scholarly journals Diode Laser Spectroscopy of the Dynamics of Multiphoton Excitation of SF6 Molecules by CO2 Laser Pulses

1988 ◽  
Vol 8 (2-4) ◽  
pp. 151-168 ◽  
Author(s):  
Yu. A. Kuritsyn ◽  
G. N. Makarov ◽  
I. Pak ◽  
M. V. Sotnikov ◽  
I. I. Zasavitsky ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Vibrational State ◽  
Rotational Quantum Number ◽  
Laser Pulses ◽  
Diode Laser Spectroscopy ◽  
Strong Disagreement ◽  
Theoretical Predictions ◽  
Excited Molecules ◽  
Theory And Experiments

The dynamics of excitation by CO2 laser pulses of SF6 molecules from individual rotational sublevels J″ of the ground vibrational state have been investigated in a pulsed molecular jet under essentially collisionless conditions. At different energy fluences of exciting laser pulse Φ = 10−5 + 10−1 J/cm2, the dependences of the fraction fJ of excited molecules on the rotational quantum number J″ have been obtained, when SF6 molecules were excited on the 10P(16) CO2 laser line, as well as on the 10P(18) and 10P(14) lines at Φ = 0.1 J/cm2. Comparison of experimental results with theoretical predictions18–20 shows rather strong disagreement between theory and experiments both in the population of the υ3 = 1 state and in the role of multiphoton transitions. It is shown that the narrowing of the exciting laser pulse spectrum (the 10P(16) line, Φ ≲ 10−2 J/cm2) results in drastic decrease of the fraction of excited molecules from the (υ3 = 0, J″ = 4) state which is most resonant with laser radiation.

scholarly journals High-intensity ultrashort laser-induced ablation of stainless steel foil targets in the presence of ambient gas

2003 ◽  
Vol 21 (1) ◽  
pp. 59-64 ◽  
Author(s):  
A. DI BERNARDO ◽  
C. COURTOIS ◽  
B. CROS ◽  
G. MATTHIEUSSENT ◽  
D. BATANI ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Atmospheric Pressure ◽  
Laser Pulses ◽  
Crater Formation ◽  
Stainless Steel Foil ◽  
Theoretical Predictions ◽  
Fs Laser ◽  
Ambient Gas ◽  
Ultrashort Laser

Ablation depths of stainless steel targets irradiated by 80-fs laser pulses at a flux F ≤ 40 J/cm2 (intensity ≤ 5 × 1014 W/cm2) in the presence of air at atmospheric pressure are experimentally measured. These values are lower than the theoretical predictions for metal targets in vacuum. Results are analyzed on the basis of the role of the ambient gas and of crater formation on the behavior of the ablated material.

A Laser Triggered Self-Sustaining Metals-Compound Semiconductor Transition for AlSb

1981 ◽  
Vol 4 ◽  
Author(s):  
R. Andrew ◽  
L. Baufay ◽  
A. Pigeolet ◽  
L.D. Laude
Keyword(s):  
Laser Pulse ◽  
Laser Annealing ◽  
Pulsed Laser ◽  
Laser Pulses ◽  
Pulsed Laser Annealing ◽  
Short Laser Pulses ◽  
Thermally Triggered ◽  
Heat Of Transformation ◽  
Complete Transformation

ABSTRACTThe preparation of AlSb thin films by pulsed laser annealing of Al/Sb sandwiches is studied in order to resolve some past controversy about the temperature rise induced by the laser pulse. Using 1000 Ȧ thick two layer films supported by TEM grids, we investigate the energy threshold for complete transformation as a function of pulse duration from 15 nsec to 100 msec, and of ambient temperature from −100°C to 250°C.We thence calculate the temperature effect directly induced by the laser to be about 930°C, or approximately the melting point of the metals, whereas inert gas furnace anneals of comparable films show transformation at this temperature occuring only in about 100 sec. We discuss the isoenergetic nature of the system for short laser pulses and the role of the heat of transformation, and thus conclude that the reaction is thermally triggered by the laser pulse but is to some extent self-sustaining via the heat of transformation locally distributed. This model is also shown to have equal validity for the systems CdTe, CdSe and AlAs.

scholarly journals Role of Laser Power, Wavelength, and Pulse Duration in Laser Assisted Tin-Induced Crystallization of Amorphous Silicon

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
V. B. Neimash ◽  
A. O. Goushcha ◽  
L. L. Fedorenko ◽  
P. Ye. Shepelyavyi ◽  
V. V. Strelchuk ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Amorphous Silicon ◽  
Temporal Distribution ◽  
Laser Pulses ◽  
Time Interval ◽  
Silicon Sample ◽  
Laser Pulse Intensity ◽  
Formation And Evolution ◽  
Induced Crystallization

This work describes tin-induced crystallization of amorphous silicon studied with Raman spectroscopy in thin-film structures Si-Sn-Si irradiated with pulsed laser light. We have found and analyzed dependencies of the nanocrystals’ size and concentration on the laser pulse intensity for 10 ns and 150 μm duration laser pulses at the wavelengths of 535 nm and 1070 nm. Efficient transformation of the amorphous silicon into a crystalline phase during the 10 ns time interval of the acting laser pulse in the 200 nm thickness films of the amorphous silicon was demonstrated. The results were analyzed theoretically by modeling the spatial and temporal distribution of temperature in the amorphous silicon sample within the laser spot location. Simulations confirmed importance of light absorption depth (irradiation wavelength) in formation and evolution of the temperature profile that affects the crystallization processes in irradiated structures.

An Experimental Investigation of Auditors' Liability: Implications for Social Welfare and Exploration of Deviations from Theoretical Predictions

2000 ◽  
Vol 75 (4) ◽  
pp. 429-451 ◽  
Author(s):  
Ronald R. King ◽  
Rachel Schwartz
Keyword(s):  
Experimental Investigation ◽  
Social Welfare ◽  
Strict Liability ◽  
Liability Rule ◽  
Optimal Response ◽  
Legal Regimes ◽  
Theoretical Predictions ◽  
Best Responses

This paper reports the results of an experiment designed to investigate how legal regimes affect social welfare. We investigate four legal regimes, each consisting of a liability rule (strict or negligence) and a damage measure (out-of-pocket or independent-of-investment). The results of the experiment are for the most part consistent with the qualitative predictions of Schwartz's (1997) model; however, subjects' actual choices deviate from the point predictions of the model. We explore whether these deviations arise because: (1) subjects form faulty anticipations of their counterparts' actions and/or (2) subjects do not choose the optimal responses given their anticipations. We find that subjects behave differently under the four regimes in terms of anticipation errors and departures from best responses. For example, subjects playing the role of auditors anticipate investments most accurately under the regime with strict liability combined with out-of-pocket damages, but are least likely to choose the optimal response given their anticipations. This finding implies that noneconomic factors likely play a role in determining subjects' choices.

scholarly journals Production of ion beams in high-power laser–plasma interactions and their applications

2004 ◽  
Vol 22 (1) ◽  
pp. 19-24 ◽  
Author(s):  
F. PEGORARO ◽  
S. ATZENI ◽  
M. BORGHESI ◽  
S. BULANOV ◽  
T. ESIRKEPOV ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Medical Physics ◽  
Ion Beam ◽  
Laser Pulses ◽  
Ion Beams ◽  
Laser Plasma Interactions ◽  
Physical Mechanisms ◽  
Short Laser Pulses ◽  
Laser Pulse Intensity ◽  
Target Design

Energetic ion beams are produced during the interaction of ultrahigh-intensity, short laser pulses with plasmas. These laser-produced ion beams have important applications ranging from the fast ignition of thermonuclear targets to proton imaging, deep proton lithography, medical physics, and injectors for conventional accelerators. Although the basic physical mechanisms of ion beam generation in the plasma produced by the laser pulse interaction with the target are common to all these applications, each application requires a specific optimization of the ion beam properties, that is, an appropriate choice of the target design and of the laser pulse intensity, shape, and duration.

scholarly journals A Stochastic Kinetic Type Reactions Model for COVID-19

Mathematics ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 1221
Author(s):  
Giorgio Sonnino ◽  
Fernando Mora ◽  
Pasquale Nardone
Keyword(s):  
Real Data ◽  
Stochastic Noise ◽  
Mathematical Basis ◽  
Sis Model ◽  
Theoretical Predictions ◽  
Coronavirus Infection ◽  
Massive Distribution ◽  
Second Wave ◽  
Stochastic Sis Model

We propose two stochastic models for the Coronavirus pandemic. The statistical properties of the models, in particular the correlation functions and the probability density functions, were duly computed. Our models take into account the adoption of lockdown measures as well as the crucial role of hospitals and health care institutes. To accomplish this work we adopt a kinetic-type reaction approach where the modelling of the lockdown measures is obtained by introducing a new mathematical basis and the intensity of the stochastic noise is derived by statistical mechanics. We analysed two scenarios: the stochastic SIS-model (Susceptible ⇒ Infectious ⇒ Susceptible) and the stochastic SIS-model integrated with the action of the hospitals; both models take into account the lockdown measures. We show that, for the case of the stochastic SIS-model, once the lockdown measures are removed, the Coronavirus infection will start growing again. However, the combined contributions of lockdown measures with the action of hospitals and health institutes is able to contain and even to dampen the spread of the SARS-CoV-2 epidemic. This result may be used during a period of time when the massive distribution of vaccines in a given population is not yet feasible. We analysed data for USA and France. In the case of USA, we analysed the following situations: USA is subjected to the first wave of infection by Coronavirus and USA is in the second wave of SARS-CoV-2 infection. The agreement between theoretical predictions and real data confirms the validity of our approach.

scholarly journals Electron Symmetry Breaking during Attosecond Charge Migration Induced by Laser Pulses: Point Group Analyses for Quantum Dynamics

Symmetry ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 205
Author(s):  
Dietrich Haase ◽  
Gunter Hermann ◽  
Jörn Manz ◽  
Vincent Pohl ◽  
Jean Christophe Tremblay
Keyword(s):  
Laser Pulse ◽  
Symmetry Breaking ◽  
Electric Fields ◽  
Quantum Dynamics ◽  
Point Group ◽  
Laser Pulses ◽  
Charge Migration ◽  
Laser Control ◽  
The One ◽  
Superposition States

Quantum simulations of the electron dynamics of oriented benzene and Mg-porphyrin driven by short (<10 fs) laser pulses yield electron symmetry breaking during attosecond charge migration. Nuclear motions are negligible on this time domain, i.e., the point group symmetries G = D6h and D4h of the nuclear scaffolds are conserved. At the same time, the symmetries of the one-electron densities are broken, however, to specific subgroups of G for the excited superposition states. These subgroups depend on the polarization and on the electric fields of the laser pulses. They can be determined either by inspection of the symmetry elements of the one-electron density which represents charge migration after the laser pulse, or by a new and more efficient group-theoretical approach. The results agree perfectly with each other. They suggest laser control of symmetry breaking. The choice of the target subgroup is restricted, however, by a new theorem, i.e., it must contain the symmetry group of the time-dependent electronic Hamiltonian of the oriented molecule interacting with the laser pulse(s). This theorem can also be applied to confirm or to falsify complementary suggestions of electron symmetry breaking by laser pulses.

scholarly journals Cylindrically and non-cylindrically symmetric expansion dynamics of tin microdroplets after ultrashort laser pulse impact

2021 ◽  
Vol 127 (2) ◽  
Author(s):  
Tiago de Faria Pinto ◽  
Jan Mathijssen ◽  
Randy Meijer ◽  
Hao Zhang ◽  
Alex Bayerle ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Laser Pulses ◽  
Femtosecond Laser Pulses ◽  
Droplet Deformation ◽  
Cylindrically Symmetric ◽  
Linearly Polarized ◽  
Particle Hydrodynamics ◽  
Deformation Dynamics ◽  
Smoothed Particle ◽  
Asymmetric Shock

AbstractIn this work, the expansion dynamics of liquid tin micro-droplets irradiated by femtosecond laser pulses were investigated. The effects of laser pulse duration, energy, and polarization on ablation, cavitation, and spallation dynamics were studied using laser pulse durations ranging from 220 fs to 10 ps, with energies ranging from 1 to 5 mJ, for micro-droplets with an initial radius of 15 and 23 $$\upmu$$ μ m. Using linearly polarized laser pulses, cylindrically asymmetric shock waves were produced, leading to novel non-symmetric target shapes, the asymmetry of which was studied as a function of laser pulse parameters and droplet size. A good qualitative agreement was obtained between smoothed-particle hydrodynamics simulations and high-resolution stroboscopic experimental data of the droplet deformation dynamics.

ENERGETIC PROTON ACCELERATION BY ULTRAINTENSE LASER PULSES IN INHOMOGENEOUS PLASMA TARGETS

2007 ◽  
Vol 21 (03n04) ◽  
pp. 642-646 ◽  
Author(s):  
A. ABUDUREXITI ◽  
Y. MIKADO ◽  
T. OKADA
Keyword(s):  
Laser Pulse ◽  
Inhomogeneous Plasma ◽  
Laser Pulses ◽  
Proton Acceleration ◽  
Particle In Cell ◽  
Target Plasma ◽  
Plasma Target ◽  
Experimental Process ◽  
Foil Target ◽  
Proton Bunch

Particle-in-Cell (PIC) simulations of fast particles produced by a short laser pulse with duration of 40 fs and an intensity of 1020W/cm2 interacting with a foil target are performed. The experimental process is numerically simulated by considering a triangular concave target illuminated by an ultraintense laser. We have demonstrated increased acceleration and higher proton energies for triangular concave targets. We also determined the optimum target plasma conditions for maximum proton acceleration. The results indicated that a change in the plasma target shape directly affects the degree of contraction accelerated proton bunch.

Ultrafast dynamic reflectivity of vanadium pentoxide

2008 ◽  
Vol 23 (2) ◽  
pp. 308-311 ◽  
Author(s):  
Gregory J. Taft ◽  
Matthew T. Newby ◽  
Joel J. Hrebik ◽  
Marshall Onellion ◽  
Thomas F. George ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Vanadium Pentoxide ◽  
Linear Polarization ◽  
Laser Pulses ◽  
Acoustic Vibrations ◽  
Frequency Oscillation ◽  
Ultrafast Dynamic ◽  
Transverse Acoustic ◽  
Wave Numbers ◽  
Lower Frequency Oscillation

The ultrafast dynamic reflectivity of vanadium pentoxide is measured using 40 fs pulses from a self-mode-locked Ti:sapphire laser. The laser pulses excite acoustic vibrations at wave numbers of 145 and 103 cm−1. The amplitudes of the induced oscillations depend strongly on the orientation between the linear polarization of the laser pulses and the crystal axes, with the largest oscillations observed for an orientation of 45°. The higher-frequency oscillation is induced immediately upon arrival of the laser pulse, while the lower-frequency oscillation appears a few picoseconds later. The oscillations persist for approximately 10 ps after the arrival of the pulse. The oscillations are attributed to transverse acoustic modes propagating along the a-axis of the crystal.

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