Tracing orbital images on ultrafast time scales

Frontier orbitals determine fundamental molecular properties such as chemical reactivities. Although electron distributions of occupied orbitals can be imaged in momentum space by photoemission tomography, it has so far been impossible to follow the momentum-space dynamics of a molecular orbital in time, for example through an excitation or a chemical reaction. Here, we combined time-resolved photoemission using high laser harmonics and a momentum microscope to establish a tomographic, femtosecond pump-probe experiment of unoccupied molecular orbitals. We measured the full momentum-space distribution of transiently excited electrons, connecting their excited-state dynamics to real-space excitation pathways. Because in molecules this distribution is closely linked to orbital shapes, our experiment may in the future offer the possibility to observe ultrafast electron motion in time and space.

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Photoionization of Ca atoms in a time resolved pump-probe experiment with synchronized undulator- and Ti:Saphir laser pulses

Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment ◽

10.1016/0168-9002(95)00559-5 ◽

1995 ◽

Vol 365 (2-3) ◽

pp. 603-606 ◽

Cited By ~ 7

Author(s):

J. Gatzke ◽

R. Bellmann ◽

I. Hertel ◽

M. Wedowski ◽

K. Godehusen ◽

...

Keyword(s):

Laser Pulses ◽

Time Resolved ◽

Pump Probe ◽

Probe Experiment ◽

Pump Probe Experiment

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Nonlinear Mechanisms in Carbon-Black Suspension in a Limiting Geometry

MRS Proceedings ◽

10.1557/proc-479-293 ◽

1997 ◽

Vol 479 ◽

Cited By ~ 2

Author(s):

Francois Fougeanet ◽

Jean-Claude Fabre

Keyword(s):

Carbon Black ◽

Optical Limiting ◽

Plasma Emission ◽

Time Resolved ◽

Pump Probe ◽

Limiting Behavior ◽

Plasma Effects ◽

Probe Experiment ◽

Probe Transmission ◽

Pump Probe Experiment

AbstractAlthough Carbon-Black suspensions (CBS) have been studied extensively for optical limiting applications, the microscopic mechanisms responsible for their limiting behavior still remain unclear. To study the mechanisms leading to the nonlinearity, we have performed a pump-probe experiment coupled with plasma emission measurements. Time resolved probe transmission have permitted to differentiate bubbles from plasma effects in the case of Carbon-Black in CS2. Other effects are discussed in terms of limiting performance.

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Effective data collection and refinement of pertubated structures

Acta Crystallographica Section A Foundations and Advances ◽

10.1107/s2053273314082497 ◽

2014 ◽

Vol 70 (a1) ◽

pp. C1750-C1750

Author(s):

Pascal Parois ◽

Richard Cooper

Keyword(s):

Excited State ◽

Data Collection ◽

Least Squares ◽

Time Resolved ◽

Pump Probe ◽

Partial Data ◽

Mixed Oxidation ◽

Probe Experiment ◽

Pump Probe Experiment

Approaches to determining the influence of individual measurements on the precision of crystallographic least squares parameters have been known for a long while.[1] Situations in which the precision of a single parameter (or linear combination of parameters) is critical can include: determination of novel bond lengths; refinement of site occupancies in mixed metal or mixed oxidation state systems; determination of the fraction of excited state molecules in a time-resolved pump-probe experiment. Such calculations are easily applicable to point-detector instruments, where individual influential reflections could be remeasured one-by-one. However, on a modern area detector instrument many reflections are measured on one frame and therefore some consideration of the appropriate strategy of reciprocal space scans is permitted to allow a more efficient use of the instrument. The highly influential partial data collection is then feed into an appropriate refinement model. Occupancies in mixed-metal or mixed-oxidation state systems and fractions and positions of excited state molecules during a time-resolved pump-probe experiment can be determined using direct refinement of the perturbation of the structure from the ground state. Re-factoring to modern Fortran of the Crystals software is in progress to allow the implementation of new algorithms such as a difference refinement.[2] We present an analysis of diffractometer strategy selection to prioritize scans which give the best improvement in specific least-squares parameters and a novel algorithm for the refinement of the partial data using crystals.

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