Shine a light: a circular dichroism effect in the ±10 % regime on randomly oriented chiral molecules in the gas phase is demonstrated. The signal is derived from images of photoelectron angular distributions produced by resonance-enhanced multiphoton ionization and allows the enantiomers to be distinguished. To date, this effect could only be generated with a synchrotron source. The new tabletop laser-based approach will make this approach far more accessible.

Mirror, mirror The ionization of chiral molecules with circularly polarized light creates an enhancement of the photoelectron angular distribution in the forward direction relative to the laser beam. The mirror‐image distribution is obtained with the mirror‐image enantiomer. The effect allows enantiomers to be distinguished in the gas phase. To date a synchrotron source was required, now as T. Baumert and co‐workers show in their Communication on only a laser set‐up is necessary.

Tetrazolium salts are exploited in various fields of research by virtue of their low reduction potentials. Increasingly, associated applications also attend to the photochemical and luminescence properties of these systems. Here, we investigate the photoinduced dynamics of phenyl-benzo[c]tetrazolo-cinnolinium chloride (PTC), one of the very few known fluorescent tetrazolium compounds, by using time-correlated single-photon counting, femtosecond fluorescence upconversion, and ultrafast transient absorption spectroscopy. PTC is generated photochemically by ultraviolet illumination of 2,3,5-triphenyl-tetrazolium chloride (TTC) in various alcohols. Time-resolved fluorescence measurements on PTC with different excitation wavelengths disclose biphasic solvation and vibrational relaxation dynamics. Depending on the solvent, the emission behavior of PTC is characterized by quantum yields on the order of several tens of percent and corresponding excited-state lifetimes of several hundreds of picoseconds. The radiative rate is basically constant for the studied alcohols, whereas the rate of the competing non-radiative process is sensitive to the solvent polarity. Hence, we discuss the possible involvement of intermediate radicals and further presumptive reaction pathways pursued after photoexcitation of PTC.

Schnelle und hoch empfindliche chirale Erkennung: Ein Zirkulardichroismus‐Effekt im Bereich von ±10 % an zufällig orientierten chiralen Molekülen in der Gasphase stammt aus Abbildungen von Photoelektronen‐Winkelverteilungen (siehe Bild), die über resonanzverstärkte Multiphoton‐Ionisation erzeugt wurden. Bisher konnte der Effekt nur an Synchrotronanlagen beobachtet werden, doch nun gelingt dies auch unter Verwendung eines kompakten Lasersystems.

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Femtosecond vortex beams with adjustable temporal pulse shapes are generated. These shaped laser pulses are characterized in the spectral domain by determination of the spectral amplitude and phase as well as in the spatial domain by expansion of the beam profile in a superposition of Laguerre-Gaussian transversal laser modes. The experiments demonstrate that the temporal pulse shapes impressed with a pulse shaper based on a programmable liquid-crystal spatial light modulator are basically unaltered by subsequent transmission through a spiral phase plate, while a high-quality optical vortex is imposed. The combination of programmable pulse shapes and optical vortices in femtosecond laser beams opens new possibilities for applications in micromachining, high harmonic generation, and microscopy.

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