Biomedical subjects

B Gumhalter

Publications and source records attributed to B Gumhalter.

10 recordsLinked to original sources

PubMed2006

Extreme ultrafast dynamics of quasiparticles excited in surface electronic bands.

We develop a many-body description of the nonadiabatic dynamics of quasiparticles in surface bands valid on an extremely ultrashort time scale by combining the formalism for the calculation of quasiparticle survival probabilities with the self-consistent treatment of the electronic response of the system. Applying this approach to the benchmark Cu(111) surface, we assess the behavior and intervals of preasymptotic electron and hole dynamics in surface bands and locate the transition to the asymptotic regime of the exponential quasiparticle decay characterized by the corrected Fermi golden rule-type of transition rate. The general validity of these findings enables distinguishing the various regimes of ultrafast electron dynamics that may be revealed in time resolved experiments.

Journal Article↗

PubMed2004

Entangled and disentangled decoherence of intermediate electron-hole pairs in two-photon photoemission from surface bands: beyond the adiabatic approximation.

We discuss the effects which combinations of entangled and disentangled decoherence and transient response induce on the early decay of coherent electron-hole pairs in the intermediate states of two-photon photoemission (2PPE) from image potential bands. We find that their interplay gives rise to deviations of the pair decay probabilities from simple exponential laws governed by independent quasiparticle lifetimes obtained in the self-energes based on the adiabatic hypothesis. Assessment of these effects for paradigmatic Cu(111) surface shows that they are most pronounced in the interval of pump-probe photon pulse delay times typical of current 2PPE experiments.

Journal Article↗

PubMed2003

Linear versus nonlinear coupling effects in single- and multiphonon atom-surface scattering.

We present a comparative assessment of the features of inelastic atom-surface scattering spectra that are produced by different forms of linear and nonlinear phonon coupling to the projectile atom. Starting from a simple theoretical model of atom-surface scattering and employing recently developed exact numerical and approximate analytical methods we calculate and compare the scattering probabilities ensuing from each form of interaction. This enables us to demonstrate that in the regime of thermal energy atom scattering from surfaces the dominant contributions to the zero-, one-, and multiphonon excitation probabilities arise from linear coupling treated to all orders in the interaction.

Journal Article↗

PubMed1995