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Quantum-chemically supported electric beam deflection and photodissociation spectroscopy reveal the shape evolution and optical absorption of small Sn clusters with focus on the rotational, vibrational, multiphoton and dissociation characteristics.

A combined experimental and quantum‐chemical study of the structure and optoelectronic properties of isolated non‐stoichiometric CdxSey + clusters with x=3, 4 and y=3, 4 is presented. The consistency of optical response calculations with the measured absorption spectra reveals that the theoretically predicted lowest energy structural isomers have been formed in the molecular beam experiments. The Se‐rich nanocluster Cd3Se4 + contains a Se2 − unit which is responsible for the enhanced light absorption in the visible spectral range. In contrast, the radical electron of the Cd‐rich species Cd4Se3 + is localized at a Cd+ centre which is attached to a six‐membered Cd3Se3 ring. The excess Cd atom is partly responsible for an intense optical absorption in the near ultraviolet. The variation of the geometry and the optical behaviour in dependence of the stoichiometry is discussed with respect to the photocatalytic properties of CdSe nanoparticles, The manipulation of the stoichiometry of isolated cationic CdSe nanoclusters is experimentally and theoretically examined. Especially its effect on the geometry, optical properties, chemical bonding, electronic structure and on photocatalytic activity is discussed. It is demonstrated, that the localization of the unpaired electron on different atomic centres in dependence of the cluster composition highly affects the aforementioned properties.

The synthesis of atomically precise clusters is nowadays well established. The study of isolated clusters in the gas phase has also become an approved field of research. Although both approaches ex...

The global optimization of nanoparticles, such as pure or bimetallic metal clusters, has become a very important and sophisticated research field in modern nanoscience. The possibility of using more rigorous quantum chemical first principle methods during the global optimization has been facilitated by the development of more powerful computer hardware as well as more efficient algorithms. In this review, recent advances in first principle global optimization methods are described, with the main focus on genetic algorithms coupled with density functional theory for optimizing sub-nanometre metal clusters and nanoalloys.

In the present work, the optical response of isolated (CdSe)n+ clusters with n = 3–6 is probed by measuring the photodissociation cross section in the photon energy range ℏω = 1.9–4.9 eV. In this j...

Photoabsorption spectra of isolated Si6–100+ clusters are presented in the energy range of ℏω = 1.9–5.4 eV. By measuring the absolute photodissociation cross sections, this work attempts to bridge ...

Recently synthetic aperture radar (SAR) has become implemented in multi-receiver systems to achieve, for example, along track interferometry (ATI) and/or digital beam forming (DBF) for wide observation swath. In this paper, we propose a novel radio frequency interference (RFI) detection method especially for multi-receiver SAR systems. We assume that RFI signals have greater similarity than the summation of radar echoes among multiple receivers. Based on this idea, we performed an interferometric analysis of the SAR raw data in both time and frequency domain and removed signals which associated with an exceptionally high correlation. We report experimental results with fully-polarimetric, single-pass interferometric dataset acquired by DLR's F-SAR sensor.

Global energy minimum structures and optoelectronic properties are presented for isolated Cdx Sey + clusters with x + y ≤ 26. The compositional- and size-dependent variation of optical, electronic and geometric properties is systematically studied within the framework of ground state and time-dependent density functional theory. The applied methods are justified by benchmarks with experimental data. It is shown that the optical gap can be tuned by more than 2 eV by only changing the composition for a fixed number of atoms. The stoichiometric species reveal an unexpected size-dependent behavior in comparison to larger colloidal CdSe quantum dots, that is, a redshift of the optical gap was observed with decreasing cluster size in contrast to predictions by quantum-size effects. This unexpected result is discussed in detail taking the positive charge of the clusters into account.

The synthesis of atomically precise clusters is nowadays well established. The study of isolated clusters in the gas phase has also become an approved field of research. Although both approaches examine the same research objects, namely nanoclusters, little is known about to what extent results from gas phase studies can be transferred to colloidal systems and vice versa. In particular, it is not yet sufficiently understood how ligands influence the geometric and electronic structure of clusters from an experimental point of view. By comparing a ligand-stabilized tin nanocluster in solution with an isolated species in the gas phase and considering different geometric arrangements with the same number of tin atoms, the impacts of ligand stabilization, molecular symmetry, and solvatochromism on the optical behavior are thoroughly worked out for the first time.

Molecular beam electric deflection experiments on neutral single copper-doped tin clusters are presented at different cryogenic nozzle temperatures. The experimental cluster beam profiles SnNCu (N = 9–16) are compared with classical rotational dynamic simulations of globally optimized structures obtained by a genetic algorithm based on density functional theory. The formation of endohedral complexes with comparable geometry to manganese- and gold-doped tin is confirmed. Theoretical methods predict ionic structures of the type Cuδ−@SnNδ+ with electron transfer from the tin cage to the central copper dopant. This behaviour is discussed based on a molecular orbital picture particularly with respect to other transition metal tetrel complexes.