scholarly journals Wavelength scaling of electron collision time in plasma for strong field laser-matter interactions in solids

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Garima C. Nagar ◽  
Dennis Dempsey ◽  
Bonggu Shim
Keyword(s):  
Dielectric Constant ◽  
Plasma Density ◽  
Strong Field ◽  
Experimental Studies ◽  
Wavelength Dependence ◽  
Light Diffraction ◽  
Electron Collision ◽  
Collision Time ◽  
Time Resolved ◽  
Laser Filamentation

AbstractAlthough the dielectric constant of plasma depends on electron collision time as well as wavelength and plasma density, experimental studies on the electron collision time and its effects on laser-matter interactions are lacking. Here, we report an anomalous regime of laser-matter interactions generated by wavelength dependence (1.2–2.3 µm) of the electron collision time in plasma for laser filamentation in solids. Our experiments using time-resolved interferometry reveal that electron collision times are small (<1 femtosecond) and decrease as the driver wavelength increases, which creates a previously-unobserved regime of light defocusing in plasma: longer wavelengths have less plasma defocusing. This anomalous plasma defocusing is counterbalanced by light diffraction which is greater at longer wavelengths, resulting in almost constant plasma densities with wavelength. Our wavelength-scaled study suggests that both the plasma density and electron collision time should be systematically investigated for a better understanding of strong field laser-matter interactions in solids.

THEORETICAL STUDIES OF TRANSIENT RAMAN SCATTERING OF NON-EQUILIBRIUM CARRIERS IN SEMICONDUCTORS — EFFECTS OF CARRIER COLLISIONS

1993 ◽  
Vol 07 (06) ◽  
pp. 331-353 ◽  
Author(s):  
C. CHIA ◽  
OTTO F. SANKEY ◽  
K. T. TSEN
Keyword(s):  
Raman Scattering ◽  
Optical Transition ◽  
Density Fluctuations ◽  
Collision Time ◽  
Time Resolved ◽  
Comprehensive Theory ◽  
Scattering Spectrum ◽  
Bandgap Semiconductors ◽  
Ultrashort Laser ◽  
Non Equilibrium

We present a comprehensive theory for time-resolved Raman scattering from non-equilibrium electrons in direct bandgap semiconductors. Specifically, we include (1) the effects of probing with ultrashort laser pulse: (2) the effects of finite carrier collision time; (3) the effects of band structure; and (4) the effects of damping in the optical transition, in the calculations of Raman scattering cross section. Both elastic and inelastic scattering processes are taken into account in formulating the effects of carrier collision time. The effects of damping in the optical transitions have to be considered for the experimental condition of probing with above-bandgap laser excitations even if under some circumstances they do not drastically change the lineshape of the single-particle-scattering spectrum due to spin-density fluctuations.

Microwave and Electrical Properties of Zr-Doped SrTiO3 for Dielectric Resonator Antenna Application

2018 ◽  
Vol 280 ◽  
pp. 142-148 ◽  
Author(s):  
Norhizatol Fashren Muhamad ◽  
Rozana Aina Maulat Osman ◽  
Mohd Sobri Idris ◽  
Faizal Jamlos ◽  
Nor Azura Malini Ahmad Hambali
Keyword(s):  
Dielectric Constant ◽  
Electrical Properties ◽  
Dielectric Loss ◽  
Dielectric Resonator ◽  
Ceramic Powder ◽  
Experimental Studies ◽  
Orthorhombic Phase ◽  
Solid State Reaction Method ◽  
Dielectric Resonator Antenna ◽  
Conventional Solid State Reaction

Present investigation provides experimental studies on cylindrical dielectric resonator antennas (CDRAs) fabricated from SrTi1-xZrxO3ceramic with different substitution of Zr in place of Ti for (0 ≤ x ≤1). Ceramic powder were prepared using conventional solid state reaction method. X-ray Diffraction exposes physical properties Zr-doped SrTiO3which exhibit phase transition from cubic, tetragonal to orthorhombic phase. The electrical properties such as dielectric constant (εr) and dielectric loss (tan δ) were studied in variation of temperatures and frequencies. At room temperature the dielectric constant decreased from 240 to 21 with increase of Zr content however the amazing result was obtained for multiband antenna by Zr content. The dielectric loss obtain shows very low loss value roughly below 0.07 for all samples. The variations of return loss, resonance frequency and bandwidth of CDRAs at their respective resonant frequencies are studied experimentally.

Turbulence Characteristics in a Rushton Stirring Vessel Measured via Time Resolved DPIV

2006 ◽  
Author(s):  
Michael R. Brady ◽  
Demetri P. Telionis ◽  
Pavlos P. Vlachos
Keyword(s):  
Experimental Studies ◽  
Turbulent Energy ◽  
Industrial Applications ◽  
Solid Particles ◽  
Analytical Models ◽  
Frequency Resolution ◽  
Time Resolved ◽  
Turbulence Characteristics ◽  
Stirred Vessels ◽  
Rushton Impeller

Stirred vessels are devices that find extensive industrial applications particularly in mineral and chemical industries. Interactions of solid particles and/or bubbles and particles depend on the characteristics of turbulent flow. In many analytical models, the rate of collision is a function of turbulence dissipation. It has been known that dissipation levels are much higher in the neighborhood of the agitating mechanism, in our case the Rushton impeller. In this paper we use time-resolved DPIV to measure the velocity field with a spatial resolution down to 100 μm, and a frequency resolution of 500 Hz. The range of Reynolds numbers investigated varied from 20,000 to 50,000, with the smallest Kolmogorov length scale of about 15 μm. The flow in the impeller stream of a Rushton impeller can be best summarized as a radial jet with a pair of convecting tip vortices. The turbulence quantities were found by removing the periodic component from the blade passing, which is the dominant part of the measured velocities. Dissipation was calculated from the velocity gradients, and assuming isotropy. We provide further evidence that larger dissipation values in the vicinity of the impeller are consistent with the dynamic motion generated by the blade passage. This is somewhat anti-intuitive, because energy is dissipated at the smallest eddy scales, and the immediate vicinity of the impeller contains large vortical structures and provides little space or time for such structures to break down. The maximum and mean normalized dissipation in the impeller stream showed decreasing trends with the Reynolds number. Other normalized turbulence quantities, namely Vrms and in plane vorticity are presented. Our experiments agree very well with other experimental studies. Estimates of turbulence characteristics and in particular distributions of turbulent energy dissipation determined in this study will be used in estimating rates of collisions of bubbles and particles in stirred vessels.

Prompt Transient Heat Transfer Effects in Low-Fluence Laser Induced Incandescence

2012 ◽  
Author(s):  
F. Memarian ◽  
K. J. Daun
Keyword(s):  
Experimental Studies ◽  
Direct Simulation Monte Carlo ◽  
Recent Time ◽  
Direct Simulation ◽  
Transient Effects ◽  
Time Resolved ◽  
Laser Induced Incandescence ◽  
Simulation Monte Carlo ◽  
Heat Transfer Effects ◽  
Particle Cooling

Recent time-resolved laser-induced incandescence (TiRe-LII) experimental studies have revealed anomalies in particle cooling rates that cannot be explained using steady-state conduction models. This is the first study to use Direct Simulation Monte Carlo (DSMC) to investigate possible transient effects in heat conduction between the laser-energized particle and surrounding gas. While the DSMC results reveal an increased cooling rate shortly after the laser pulse, this effect is small relative to experimentally-observed anomalous cooling.

Time-Resolved Velocity Measurements in a Matched Refractive Index Facility of Randomly Packed Spheres

2018 ◽  
Author(s):  
Ethan Kappes ◽  
Mateusz Marciniak ◽  
Andrew Mills ◽  
Robert Muyshondt ◽  
Stephen King ◽  
...  
Keyword(s):  
Root Mean Square ◽  
Experimental Studies ◽  
Reynolds Numbers ◽  
Index Of Refraction ◽  
Mean Square ◽  
Reynolds Stresses ◽  
Velocity Measurements ◽  
Mean Velocity ◽  
Time Resolved ◽  
Wall Boundary

Complex geometries and randomly connected void spaces within packed beds have hindered efforts to characterize the underlying transport phenomena occurring within. In this communication, we present our experimental studies on a facility of randomly packed spheres that can be a representative of sections within a reactor core in a nuclear power plant. The results of high-fidelity velocity measurements can be seen using Time-Resolved Particle Image Velocimetry (TR-PIV) at the pore scales and near the wall boundary in the Matched Index of Refraction (MIR) facility. The MIR approach allows for a non-invasive analysis of the flow within packed spheres at the microscopic scales with high temporal and spatial resolution. Flow characteristics obtained from the TR-PIV measurements at various Reynolds numbers are presented. The results include the first- and second-order flow statistics, such as mean velocity, root-mean-square fluctuating velocity and Reynolds stresses. Effects of the wall boundary and Reynolds numbers on flow patterns are currently being investigated. Comparisons of the mean velocities, root-mean-square fluctuating velocities, and Reynolds stress components show the increase of flow mixing and turbulent intensities within the gaps between spheres in the packed bed. Sizes of recirculation regions, however, seem to be independent of the increase of Reynolds numbers.

scholarly journals Tracking dissociation dynamics of strong-field ionized 1,2-dibromoethane with femtosecond XUV transient absorption spectroscopy

2016 ◽  
Vol 18 (21) ◽  
pp. 14644-14653 ◽  
Author(s):  
Adam S. Chatterley ◽  
Florian Lackner ◽  
Daniel M. Neumark ◽  
Stephen R. Leone ◽  
Oliver Gessner
Keyword(s):  
Absorption Spectroscopy ◽  
Near Infrared ◽  
Transient Absorption ◽  
Extreme Ultraviolet ◽  
Strong Field ◽  
Transient Absorption Spectroscopy ◽  
Time Resolved ◽  
Strong Field Ionization ◽  
Dissociation Dynamics ◽  
Ultraviolet Absorption Spectroscopy

Using femtosecond time-resolved extreme ultraviolet absorption spectroscopy, the dissociation dynamics of the haloalkane 1,2-dibromoethane (DBE) have been explored following strong field ionization by femtosecond near infrared pulses at intensities between 7.5 × 1013 and 2.2 × 1014 W cm−2.

scholarly journals Pump- And Probe-Wavelength Dependencies of Picosecond Anti-Stokes Raman Spectrum of Trans-Stilbene in the S1 State

1999 ◽  
Vol 19 (1-4) ◽  
pp. 75-78 ◽  
Author(s):  
Takakazu Nakabayashi ◽  
Hiromi Okamoto ◽  
Mitsuo Tasumi
Keyword(s):  
Vibrational Relaxation ◽  
Vibrational Energy ◽  
Wavelength Dependence ◽  
Relaxation Dynamics ◽  
Vibrationally Excited ◽  
Time Resolved ◽  
Probe Wavelength ◽  
Trans Stilbene ◽  
Pump And Probe ◽  
Anti Stokes

Vibrational relaxation dynamics of trans-stilbene in the S1 state immediately after photoexcitation is studied by picosecond time-resolved anti-Stokes Raman spectroscopy with several pump and probe wavelengths. Pump-wavelength dependence of the anti- Stokes spectrum indicates that, when pump photons with high excess energy (≈5200cm-1) are used, the anti-Stokes Raman bands at 0 ps delay time arise from vibrationally excited transients with excess vibrational energy not thermally distributed in the molecule. Probe-wavelength dependence suggests that the vibrationally excited transients at 0 ps are mostly on the lowest excited vibrational levels, as far as the olefinic C═C stretching and the C–Ph stretching modes are concerned. The vibrational relaxation process of S1trans-stilbene is discussed on the basis of the observed results.

Soft-Mode Phonons in SrTiO3 Thin Films Studied by Far-Infrared Ellipsometry and Raman Scattering

1999 ◽  
Vol 603 ◽  
Author(s):  
A. A. Sirenko ◽  
C. Bernhard ◽  
A. Golnik ◽  
I. A. Akimov ◽  
A. M. Clark ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Raman Scattering ◽  
Soft Mode ◽  
Experimental Studies ◽  
Low Frequency ◽  
Pulsed Laser ◽  
Far Infrared ◽  
Laser Deposition ◽  
Bulk Crystals ◽  
Infrared Ellipsometry

AbstractWe report the experimental studies of the vibrational spectra of SrTiO3 films with the thickness of 1 µm grown by pulsed laser deposition. Fourier-transform infrared ellipsometry between 30 and 700 cm−1 and electric field-induced Raman scattering have been utilized for investigation of the phonon behavior. These results can be used for comparison with the low-frequency measurements of the static dielectric constant. In the films, the soft mode reveals hardening compared to that in bulk crystals. This observation is in agreement with the Lyddane-Sachs-Teller formalism.

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