TY  - JOUR
A1  - Tremblay, Jean Christophe
A1  - Krause, Pascal
A1  - Klamroth, Tillmann
A1  - Saalfrank, Peter
T1  - Time-dependent response of dissipative electron systems
N2  - We present a systematic study of the influence of energy and phase relaxation on dynamic polarizability simulations in the linear response regime. The nonperturbative approach is based on explicit electron dynamics using short laser pulses of low intensities. To include environmental effects on the property calculation, we use the time- dependent configuration-interaction method in its reduced density matrix formulation. Both energy dissipation and nonlocal pure dephasing are included. The explicit treatment of time-resolved electron dynamics gives access to the phase shift between the electric field and the induced dipole moment, which can be used to define a useful uncertainty measure for the dynamic polarizability. The nonperturbative treatment is compared to perturbation theory expressions, as applied to a simple model system, the rigid H-2 molecule. It is shown that both approaches are equivalent for low field intensities, but the time-dependent treatment provides complementary information on the phase of the induced dipole moment, which allows for the definition of an uncertainty associated with the computation of the dynamic polarizability in the linear response regime.
Y1  - 2010
UR  - http://pra.aps.org/
U6  - https://doi.org/10.1103/Physreva.81.063420
SN  - 1050-2947
ER  - 
TY  - JOUR
A1  - Füchsel, Gernot
A1  - Klamroth, Tillmann
A1  - Tremblay, Jean Christophe
A1  - Saalfrank, Peter
T1  - Stochastic approach to laser-induced ultrafast dynamics : the desorption of H-2/D-2 from Ru(0001)
N2  - The desorption of molecular hydrogen and deuterium induced by femtosecond-laser pulses is studied theoretically for the so-called DIMET (Desorption Induced by Multiple Electronic Transitions) process. These investigations are based on nonadiabatic classical Monte Carlo trajectory (CMCT) simulations on a ground and an excited state potential energy surface, including up to all six adsorbate degrees of freedom. The focus is on the hot-electron mediated energy transfer from the surface to the molecule and back, and the energy partitioning between the different degrees of freedom of the desorbing molecules. We first validate for a two-mode model comprising the desorption mode and the internal vibrational coordinate, the classical Monte Carlo trajectory method by comparing with Monte Carlo wavepacket (MCWP) calculations arising from a fully quantum mechanical open-system density matrix treatment. We then proceed by extending the CMCT calculations to include all six nuclear degrees of freedom of the desorbing molecule. This allows for a detailed comparison between theory and experiment concerning isotope effects, energy partitioning (translational, vibrational, and rotational energies and their distributions), and the dependence of these properties on the laser fluence. The most important findings are as follows. (i) CMCT agrees qualitative with the MCWP scheme. (ii) The basic experimental features such as the large isotope effect, the non-linear increase of yield with laser fluence, translationally hot products (in the order of several 1000 K) and non-equipartitioning of translational and internal energies (E-trans > E- vib > E-rot) are well reproduced. (iii) Predictions concerning a strong angular dependence of translational energies at large observation angles are also made.
Y1  - 2010
UR  - http://xlink.rsc.org/jumptojournal.cfm?journal_code=CP
U6  - https://doi.org/10.1039/C0cp00895h
SN  - 1463-9076
ER  - 
TY  - JOUR
A1  - Tremblay, Jean Christophe
A1  - Monturet, Serge
A1  - Saalfrank, Peter
T1  - Electronic damping of anharmonic adsorbate vibrations at metallic surfaces
N2  - The nonadiabatic coupling of an adsorbate close to a metallic surface leads to electronic damping of adsorbate vibrations and line broadening in vibrational spectroscopy. Here, a perturbative treatment of the electronic contribution to the lifetime broadening serves as a building block for a new approach, in which anharmonic vibrational transition rates are calculated from a position-dependent coupling function. Different models for the coupling function will be tested, all related to embedding theory. The first two are models based on a scattering approach with (i) a jellium-type and (ii) a density functional theory based embedding density, respectively. In a third variant a further refined model is used for the embedding density, and a semiempirical approach is taken in which a scaling factor is chosen to match harmonic, single-site, first-principles transition rates, obtained from periodic density functional theory. For the example of hydrogen atoms on (adsorption) and below (subsurface absorption) a Pd(111) surface, lifetimes of and transition rates between vibrational levels are computed. The transition rates emerging from different models serve as input for the selective subsurface adsorption of hydrogen in palladium starting from an adsorption site, by using sequences of infrared laser pulses in a laser distillation scheme.
Y1  - 2010
UR  - http://prb.aps.org/
U6  - https://doi.org/10.1103/Physrevb.81.125408
SN  - 1098-0121
ER  -