TY  - JOUR
A1  - Nacci, Christophe
A1  - Foelsch, Stefan
A1  - Zenichowski, Karl
A1  - Dokic, Jadranka
A1  - Klamroth, Tillmann
A1  - Saalfrank, Peter
T1  - Current versus temperature-induced switching in a single-molecule tunnel junction : 1,5 cyclooctadiene on Si(001)
N2  - The biconformational switching of single cyclooctadiene molecules chemisorbed on a Si(001) surface was explored by quantum chemical and quantum dynamical calculations and low-temperature scanning tunneling microscopy experiments. The calculations rationalize the experimentally observed switching driven by inelastic electron tunneling (IET) at 5 K. At higher temperatures, they predict a controllable crossover behavior between IET-driven and thermally activated switching, which is fully confirmed by experiment.
Y1  - 2009
UR  - http://pubs.acs.org/journal/nalefd
U6  - https://doi.org/10.1021/Nl901419g
SN  - 1530-6984
ER  - 
TY  - JOUR
A1  - Zenichowski, Karl
A1  - Dokic, Jadranka
A1  - Klamroth, Tillmann
A1  - Saalfrank, Peter
T1  - Current versus temperature-induced switching of a single molecule -  open-system density matrix theory for 1,5-cyclooctadiene on Si(100)
JF  - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr
N2  - The switching of single cyclooctadiene molecules chemisorbed on a Si(100) surface between two stable conformations, can be achieved with a scanning tunneling microscope [Nacci , Phys. Rev. B 77, 121405(R) (2008)]. Recently, it was shown by quantum chemical and quantum dynamical simulations that major experimental facts can be explained by a single-mode model with switching enforced by inelastic electron tunneling (IET) excitations and perturbed by vibrational relaxation [Nacci , Nano Lett. 9, 2997 (2009)]. In the present paper, we extend the previous theoretical work in several respects: (1) The model is generalized to a two-mode description in which two C2H4 units of COD can move independently; (2) contributions of dipole and, in addition, (cation and anion) resonance-IET rates are considered; (3) the harmonic-linear vibrational relaxation model used previously is generalized to anharmonic vibrations. While the present models highlight generic aspects of IET-switching between two potential minima, they also rationalize specific experimental findings for COD/Si(100): (1) A single-electron excitation mechanism with a linear dependence of the switching rate on tunneling current I, (2) the capability to switch both at negative and positive sample biases, and (3) a crossover temperature around similar to 60 K from an IET-driven, T-independent atom tunneling regime, to classical over-the-barrier isomerization with exponential T-dependence at higher temperatures for a bias voltage of +1.5 V and an average tunneling current of 0.73 nA.
Y1  - 2012
U6  - https://doi.org/10.1063/1.3692229
SN  - 0021-9606
VL  - 136
IS  - 9
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Füchsel, Gernot
A1  - Tremblay, Jean Christophe
A1  - Klamroth, Tillmann
A1  - Saalfrank, Peter
T1  - Selective excitation of molecule-surface vibrations in H2 and D2 dissociatively adsorbed on Ru(0001)
JF  - Israel journal of chemistry
N2  - In this contribution we report about the selective vibrational excitation of H2 and D2 on Ru(0001) as an example for nonadiabatic coupling of an open quantum system to a dissipative environment. We investigate the possibility of achieving state-selective vibrational excitations of H2 and D2 adsorbed on a Ru(0001) surface using picosecond infrared laser pulses. The systems behavior is explored using pulses that are rationally designed and others that are optimized using a time-local variant of Optimal Control Theory. The effects of dissipation on the laser-driven dynamics are studied using the reduced-density matrix formalism. The non-adiabatic couplings between adsorbate and surface are computed perturbatively, for which our recently introduced state-resolved anharmonic rate model is used. It is shown that mode- and state-selective excitation can be achieved in the absence of dissipation when using optimized laser pulses. The inclusion of dissipation in the model reduces the state selectivity and the population transfer yield to highly excited states. In this case, mode activation is most effectively realized by a rational pulse of carefully chosen duration rather than by a locally optimized pulse.
KW  - dissipative dynamics
KW  - photochemistry
KW  - quantum control
KW  - surface chemistry
Y1  - 2012
U6  - https://doi.org/10.1002/ijch.201100097
SN  - 0021-2148
VL  - 52
IS  - 5
SP  - 438
EP  - 451
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Saalfrank, Peter
A1  - Klamroth, Tillmann
A1  - Huber, C.
A1  - Krause, Pascal
T1  - Laser-driven electron dynamics at interfaces
N2  - In this paper we present time-dependent, quantum-dynamical simulations of photoinduced processes at solid surfaces involving nonadiabatic transitions of electrons to and from short-lived intermediate excited states. In particular, two-photon photoemission (2PPE) spectra of naked metal surfaces and free-standing metal films are considered. One major problem in both cases is the presence of electron-electron scattering, which is treated here in various ways. The first way is to adopt an open-system density matrix approach, in which a single electron is weakly coupled to a "bath" of other electrons. The second approach is based on a many-electron Schrodinger equation, which is solved with the help of a time-dependent configuration interactions singles (TD-CIS) method
Y1  - 2005
SN  - 0021-2148
ER  - 
TY  - JOUR
A1  - Schwarze, Thomas
A1  - Dosche, Carsten
A1  - Flehr, Roman
A1  - Klamroth, Tillmann
A1  - Löhmannsröben, Hans-Gerd
A1  - Saalfrank, Peter
A1  - Cleve, Ernst
A1  - Buschmann, Hans-Jürgen
A1  - Holdt, Hans-Jürgen
T1  - Combination of a CT modulated PET and an intramolecular excimer formation to quantify PdCl2 by large fluorescence enhancement
N2  - The [6.6](9,10)anthracenophane 1 (Scheme 1) is a selective fluoroionophore for the detection of PdCl2 with a large fluorescence enhancement factor (I/I-0 > 250).
Y1  - 2010
UR  - http://pubs.rsc.org/en/content/articlehtml/2010/cc/b919973j
U6  - https://doi.org/10.1039/B919973j
SN  - 1359-7345
ER  - 
TY  - JOUR
A1  - Nest, Mathias
A1  - Klamroth, Tillmann
A1  - Saalfrank, Peter
T1  - The multiconfiguration time-dependent Hartree-Fock method for quantum chemical calculations
N2  - We apply the multiconfiguration time-dependent Hartree-Fock method to electronic structure calculations and show that quantum chemical information can be obtained with this explicitly time-dependent approach. Different equations of motion are discussed, as well as the numerical cost. The two-electron integrals are calculated using a natural potential expansion, of which we describe the convergence behavior in detail
Y1  - 2005
SN  - 0021-9606
ER  - 
TY  - JOUR
A1  - Schwarze, Thomas
A1  - Dosche, Carsten
A1  - Flehr, Roman
A1  - Klamroth, Tillmann
A1  - Löhmannsröben, Hans-Gerd
A1  - Saalfrank, Peter
A1  - Cleve, Ernst
A1  - Buschmann, Hans-Jürgen
A1  - Holdt, Hans-Jürgen
T1  - Combination of a CT modulated PET and an intramolecular excimer formation to quantify PdCl2 by large fluorescence enhancement
Y1  - 2010
UR  - http://www.rsc.org/ej/CC/2010/b919973j.pdf
SN  - 1359-7345
ER  - 
TY  - JOUR
A1  - Schwarze, Thomas
A1  - Mueller, Holger
A1  - Dosche, Carsten
A1  - Klamroth, Tillmann
A1  - Mickler, Wulfhard
A1  - Kelling, Alexandra
T1  - Luminescence detection of open-shell transition-metal ions by photoinduced electron transfer controlled by internal charge transfer of a receptor
Y1  - 2007
UR  - http://onlinelibrary.wiley.com/doi/10.1002/ange.200603992/pdf
U6  - https://doi.org/10.1002/anie.200603992
ER  - 
TY  - JOUR
A1  - Zenichowski, Karl
A1  - Nacci, Ch
A1  - Fölsch, S.
A1  - Dokic, Jadranka
A1  - Klamroth, Tillmann
A1  - Saalfrank, Peter
T1  - STM-switching of organic molecules on semiconductor surfaces: an above threshold density matrix model for 1,5 cyclooctadiene on Si(100)
JF  - Journal of physics : Condensed matter
N2  - The scanning tunnelling microscope (STM)-induced switching of a single cyclooctadiene molecule between two stable conformations chemisorbed on a Si(100) surface is investigated using an above threshold model including a neutral ground state and an ionic excited state potential. Switching was recently achieved experimentally with an STM operated at cryogenic temperatures (Nacci et al 2008 Phys. Rev. B 77 121405(R)) and rationalized by a below threshold model using just a single potential energy surface (Nacci et al 2009 Nano Lett. 9 2997).
 In the present paper, we show that experimental key findings on the inelastic electron tunnelling (IET) switching can also be rationalized using an above threshold density matrix model, which includes, in addition to the neutral ground state potential, an anionic or cationic excited potential. We use one and two-dimensional potential energy surfaces. Furthermore, the influence of two key parameters of the density matrix description, namely the electronic lifetime of the ionic resonance and the vibrational lifetimes, on the ground state potential are discussed.
Y1  - 2012
U6  - https://doi.org/10.1088/0953-8984/24/39/394009
SN  - 0953-8984
VL  - 24
IS  - 39
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Bronner, C.
A1  - Leyssner, F.
A1  - Stremlau, S.
A1  - Utecht, Manuel Martin
A1  - Saalfrank, Peter
A1  - Klamroth, Tillmann
A1  - Tegeder, P.
T1  - Electronic structure of a subnanometer wide bottom-up fabricated graphene nanoribbon: End states, band gap, and dispersion
JF  - Physical review : B, Condensed matter and materials physics
N2  - Angle-resolved two-photon photoemission and high-resolution electron energy loss spectroscopy are employed to derive the electronic structure of a subnanometer atomically precise quasi-one-dimensional graphene nanoribbon (GNR) on Au(111). We resolved occupied and unoccupied electronic bands including their dispersion and determined the band gap, which possesses an unexpectedly large value of 5.1 eV. Supported by density functional theory calculations for the idealized infinite polymer and finite size oligomers, an unoccupied nondispersive electronic state with an energetic position in the middle of the band gap of the GNR could be identified. This state resides at both ends of the ribbon (end state) and is only found in the finite sized systems, i.e., the oligomers.
Y1  - 2012
U6  - https://doi.org/10.1103/PhysRevB.86.085444
SN  - 1098-0121
VL  - 86
IS  - 8
PB  - American Physical Society
CY  - College Park
ER  -