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Multiple structure formation and molecule dynamics in transient plasmas generated by laser ablation of graphite
摘要： Transient plasmas generated by ns - laser ablation of graphite in air have been investigated by complementary optical diagnosis techniques to study complex multiple structures generated in carbon laser produced plasmas (C-LPP) during the expansion phase. The overall emission was investigated by ICCD fast camera imaging and revealed the structuring of C-LPP into four distinct structures with di?erent evolutions. The dynamic of the C-LPP was analyzed on various expansion directions in order to understand the formation of the main CN dominant structure and of lateral “?aps” with dominant C2 emission. The kinetic and thermal energies of the resulted atoms, ions and molecules were investigated by means of space-and time-resolved optical emission spectroscopy and using the Boltzmann plot and Stark broadening approaches. The e?ect of the background gas pressure on the formation of molecular carbon structures is discussed and an optimum range of working pressure which maximizes the generation of C2 is found. Based on the acquired data a scenario for the complex carbon structures generation in C-PLL as function of the background gas is proposed.
关键词： Complex carbon structures,ns-laser produced plasma,molecule dynamics,Graphite,Multiple plasma structuring,ICCD fast camera imaging
更新于2025-09-16 10:30:52
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Diffracted X-ray Blinking Tracks Single Protein Motions
摘要： Single molecule dynamics studies have begun to use quantum probes. Single particle analysis using cryo-transmission electron microscopy has dramatically improved the resolution when studying protein structures and is shifting towards molecular motion observations. X-ray free-electron lasers are also being explored as routes for determining single molecule structures of biological entities. Here, we propose a new X-ray single molecule technology that allows observation of molecular internal motion over long time scales, ranging from milliseconds up to 103 seconds. Our method uses both low-dose monochromatic X-rays and nanocrystal labelling technology. During monochromatic X-ray diffraction experiments, the intensity of X-ray diffraction from moving single nanocrystals appears to blink because of Brownian motion in aqueous solutions. X-ray diffraction spots from moving nanocrystals were observed to cycle in and out of the Bragg condition. Consequently, the internal motions of a protein molecule labelled with nanocrystals could be extracted from the time trajectory using this diffracted X-ray blinking (DXB) approach. Finally, we succeeded in distinguishing the degree of fluctuation motions of an individual acetylcholine-binding protein (AChBP) interacting with acetylcholine (ACh) using a laboratory X-ray source.
关键词： Acetylcholine-binding protein,Brownian motion,Nanocrystal labelling,Single molecule dynamics,X-ray diffraction
更新于2025-09-09 09:28:46