Optical spectroscopy—typically covering the infrared, visible, and ultraviolet spectral ranges—is a powerful technique to study the properties of atoms, molecules, and materials. It generally relies on the absorption or (re-)emission of photons with characteristic frequencies that match the energy of quantum transitions in the investigated matter. Different transitions interact to a varying extent with electromagnetic radiation in accordance with the relevant selection rules. Typically, the selection rules describe the interaction of the electric field (EF) component with the molecular (transition) electric dipole (ED) moment, which is the leading term in light–matter interaction at optical wavelengths. Nevertheless, other terms like the magnetic field (MF)–magnetic dipole (MD) moment interaction also contribute on a smaller scale to absorption and emission, but usually they are masked by the far stronger ED interactions.
Since MD interactions follow different selection rules they can deliver unique extra information about molecular properties in optical spectroscopy. This provides an intriguing opportunity to establish a new form of direct “magneto-optical spectroscopy” complementary to traditional EF-based spectroscopy. Such a magnetooptical spectroscopy is still in an embryonic state, where only few pioneering works appeared so far.[1–3] Thus, within iStOMPS we want to bring experimental and numerical methods for magneto-optical spectroscopy to the next stage of maturity by joining the forces of three independent research teams in an interdisciplinary consortium. We aim at using state-of-the-art techniques from ultrafast laser technology, nonlinear optics, and structured materials to produce MFs oscillating at optical frequencies, spatially isolated from the concomitant EF component. This will allow the unperturbed detection of MF–MD interactions, giving access to this additional “magnetic sense”. Simultaneously, we will develop general computational means to predict and interpret MD spectroscopy using modern ab initio methods and simulations of electromagnetic fields.
The main tasks of iStOMPS are: (i) Development and optimization of experimental methods to effectively isolate oscillating MFs from EFs and irradiate samples exclusively with strong, transient MFs; (ii) Proof-ofprinciple experiments with different targets to measure their MD-only absorption or excitation spectra and the time-resolved relaxation dynamics after MD excitation; (iii) Development of a computational framework that can be used for the accurate and efficient ab initio prediction of MF-induced processes in matter.
