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Cluster-assisted generation of multicharged ions in nanosecond laser ionization of carbon bisulfide clusters at 1064nm
Xiao Xue,Li Hai-Yang,Niu Dong-Mei,Luo Xiao-Lin,
肖 雪

中国物理 B , 2007,
Abstract: The photoionization of seeded carbon bisulfide molecular beam by a 1064\,nm nanosecond Nd-YAG laser with intensities varying from $0.8\times10^{11}$ to $5.6\times10^{11}$\,W/cm$^{2}$ have been studied by time-of-flight mass spectrometry. Multiply charged ions of S$^{q + }$ ($q$ = 2--6) and C$^{q +}$ ($q$ = 2--4) with kinetic energy of hundreds of electron volts have been observed, and there are strong experimental evidences indicating that those multicharged ions originate from the ionization of CS$_{2}$ neat clusters in the beam. An electron recolliding ionization model is proposed to explain the appearance of those multiply charged atomic ions under such low laser intensities.
To the electrostrictive mechanism of nanosecond-pulsed breakdown in liquid phase  [PDF]
Yohan Seepersad,Danil Dobrynin,Mikhail Pekker,Mikhail N. Shneider,Alexander Fridman
Physics , 2013, DOI: 10.1088/0022-3727/46/16/162001
Abstract: In this study we have studied the initial stage of the nanosecond-pulsed discharge development in liquid phase. Modeling predicts that in the case of fast rising strong nonhomogeneous electric fields in the vicinity of high voltage pin electrode a region saturated with nanoscale non-uniformities may be developed. This phenomenon is attributed to the electrostriction mechanisms and may be used to explain development of breakdown in liquid phase. In this work, schlieren method was used in order to demonstrate formation of negative pressure region in liquids with different dielectric permittivity constants: water, ethanol and ethanol-water mixture. It is shown that this density perturbation, formed at the raising edge of the high voltage pulse, is followed by a generation of a shock wave propagating with the speed of sound away from the electrode, with negative pressure behind it.
Accessing defect dynamics using intense, nanosecond pulsed ion beams  [PDF]
A. Persaud,J. J. Barnard,H. Guo,P. Hosemann,S. Lidia,A. M. Minor,P. A. Seidl,T. Schenkel
Physics , 2014,
Abstract: Gaining in-situ access to relaxation dynamics of radiation induced defects will lead to a better understanding of materials and is important for the verification of theoretical models and simulations. We show preliminary results from experiments at the new Neutralized Drift Compression Experiment (NDCX-II) at Lawrence Berkeley National Laboratory that will enable in-situ access to defect dynamics through pump-probe experiments. Here, the unique capabilities of the NDCX-II accelerator to generate intense, nanosecond pulsed ion beams are utilized. Preliminary data of channeling experiments using lithium and potassium ions and silicon membranes are shown. We compare these data to simulation results using Crystal Trim. Furthermore, we discuss the improvements to the accelerator to higher performance levels and the new diagnostics tools that are being incorporated.
Analysis of Flashover Characteristics under Nanosecond Pulsed Coaxial Electric Field  [PDF]
W. L. Huang, J. F. Cui, G. S. Sun
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2009, DOI: 10.4236/jemaa.2009.12015
Abstract: Under nanosecond pulsed coaxial electric field, surface flashover voltage over the interfaces between nylon 1010 and transformer oil increases almost linearly with gap length, and the steeper rising edge of applied pulse, the higher flash-over voltage. Surface flashover properties are closely related to the electric field at the triple junctions of solid-liquid-electrode and the field gradient along the interfaces. Although the increased difference between inner and outer electrode radii will enhance electric field strength at the triple junctions and nonuniformity degree of potential distribution along interfaces, it reduces simultaneously terribly the surface field strength of coaxial inner electrode, so that flashover voltage doesn’t descend, but ascends almost linearly with gap length. The average flashover strength in coaxial electric field can be estimated by that in uniform electric field for large enough difference between inner and outer electrode radii, which is useful to practical engineering design for coaxial pulsed power apparatuses.
Optical Limiting and Stabilization Properties of a Liquid Dye on 1064 nm Nanosecond Laser Pulses  [PDF]
Liuheng Wang, Rongzong Peng, Yuxia Zhao, Feipeng Wu
Optics and Photonics Journal (OPJ) , 2013, DOI: 10.4236/opj.2013.32B008

A novel liquid dye 2-((2E,5E)-2,5-bis(4-(methyl(2,5, 8,11-tetraoxatridecan-13-yl)amino)benzylidene)cyclopentylidene) malononitrile (TO-BDCM) was synthesized by incorporating two oligo(ethenyl glycol) groups into the backbone of a prototype malononitrile derivative (BDCM) for the purpose of increasing its solubility in organic solvents. The nonlinear absorption properties of this liquid dye on 1064 nm ns pulsed laser were investigated in DMF with remarkably high concentration up to ~1M, showing a superior large nonlinear absorption coefficient of 55.6 cm3/GW2. Fairly good optical limiting and stabilization effects were achieved. Meanwhile, the liquid dye exhibited equivalent stability under laser irradiation compared to its prototype dye BDCM.

Two Modes of Cell Death Caused by Exposure to Nanosecond Pulsed Electric Field  [PDF]
Olga N. Pakhomova, Betsy W. Gregory, Iurii Semenov, Andrei G. Pakhomov
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0070278
Abstract: High-amplitude electric pulses of nanosecond duration, also known as nanosecond pulsed electric field (nsPEF), are a novel modality with promising applications for cell stimulation and tissue ablation. However, key mechanisms responsible for the cytotoxicity of nsPEF have not been established. We show that the principal cause of cell death induced by 60- or 300-ns pulses in U937 cells is the loss of the plasma membrane integrity (“nanoelectroporation”), leading to water uptake, cell swelling, and eventual membrane rupture. Most of this early necrotic death occurs within 1–2 hr after nsPEF exposure. The uptake of water is driven by the presence of pore-impermeable solutes inside the cell, and can be counterbalanced by the presence of a pore-impermeable solute such as sucrose in the medium. Sucrose blocks swelling and prevents the early necrotic death; however the long-term cell survival (24 and 48 hr) does not significantly change. Cells protected with sucrose demonstrate higher incidence of the delayed death (6–24 hr post nsPEF). These cells are more often positive for the uptake of an early apoptotic marker dye YO-PRO-1 while remaining impermeable to propidium iodide. Instead of swelling, these cells often develop apoptotic fragmentation of the cytoplasm. Caspase 3/7 activity increases already in 1 hr after nsPEF and poly-ADP ribose polymerase (PARP) cleavage is detected in 2 hr. Staurosporin-treated positive control cells develop these apoptotic signs only in 3 and 4 hr, respectively. We conclude that nsPEF exposure triggers both necrotic and apoptotic pathways. The early necrotic death prevails under standard cell culture conditions, but cells rescued from the necrosis nonetheless die later on by apoptosis. The balance between the two modes of cell death can be controlled by enabling or blocking cell swelling.
Transient Features in Nanosecond Pulsed Electric Fields Differentially Modulate Mitochondria and Viability  [PDF]
Stephen J. Beebe, Yeong-Jer Chen, Nova M. Sain, Karl H. Schoenbach, Shu Xiao
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0051349
Abstract: It is hypothesized that high frequency components of nanosecond pulsed electric fields (nsPEFs), determined by transient pulse features, are important for maximizing electric field interactions with intracellular structures. For monopolar square wave pulses, these transient features are determined by the rapid rise and fall of the pulsed electric fields. To determine effects on mitochondria membranes and plasma membranes, N1-S1 hepatocellular carcinoma cells were exposed to single 600 ns pulses with varying electric fields (0–80 kV/cm) and short (15 ns) or long (150 ns) rise and fall times. Plasma membrane effects were evaluated using Fluo-4 to determine calcium influx, the only measurable source of increases in intracellular calcium. Mitochondria membrane effects were evaluated using tetramethylrhodamine ethyl ester (TMRE) to determine mitochondria membrane potentials (ΔΨm). Single pulses with short rise and fall times caused electric field-dependent increases in calcium influx, dissipation of ΔΨm and cell death. Pulses with long rise and fall times exhibited electric field-dependent increases in calcium influx, but diminished effects on dissipation of ΔΨm and viability. Results indicate that high frequency components have significant differential impact on mitochondria membranes, which determines cell death, but lesser variances on plasma membranes, which allows calcium influxes, a primary determinant for dissipation of ΔΨm and cell death.
Induction of Cell Death Mechanisms and Apoptosis by Nanosecond Pulsed Electric Fields (nsPEFs)  [PDF]
Stephen J. Beebe,Nova M. Sain,Wei Ren
Cells , 2013, DOI: 10.3390/cells2010136
Abstract: Pulse power technology using nanosecond pulsed electric fields (nsPEFs) offers a new stimulus to modulate cell functions or induce cell death for cancer cell ablation . New data and a literature review demonstrate fundamental and basic cellular mechanisms when nsPEFs interact with cellular targets. NsPEFs supra-electroporate cells creating large numbers of nanopores in all cell membranes. While nsPEFs have multiple cellular targets, these studies show that nsPEF-induced dissipation of ΔΨm closely parallels deterioration in cell viability. Increases in intracellular Ca 2+ alone were not sufficient for cell death; however, cell death depended of the presence of Ca 2+. When both events occur, cell death ensues. Further, direct evidence supports the hypothesis that pulse rise-fall times or high frequency components of nsPEFs are important for decreasing ΔΨm and cell viability. Evidence indicates in Jurkat cells that cytochrome c release from mitochondria is caspase-independent indicating an absence of extrinsic apoptosis and that cell death can be caspase-dependent and –independent. The Ca 2+ dependence of nsPEF-induced dissipation of ΔΨm suggests that nanoporation of inner mitochondria membranes is less likely and effects on a Ca 2+-dependent protein(s) or the membrane in which it is embedded are more likely a target for nsPEF-induced cell death. The mitochondria permeability transition pore (mPTP) complex is a likely candidate. Data demonstrate that nsPEFs can bypass cancer mutations that evade apoptosis through mechanisms at either the DISC or the apoptosome.
Pulsed 1064 nm Nd-YAG Laser Deposition of Titanium on Silicon in a Nitrogen Environment  [cached]
Jose Omar Amistoso,Edgardo Pabit,Marilyn Hui,Wilson Garcia
Science Diliman , 1999,
Abstract: Pulsed laser deposition (PLD) technique was demonstrated for the deposition of titanium nitride (TiN) thin films on Si (100) substrates. A 1064 nm pulsed Nd-YAG laser is focused on a titanium (99.5%) target in a nitrogen environment to generate the atomic flux needed for the film deposition. Spectroscopic analysis of the plasma emission indicates the presence of atomic titanium and nitrogen, which are the precursors of TiN. Images of the films grown at different laser pulse energies show an increase in the number and size of deposited droplets and clusters with increasing laser pulse energy. A decrease in cluster and droplet size is also observed, with an increase in substrate temperature. EDS data show an increase in the titanium peak relative to the silicon as the ambient nitrogen pressure is decreased. An increase in deposition time was found to result in large clusters and irregularly shaped structures on the substrate. Post-deposition annealing of the samples enhanced the crystallinity of the film.
Comparative Study of the Dissociative Ionization of 1,1,1 Trichloroethane Using Nanosecond and Femtosecond Laser Pulses  [PDF]
Anton Du Plessis,Christien Strydom,Lourens Botha
International Journal of Molecular Sciences , 2010, DOI: 10.3390/ijms11031114
Abstract: Changes in the laser induced molecular dissociation of 1,1,1-trichloroethane (TCE) were studied using a range of intensities and standard laser wavelengths with nanosecond and femtosecond pulse durations. TCE contains C-H, C-C and C-Cl bonds and selective bond breakage of one or more of these bonds is of scientific interest. Using laser ionization time of flight mass spectrometry, it was found that considerable variation of fragment ion peak heights as well as changes in relative peak ratios is possible by varying the laser intensity (by attenuation), wavelength and pulse duration using standard laser sources. The nanosecond laser dissociation seems to occur via C-Cl bond breakage, with significant fragmentation and only a few large mass ion peaks observed. In contrast, femtosecond laser dissociative ionization results in many large mass ion peaks. Evidence is found for various competing dissociation and ionization pathways. Variation of the nanosecond laser intensity does not change the fragmentation pattern, while at high femtosecond intensities large changes are observed in relative ion peak sizes. The total ionization yield and fragmentation ratios are presented for a range of wavelengths and intensities, and compared to the changes observed due to a linear chirp variation.
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