Photoelectron jets and interference structures in ionization beyond dipole approximation: carrier- envelope phase effects and vortex streets

We have analyzed photoelectron jet formation in strong-field ionization using the hydrodynamic picture of quantum mechanics. We showed that von-Kármán-like vortex streets emerge in between jets in photoelectron momentum distributions. The spatial orientation of the jets can be controlled by tailoring the carrier-envelope phase of the driving laser pulse. This indicates that it is possible to experimentally measure emitted photoelectrons off the optical axis, which opens up new possibilities for high-frequency laser pulse diagnostics.

Block Copolymer-Templated, Single-Step Synthesis of Transition Metal Oxide Nanostructures for Sensing Applications

The synthesis of transition metal oxide nanostructures, thanks to their high surface-to-volume ratio and the resulting large fraction of surface atoms with high catalytic activity, is of prime importance for the development of new sensors and catalytic materials. Here, we report an economical, time-efficient, and easily scalable method of fabricating nanowires composed of vanadium, chromium, manganese, iron, and cobalt oxides by employing simultaneous block copolymer (BCP) self-assembly and selective sequestration of metal-organic acetylacetonate complexes within one of the BCP blocks. We discuss the mechanism and the primary factors that are responsible for the sequestration and conformal replication of the BCP template by the inorganic material that is obtained after the polymer template is removed. X-ray photoelectron spectroscopy (XPS) and powder X-ray diffraction (PXRD) studies indicate that the metal oxidation state in the nanowires produced by plasma ashing the BCP template closely matches that of the precursor complex and that their structure is amorphous, thus requiring high-temperature annealing in order to sinter them into a crystalline form. Finally, we demonstrate how the developed nanowire array fabrication scheme can be used to rapidly pattern a multilayered iron oxide nanomesh, which we then used to construct a prototype volatile organic compound sensor.