. Ample time is allocated for discussion and interactive engagement by the participants, who will be expected to present posters and describe them with short "pico" talks. Fostering new collaborations between theory and experiment, both nationally and internationally, will be a main focus of the school. The event will feature three codes, each of which are collaborative software projects with users and developers across Europe and beyond. The event will welcome international participants both as students and speakers.