On the applicability of the Caldeira-Leggett model and X-ray spectroscopy from a time-domain perspective

Datum

01.11.2016

Zeit

16:30 - 17:30

Sprecher

Sergei D. Ivanov

Zugehörigkeit

Rostock University)

Sprache

en

Hauptthema

Physik

Andere Themen

Physik

Beschreibung

The talk covers two independent topics stated in the title. The former concerns the concept of system-bath partitioning, which is a tempting idea based on identifying few important degrees of freedom and treating others approximately. A particular example is the Caldeira-Leggett (CL) model that corresponds to a harmonic bath bi-lineary coupled to the system part. This model is a cornerstone for many approaches ranging from fully quantum to purely classical. Here we investigate a general problem of mapping a real system onto a CL model [1-4]. It turns out, that the applicability of the model to cases with anharmonic system potentials is questionable due to the presence of the invertibility problem [1] unless the system itself resembles the CL model form. This might well be the case at surfaces or in the solid regime, as is shown for a highly relevant example of a hydrogen atom chemisorbed at graphene [4]. Further, we develop a Fourier-based parametrization method for the spectral densities that outperforms its time-domain analogues [2-3]. Very surprisingly, the widely used rigid bond method turns out to be inappropriate in general and leads to a systematic overestimation of relaxation times [2]. The latter topic focusses on nuclear dynamical effects in X-ray spectra. Here we develop a rigorous time-correlation method employing ground state molecular dynamics simulations [5]. In contrast to the first-order absorption, second-order resonant inelastic scattering spectra for gas phase water exhibit pronounced fingerprints of nuclear motions. The developed methodology does not depend on the accompanying electronic structure method in principle as well as on the spectral range and, thus, can be applied to, e.g., UV and X-ray photo-electron and Auger spectroscopies.

Letztmalig verändert: 01.11.2016, 08:47:06