Quasi-phase matching of high-order harmonic generation at high photon energies using counterpropagating pulses

We extend all-optical quasi-phase matching of high-order harmonic generation into spectral regions where conventional phase matching is not possible. The high laser intensities required to generate harmonics at energy >130 eV, coupled with the resulting high level of ionization, preclude conventional phase matching in all nonlinear media. Selective enhancement factors between 40 and 150 in the flux of harmonics at photon energies around 140 eV are demonstrated using a train of two counterpropagating pulses.     

Untersuchung von Getreide, Mehl und Mehlerzeugnissen

Ohne Zusammenfassung     

Bright, coherent, ultrafast soft X-ray harmonics spanning the water window from a tabletop light source

We demonstrate fully phase-matched high harmonic emission spanning the water window spectral region important for nano- and bioimaging and a breadth of materials and molecular dynamics studies. We also generate the broadest bright coherent bandwidth (≈300 eV) to date from any light source, small or large, that is consistent with a single subfemtosecond burst. The harmonic photon flux at 0.5 keV is 103 higher than demonstrated previously. This work extends bright, spatially coherent, attosecond pulses into the soft x-ray region for the first time.     

A practical chiral bicyclic thioglycolate lactam auxiliary for stereoselective quaternary carbon formation

[reaction: see text] Chiral bicyclic thioglycolate lactams may be prepared in three steps from inexpensive commercial materials. The resulting lactams may be alkylated three times, twice using basic enolization and once using reductive enolization, to form alpha-quaternary carboxylic acid derivatives in high yield and with high diastereoselectivity. The alkylation products may be cleaved under either acidic or reductive conditions to furnish either carboxylic acids or primary alcohols, respectively.     

Nouveaux byssoméruliols de Byssomerulius corium(Fr.) Parm.

Fruit-bodies and mycelia of Byssomerulius corium (Fr.)Parm. contain a large quantity (ca. 18 and 5–12% respectively of dry weight) of byssomeruliols, new phloracetophenone derivatives. Structures were elucidated by spectroscopic methods with emphasis on mass spectrometry. These compounds appear to be restricted so far to this species.