Ultraviolet supercontinuum generation using a differentially-pumped integrated glass chip

We investigate the generation of ultrabroadband femtosecond ultraviolet (UV) radiation via third-order harmonic generation in highly confined gas media. A dual-stage differential-pumping scheme integrated into a glass microfluidic chip provides an exceptional gas confinement up to several bar and allows the apparatus to be operated under high-vacuum environment. UV pulses are generated both in argon and neon with up to ∼0.8 μJ energy and 0.2% conversion efficiency for spectra that cover the UVB and UVC regions between 200 and 325 nm. Numerical simulations based on the unidirectional pulse propagation equation reveal that ionization plays a critical role for extending the spectral bandwidth of the generated third-harmonic pulse beyond the tripled 800 nm driving laser pulse bandwidth. By delivering UV supercontinua supporting Fourier transform limits below 2 fs, as well as comparable pulse energies with respect to capillary-based techniques that typically provide high spectral tunability but produce narrower bandwidths, our compact device makes a step forward towards the production and application of sub-fs UV pulses for the investigation of electron dynamics in neutral molecules

Few-body Studies at Nuclotron-JINR

Recent results on the deuteron analyzing powers in dp- elastic scattering obtained at Nuclotron (JINR, Dubna) are compared with the calculations performed within relativistic multiple scattering model. The data demonstrate strong deviation form the predictions at large angles in the cm

Templated Assembly of Chiral Medium-Sized Cyclic Ethers via 8‑endo-trig Nucleophilic Cyclization of Cyclopropenes

An efficient approach toward enantioenriched eight-membered heterocycles via the intramolecular formal substitution of bromocyclopropanes with oxygen-based nucleophiles has been developed. The reaction proceeds via a reactive cyclopropene intermediate, which undergoes a rapid 8-<i>endo-trig</i> cyclization affording <i>cis</i>-fused [6.1.0] bicyclic products exclusively. The quaternary chiral center in the cyclopropene governs the configuration of the other two stereocenters in the final product

Ultraviolet supercontinuum generation using a differentially-pumped integrated glass chip

We investigate the generation of ultrabroadband femtosecond ultraviolet (UV) radiation via third-order harmonic generation in highly confined gas media. A dual-stage differential-pumping scheme integrated into a glass microfluidic chip provides an exceptional gas confinement up to several bar and allows the apparatus to be operated under high-vacuum environment. UV pulses are generated both in argon and neon with up to ∼0.8 μ J energy and 0.2% conversion efficiency for spectra that cover the UVB and UVC regions between 200 and 325 nm. Numerical simulations based on the unidirectional pulse propagation equation reveal that ionization plays a critical role for extending the spectral bandwidth of the generated third-harmonic pulse beyond the tripled 800 nm driving laser pulse bandwidth. By delivering UV supercontinua supporting Fourier transform limits below 2 fs, as well as comparable pulse energies with respect to capillary-based techniques that typically provide high spectral tunability but produce narrower bandwidths, our compact device makes a step forward towards the production and application of sub-fs UV pulses for the investigation of electron dynamics in neutral molecules

Ti-Modified Hydroxyapatites: Synthesis, Crystal Chemistry, and Photocatalytic Activity

The structural nature of photocatalytic properties of hydroxyapatites (HAp) synthesized from Ti-containing media (of Ti-modified hydroxyapatites) needs clarification. We synthesized hydroxyapatites from Ti-containing water solutions under various conditions and studied the received powder precipitations (before and after calcination at a temperature of 700 °C for 6 h) by a wide set of methods: powder X-ray diffraction (PXRD); vibrational, energy-dispersive X-ray, X-ray photoelectron, and diffuse reflectance spectroscopy; scanning electron microscopy, and gas phase photocatalytic activity tests. Analyzing the variations of unit cell parameters, we have proved that titanium is able to incorporate into the hydroxyapatite lattice in amounts of up to ∼10 wt % depending on synthesis conditions. At low concentrations (Ti/Ca ≤ 0.16), Ti4+ ions incorporate predominantly to the P site of hydroxyapatite structure. At higher concentrations (0.16 ≤ Ti/Ca ≤ 0.28), additional Ti4+ ions incorporate Ca sites. Besides, a significant share of titanium forms predominantly amorphous impurity phases, which transform into crystalline TiO2 (anatase and rutile) upon calcination and are often undetectable by PXRD. The presence of crystalline titanium oxides (anatase and rutile) has a crucial effect on photocatalytic activity of calcined Ti-modified hydroxyapatites. Synthesized HAp/TiO2 compositions are biocompatible heterostructured materials with photocatalytic activity comparable to that of commercial photocatalysts and could be recommended for medical–biological applications