574 research outputs found
Threshold Laws for the Break-up of Atomic Particles into Several Charged Fragments
The processes with three or more charged particles in the final state exhibit
particular threshold behavior, as inferred by the famous Wannier law for (2e +
ion) system. We formulate a general solution which determines the threshold
behavior of the cross section for multiple fragmentation. Applications to
several systems of particular importance with three, four and five leptons
(electrons and positrons) in the field of charged core; and two pairs of
identical particles with opposite charges are presented. New threshold
exponents for these systems are predicted, while some previously suggested
threshold laws are revised.Comment: 40 pages, Revtex, scheduled for the July issue of Phys.Rev.A (1998
Theoretical study of ionization of an alkali atom adsorbed on a metal surface by laser assisted subfemtosecond pulse
The first numerical simulation of the process of ionization of an atom
adsorbed on a metal surface by the subfemtosecond pulse is presented. The
streaking scheme is considered, when a weak sub-femtosecond pulse comes
together with a strong IR pulse with a variable delay between them. The problem
is analyzed with numerical solving the non-stationary Schroedinger equation in
the cylindrical coordinate. The results obtained are compared with ones in the
gas phase. We show that the surface influences the DDCS, but the observation of
this influence, beside the trivial polarization shift of the energy of the
initial state, requires a quite high experimental resolution
Ultrafast Laser Nanostructured ITO Acts as Liquid Crystal Alignment Layer and Higher Transparency Electrode
Electrodes with higher transparency that can also align liquid crystals (LCs)
are of high importance for improved costs and energy consumption of LC
displays. Here we demonstrate for the first time alignment of liquid crystals
on femtosecond laser nanostructured indium tin oxide (ITO) coated glass
exhibiting also higher transparency due to the less interface reflections. The
nano paterns were created by fs laser directlly on ITO films without any
additional spin coating materials or lithography procces. Nine regions of
laser-induced nanostructures were fabricated with different alignment
orientations and various pulse energy levels on top of the ITO. The device
interfacial anchoring energy was found to be comparable to the anchoring energy
of nematic LC on photosensitive polymers. The device exhibits contrast of 30:1
and relaxation time of 330ms expected for thick LC devices. The measured
transparency of the LC device with two ITO nanograting substrates is 10% higher
than the uniform ITO film based LC devices. The alignment methodology presented
here paves the way for improved LC displays and new structured LC photonic
devices
Femtosecond laser nanostructuring of transparent materials: from bulk to fiber lasers
Progress in high power ultra-short pulse lasers has opened new frontiers in the physics of light-matter interactions and laser material processing. Recently there has been considerable interest in the application of femtosecond lasers to writing inside transparent materials and in particular to fabrication of three-dimensional microstructures
Self-assembled nanostructuring of a-Si:H films with ultrashort light pulses
For several decades, hydrogenated amorphous silicon (a-Si:H) has been playing a significant role in the world's production of photovoltaic modules. In this work, we investigate different types of modifications induced by a femtosecond laser in a-Si:H thin films. We demonstrate that several distinctive modification regimes with peculiar optical properties can be obtained in a narrow range of the laser pulse energies
SnO<sub>2</sub> nanoparticles in silica: nanosized tools for femtosecond-laser machining of refractive index patterns
We show that SnO2 nanoclusters in silica interact with ultrashort infrared laser pulses focused inside the material generating a hydrostatic compression and photoelastic response of the surrounding glass. This effect, together with the laser-induced nanocluster amorphization, gives rise to positive or negative refractive-index changes, up to 10ā2, depending on the beam-power density. This result points out a wide tuning of the refractive index patterns obtainable in silica-based optical technology
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