Speaker
Description
Since decades the neutron and, more recently, Xray spectroscopies have been standard workhorses for investigations of condensed matter dynamics at atomic resolution. Nevertheless, the inherently weak interaction of both probes with matter, accompanied by the tiny flux densities of neutron beams and by the huge Xray photon energy as compared to the energy scale of elementary excitations in condensed matter, have restricted their implementation to studies of systems in thermodynamic equilibrium.
Experiments using synchronized pulsed Xray and laser beams to investigate the time evolution of non-equilibrium states of condensed matter, both in the structural and in the magnetic domains, have quickly become routine at XFEL (Xray Free Electron Lasers) beams exhibiting picosecond time-structures, accompanied by extreme transversal coherence (e.g. [1]). With neutrons the progress in source brilliance is extremely limited and the slow propagation speed is prohibitive for beam time-structures below the microsecond scale, but some compensation comes from the ease of energy transfer analysis. Recently, reports on successful attempts of time-resolved neutron work have appeared [2], demonstrating a very acceptable efficiency when applied to molecular processes on the micro- and millisecond scales [3,4].
In this lecture we shall recall the basic principles of scattering theory based on time-dependent correlation functions and review the present state of neutron experimental techniques addressing transient processes in matter, their principal limitations and emerging opportunities at newly built instruments [5].
References
[1] M. Trigo et al., Nat. Phys. 9, 790 (2013); doi: 10.1038/nphys2788
[2] C. Hua, D. A. Tennant, A. T. Savici, V. Sedov, G. Sala, and B. Winn, Rev. Sci. Instrum. 95, 033902 (2024); doi: 10.1063/5.0181310
[3] T. R. Reeder et al., PNAS 122, 2415300121 (2025); doi: 10.1073/pnas.2415300121
[4] T. Burankova, T. Hauß, J. Ollivier, R. E. Lechner, N. A. Dencher and J. Pieper, Biophys. J. 125, (2026) accepted for publication; doi: 10.1016/j.bpj.2026.02.028
[5] R. Toft-Petersen et al., Rev. Sci. Instrum. 96, 0258847 (2025); doi: 10.1063/5.0258847
