Modelling human choices: MADeM and decision‑making

Research supported by FAPESP 2015/50122-0 and DFG-GRTK 1740/2. RP and AR are also part of the Research, Innovation and Dissemination Center for Neuromathematics FAPESP grant (2013/07699-0). RP is supported by a FAPESP scholarship (2013/25667-8). ACR is partially supported by a CNPq fellowship (grant 306251/2014-0)

Aufbau eines hochauflösenden Elektronenenergieverlustspektrometers mit integriertem Rastertunnelmikroskop : potentielle Einsatzmöglichkeiten erläutert am Beispiel der Ostwald-Reifung von Kupferinseln auf Cu(100) und der Reaktionen von Kalium auf Pt(111)-Flächen

This thesis deals with the investigation of diffusion processes and surface reactions on metal surfaces by means of scanning tunneling micoroscopy (STM) and electron energy loss spectroscopy (EELS). A new combined STM/EELS ultra high vacuum apparatus has been set up which allows surface imaging and surface vibrational spectroscopy without sample transfer. The tunneling microscope is integrated in the scattering chamber of the electron spectrometer so that the tunneling tip is able to scan the sample surface while the electron beam is scattered at the latter simultaneously. The sample can be cooled down below 30 K and heated to 1300 K . First measurements show that the vibrational isolation of the sample and the performance of the STM ("beetle type") have to be improved in the future. The Ostwald ripening of two dimensional Cu adatom islands on the Cu(100) surface has been followed with STM between 333 and 413 K. By considering the time dependence of the sizes of individual islands the mechanism for the ripening is characterized. The result is unexpected for a simple metal surface: The flow of atoms from one island to another is limited by attachment-detachment kinetics at the island edges. To explain this result, it is proposed that the transport of atoms between the islands occurs by vacancy rather than by adatom diffusion. From the temparature dependence of the island decay the activation energy is found to be E$_{act}$ 0.80 $\pm$ 0.03 eV. EELS and STM have been used to characterize the adsorption of potassium on Pt(111) surfaces at room temparature. The STM results indicate an incorporation of potassium at the platinum surface, especially at steps. The EELS data show no definite evidence for potassium bound in a subsurface site. The vibrational frequency of adsorbed potassium adatoms shifts from 135 cm$^{-1}$ at low coverages to 175 cm$^{-1}$ at a coverage of $\theta_{K}$ = 0.16. This frequency shift can be explained by lateral dipole-dipole interactions between the adsorbed alkali metal atoms. For potassium coverages up to $\theta_{K}$ = 0.33, the frequency decreases to 155 cm$^{-1}$ and the loss intensity nearly vanishes which is attributed to the metallization of the alkali metal layer. Above potassium coverages of about $\theta_{K}$ = 0.10 the adsorbed potassium reacts with residual water molecules to form potassium hydroxide, with the potassium atom bonding to the platinum