Johannes Viehmann

Highly charged cations are omnipresent species after the interaction of high-energy or high-intensity light with matter. When embedded in environments, the mechanism and outcome of the redistribution of the cation’s charge are crucial for the further fate of the whole system. Generally, ground-state cations can decay by charge transfer, proceeding radiatively, through nuclear dynamics, or by electron-transfer-mediated decay (ETMD). ETMD causes electron emission from a remote neighbor and appears ubiquitous in loosely bound systems. It remained unclear how multiply charged ions decay if conventional ETMD channels are closed. Here, we show that a yet undiscovered variant of ETMD is possible, where multiple electrons are collectively transferred. Explicitly, we observe ETMD in which two electrons from two distinct neighbors (partially) neutralize a multiply charged ion, and an electron from a fourth site is emitted. According to the established nomenclature, we suggest naming the process ETMD(4).

The two-dimensional photon-excitation photon-emission (PhexPhem) map of the archetypal H 2 molecule, constructed from dispersed-fluorescence measurements after energy-scanning excitation by small-bandwidth photons, displays complete systems of its Condon diffraction bands. They originate from spontaneous radiative dissociation of individual bound electronically excited rovibronic levels, one of the most relevant processes for the destruction of H 2 in space. For the B − X system of electronic states, we show that specific measured spectral characteristics of individual bands are extremely sensitive to the difference Δ R of the internuclear distances, where the two potential energy curves each have their minimum. Using data from recorded H 2 -PhexPhem maps, it is possible to experimentally validate the calculations of Δ R down to an accuracy of at least 50 f m . This accuracy may be used as a sensitive experimental test to calculational accuracy. It is well feasible to improve the currently achieved experimental accuracy, for an even more accurate benchmark of advanced potential energy curve calculations.