The Reaction Microscope: Imaging and Pulse Shaping Control in Photodynamics

Abstract

Herein, we review the current capabilities and potential of advanced single-particle imaging techniques to study photodynamics in isolated molecules. These reaction microscopes are able to measure the full three-dimensional energy and angular distribution of (correlated) particles such as electrons and molecular fragments ejected after photoexcitation of molecules. In particular, we discuss the performance and capabilities of a novel photoelectron-photoion coincidence imaging spectrometer constructed at LaserLaB Amsterdam. This microscope was developed for the study of nonadiabatic effects in ultrafast time-resolved experiments. It is specifically targeted at optimal control studies of photodynamics to foster and advance our understanding of mechanisms in optimal control with shaped ultrafast laser pulses. We review a few recent experimental results illustrating the wealth of detailed information that can be obtained in such imaging experiments about the interplay between (shaped) laser fields, molecular dynamics, ionization processes and competing multichannel pathways. Furthermore, the recently developed photoelectron-circular-dichroism imaging technique to detect enantiomers and to study chirality effects will be discussed, as a further illustration of the potential of modern reaction microscopes in stereochemistry.

Probing chirality with a femtosecond reaction microscope

“…This chiral asymmetry in the photoelectron angular distribution using This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. [5][6][7] can be used to detect mass-selected chiral molecules with high selectivity and sensitivity with our results on the chiral molecule camphor.…”

“…The detection setup consists of a state of the art coincidence imaging setup for photoelectrons and photoions using the velocity map imaging technique. Both the electron and the coincident ion were detected on a single Micro-Channel-Plate delay-line detector, by switching the High-Voltages (HV) on the ion optics of the Velocity-Map-Ion (VMI) lenses [5][6][7]. Initial experiments were done on the two enantiomers of camphor that were obtained commercially (Sigma-Aldrich, purity 98% (R) and 99% (S)) and were contained in two separate tubes in vacuum lines outside the coincidence imaging setup.…”

Wavelength dependent photoelectron circular dichroism of limonene studied by femtosecond multiphoton laser ionization and electron-ion coincidence imaging

“…The electron-ion coincidence imaging spectrometer that was used in this work has been described in detail before 20,21 and we will only discuss the most relevant parts for the present study. A schematic of the set-up is shown in Fig.…”

Photoelectron Circular Dichroism of Bicyclic Ketones from Multiphoton Ionization with Femtosecond Laser Pulses

“…From a data acquisition and analysis point of view, Janssen and coworkers applied the coincidence technique [78,79] and measured the central section of the PAD. This time sliced electron image is a projection of photoelectrons with an ejection angle of AE 258 with respect to the centre of the image and the plane parallel to the detector surface.…”