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High Energy and Short Pulse Lasers || Brilliance Improvement of a Laser-Produced Soft X-Ray Plasma
摘要： The brilliance of a laser-produced soft X-ray source is enhanced for gaseous target concepts. In contrast to solid or liquid target materials, these sources are clean and versatile but provide a comparably low conversion efficiency of laser energy into EUV and soft X-ray radiation. The basic idea is to induce supersonic effects in the gas jet, leading to a local increase of the particle density, and thus, to a larger number of possible emitters. Typically, the target gas is expanded into a vacuum environment and the density rapidly drops in all directions. In the present approach, a low pressure helium atmosphere is used to generate shock waves in the supersonic nozzle flow. Passing through these structures, the target gas is recompressed, and the particle density is raised. By focusing the laser beam into such regions, a higher number of gas atoms can be ionized resulting in a brighter and smaller plasma.
关键词： soft X-ray,supersonic jet,barrel shock,laser-produced plasma
更新于2025-09-16 10:30:52
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Controlled transition of microcapsules from coil conformation to globule during the expansion of the pulse jet of nanoparticle suspension of TiO2 in supercritical (CO2) polyethylene glycol solution
摘要： The process of microencapsulation of titanium dioxide nanoparticles during the expansion of a supersonic jet of TiO2 suspension in a solution of polyethylene glycol (PEG 8000) in supercritical CO2 into a vacuum and background gas (helium) has been studied experimentally. The dependence of the position of the microcapsule transition point on the jet axis from the coil to a globular conformation on the temperature in the reactor and on the pressure of the background gas at different co-solvent concentrations has been established. A “coil?globule” re-entrant transition has been recorded at a greater distance from the nozzle exit than the point of collapse.
关键词： supersonic jet,polyethylene glycol,microencapsulation,supercritical CO2,coil-globule transition,titanium dioxide
更新于2025-09-12 10:27:22
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Induced Circular Dichroism of Jet-Cooled Phenol Complexes with <i>R</i> -(–)-2-Butanol
摘要： The induced circular dichroism (ICD) of phenol complexed with R-(–)-2-butanol (PhOH-(–)BOH) in a supersonic jet is investigated using resonant two-photon ionization CD (R2PICD) spectroscopy. The R2PICD spectrum of PhOH-(–)BOH exhibits nonzero ICD bands near the absorption region of bare PhOH, where (–)BOH is transparent. Two different conformers containing a single hydrogen bond between PhOH and (–)BOH are identified using ultraviolet(UV)-UV hole-burning and infrared (IR) ion-dip spectroscopy combined with quantum theoretical calculations. The ICD values of the two conformers are similar to each other. To understand these similar ICD effects of the conformers, the geometrical asymmetry of the PhOH moiety bound to (–)BOH and the coupling strength of the electric transition dipole moments between PhOH and (–)BOH are estimated. Comparing the ICD values of PhOH-(–)BOH with those of PhOH-(–)-L-methyl lactate in the previous report (Hong, A.; Moon, C. J.; Jang, H.; Min, A.; Choi, M. Y.; Heo, J.; Kim, N. J. J. Phys. Chem. Lett. 2018, 9, 476-480), we investigate the physical properties that may govern the differences of the ICD values between the two complexes.
关键词： R-(–)-2-Butanol,Phenol Complexes,Supersonic Jet,Resonant Two-Photon Ionization CD Spectroscopy,Induced Circular Dichroism
更新于2025-09-12 10:27:22
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A new approach to studying the luminescence spectra of free icosahedral and crystalline argon nanoclusters
摘要： We propose a new approach to analyzing the cathodoluminescence spectra of free argon nanoclusters, forming in a supersonic jet flowing into vacuum. Based on this approach, we conduct an analysis of the intensities of the luminescence bands of neutral and charged excimer complexes (Ar2)* and (Ar+4)*, measured for clusters with an average size ranging from 500 to 8900 atoms per cluster, and a diameter of 32–87 A? . It is shown that the concentration of the substance condensed into clusters, which determines the integrated intensity of the bands, is proportional to the logarithm of the average size of the clusters in the jet. An analysis of the normalized intensities of the (Ar2)* and (Ar+4)* bands for crystalline clusters with an fcc structure allowed us to establish that the luminescence of neutral (Ar2)* molecules comes from within the volume of the cluster, while the charged complexes (Ar+4)* emit from the subsurface layer. We highlighted an area of cluster dimensions at which the jet is dominated by quasi-crystalline clusters with an icosahedral structure, and it is shown that the transition from icosahedral clusters to fcc structures occurs when the average size of the cluster in the jet is (cid:2)N = (1000–1800) atoms/cluster.
关键词： cathodoluminescence,argon nanoclusters,luminescence spectra,excimer complexes,supersonic jet
更新于2025-09-04 15:30:14