Peeling graphite layer by layer reveals the charge exchange dynamics of ions inside a solid

Abstract

Over seventy years ago, Niels Bohr described how the charge state of an atomic ion moving through a solid changes dynamically as a result of electron capture and loss processes, eventually resulting in an equilibrium charge state. Although obvious, this process has so far eluded direct experimental observation. By peeling a solid, such as graphite, layer by layer, and studying the transmission of highly charged ions through single-, bi- and trilayer graphene, we can now observe dynamical changes in ion charge states with monolayer precision. In addition we present a first-principles approach based on the virtual photon model for interparticle energy transfer to corroborate our findings. Our model that uses a Gaussian shaped dynamic polarisability rather than a spatial delta function is a major step in providing a self-consistent description for interparticle de-excitation processes at the limit of small separations.

Angle-dependent charge exchange and energy loss of slow highly charged ions in freestanding graphene

“…Additionally, the peaks shift to lower analyzer voltages, which points to increasing energy loss at higher scattering angles. The mean outgoing charge state is about 5, which is well in agreement with what was observed previously [13,30] for HCI transmission through graphene. To evaluate the data from Fig.…”

“…Further, at larger kinetic energies the ion approaches the target nuclei closer, i.e., for a given impact parameter p the closest approach R min is smaller but also the total transmission time is smaller. Interatomic energy exchange leading to the stabilization of resonantly captured electrons by ICD shows a saturation of the ICD rate at interatomic separations about smaller than the lattice constant of graphene (1.4 Å) [25,30]. Thus, we do not assume the ICD rate to be dependent on the closest approach, but rather that at larger kinetic energies the time the ion spends in the ICD active region around a target atom is too small for ICD to fully de-excite the ion.…”

Electron Spin Catalysis with Graphene Belts

“…In aerobic ORR catalysis, there are three electron transfer steps for the oxygen activation process: (i) electrons transferring from the cathode to the catalyst attached to the cathode surface ( Step 1 ); (ii) electrons transferring from the catalyst surface to vacancy defects ( Step 2 ); (iii) electrons transferring to the O 2 during physisorption, which leads to oxygen activation (Figure 3a). The first two processes take place on the femtosecond (fs) timescale, [30, 31] while the lifetime of OOH ads is 600 fs [32] . Therefore, the rate‐determining step for aerobic catalytic ORR is the third step, which involves the formation of a superoxide radical anion (O 2 +e − →O 2 .− ) [33, 34] .…”

Doublon Production in Correlated Materials by Multiple Ion Impacts

“…Such processes have recently become accessible to accurate measurements for highly charged projectiles impacting graphene and other correlated 2D materials (see, for example, Refs. [76,77]) and are still lacking a full theoretical description. The present NEGF approach within the G1-G2 scheme provides the proper starting point for this problem as it allows one to resolve the full dynamics of electronic correlations.…”