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Focal overlap gating in velocity map imaging to achieve high signal-to-noise ratio in photo-ion pump-probe experiments
摘要： We demonstrate a technique in velocity map imaging (VMI) that allows spatial gating of the laser focal overlap region in time resolved pump-probe experiments. This significantly enhances signal-to-noise ratio by eliminating background signal arising outside the region of spatial overlap of pump and probe beams. This enhancement is achieved by tilting the laser beams with respect to the surface of the VMI electrodes which creates a gradient in flight time for particles born at different points along the beam. By suitably pulsing our microchannel plate detector, we can select particles born only where the laser beams overlap. This spatial gating in velocity map imaging can benefit nearly all photo-ion pump-probe VMI experiments especially when extreme-ultraviolet light or X-rays are involved which produce large background signals on their own.
关键词： signal-to-noise ratio,pump-probe experiments,X-rays,extreme-ultraviolet light,velocity map imaging,spatial gating
更新于2025-09-04 15:30:14
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Optimization and Characterization of High-Harmonic Generation for Probing Solid Density Plasmas
摘要： The creation of high energy density plasma states produced during laser–solid interaction on a sub-picosecond timescale opens a way to create astrophysical plasmas in the lab to investigate their properties, such as the frequency-dependent refractive index. Available probes to measure absorption and phase-changes given by the complex refractive index of the plasma state are extreme-UV (EUV) and soft X-ray (XUV) ultra-short pulses from high harmonic generation (HHG). For demanding imaging applications such as single-shot measurements of solid density plasmas, the HHG probe has to be optimized in photon number and characterized in intensity and wavefront stability from shot-to-shot. In an experiment, a coherent EUV source based on HHG driven by a compact diode-pumped laser is optimized in photons per pulse for argon and xenon, and the shot-to-shot intensity stability and wavefront changes are characterized. The experimental results are compared to an analytical model estimating the HHG yield, showing good agreement. The obtained values are compared to available data for solid density plasmas to con?rm the feasibility of HHG as a probe.
关键词： pump-probe,XUV,diode-pumped lasers,high energy density physics,high-harmonic generation
更新于2025-09-04 15:30:14
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Co-localization coefficients of a target-switchable fluorescent probe can serve as an indicator of mitochondrial membrane potential
摘要： The mitochondrial membrane potential (MMP) definitely reflects mitochondrial function. Thus, it is very essential to found a physical parameter as MMP indicator. At present, available parameters are either fluorescent intensity of monochromatic probes such as rhodamine 123 or a ratio of fluorescent intensity at different wavelengths of dual-color dyes such as JC-1, but the inconvenience in practice as well as serious effect of loading concentrations on experimental results limited their application. To address this concern, herein, we found a reliable and easily obtainable co-localization coefficient (CLC) of a fluorescent probe as new MMP indicator and developed a target switchable fluorescent probe (Mito-Lyso) to attain the aim. Due to intrinsic nature, Mito-Lyso exclusively stains mitochondria with normal MMP and a subsequent decreasing of MMP results in release of some Mito-Lyso. Importantly, the released Mito-Lyso can reversibly transfer between mitochondria and lysosomes. Thus, CLCs of Mito-Lyso and a commercial lysosomal probe (NIR-Lyso) can be MMP-dependent. CLCs gradually increased from 0.20 to 0.8 with the decreasing of MMP and then returned to 0.3 with the recovering of MMP, which better proves that the CLC is a valuable MMP indicator. Furthermore, both the design principle and action mechanism of Mito-Lyso has been explained in detail for the development of this type of probes.
关键词： Mito-Lyso,fluorescent probe,co-localization coefficient,mitochondrial membrane potential,target-switchable
更新于2025-09-04 15:30:14