Effect of laser pulse time profile on its absorption by argon clusters

Mishra, Gauravi; Holkundkar, Amol R.; Gupta, Nidhi

doi:10.1017/s0263034611000346

Cited by 11 publications

(10 citation statements)

References 40 publications

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“…MD codes in Refs. [47][48][49][50][51][52][53] have reported similar kind of r 0 values as in Refs. [43][44][45].…”

Section: A Details Of Molecular Dynamics Simulationsupporting

confidence: 78%

“…The code is validated by verifying the energy conservation of the system as well as identifying the electron plasma oscillation with desired Mie-plasma frequency ω M for the spherical cluster plasma. Although there are plenty of MD simulations for clusters [2,30,41,[43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58], verification of this natural oscillation through MD simulation is rarely reported which is extremely important, particularly to study frequency dependent phenomena, e.g., anharmonic and harmonic resonance absorption in laser driven plasmas. Otherwise, resonance physics may be missing in simulations and subsequent MD results could be misleading.…”

Section: A Details Of Molecular Dynamics Simulationmentioning

confidence: 99%

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Anharmonic resonance absorption of short laser pulses in clusters: A molecular dynamics simulation study

Mahalik

Kundu

2016

Physics of Plasmas

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Linear resonance (LR) absorption of an intense 800 nm laser light in a nano-cluster requires a long laser pulse > 100 fs when Mie-plasma frequency (ω M ) of electrons in the expanding cluster matches the laser frequency (ω). For a short duration of the pulse the condition for LR is not satisfied. In this case, it was shown by a model and particle-in-cell (PIC) simulations [Phys. Rev. Lett. 96, 123401 (2006)] that electrons absorb laser energy by anharmonic resonance (AHR) when the position-dependent frequency Ω[r(t)] of an electron in the selfconsistent anharmonic potential of the cluster satisfies Ω[r(t)] = ω. However, AHR remains to be a debate and still obscure in multi-particle plasma simulations. Here, we identify AHR mechanism in a laser driven cluster using molecular dynamics (MD) simulations. By analyzing the trajectory of each MD electron and extracting its Ω[r(t)] in the self-generated anharmonic plasma potential it is found that electron is outer ionized only when AHR is met. An anharmonic oscillator model, introduced here, brings out most of the features of MD electrons while passing the AHR. Thus, we not only bridge the gap between PIC simulations, analytical models and MD calculations for the first time but also unequivocally prove that AHR processes is a universal dominant collisionless mechanism of absorption in the short pulse regime or in the early time of longer pulses in clusters.

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“…MD codes in Refs. [47][48][49][50][51][52][53] have reported similar kind of r 0 values as in Refs. [43][44][45].…”

Section: A Details Of Molecular Dynamics Simulationsupporting

confidence: 78%

Section: A Details Of Molecular Dynamics Simulationmentioning

confidence: 99%

Anharmonic resonance absorption of short laser pulses in clusters: A molecular dynamics simulation study

Mahalik

Kundu

2016

Physics of Plasmas

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“…14,15 The population of atoms inside the cluster is obtained from initial radius (R 0 ) and Wigner-Seitz radius (R W ) as, N Atoms ¼ ðR 0 =R W Þ 3 . The value of R W is specific to cluster type under study, e.g., it is 1.70, 2.02, 2.40, and 2.73 Å for deuterium, neon, argon, and xenon clusters, respectively.…”

Section: Numerical Modelmentioning

confidence: 99%

Molecular dynamic studies on anisotropic explosion of laser irradiated Xe cluster

Mishra

Gupta

2012

Physics of Plasmas

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A three dimensional molecular dynamic model is used to investigate the dynamics of Xe clusters of various radii irradiated by laser of moderate intensities ($10 14 À10 16 W=cm 2 ). The FWHM pulse duration of the laser is varied from few laser cycles to hundreds of femtosecond. For cluster of radius 50 Å irradiated by a laser of 170 fs pulse duration, it is observed that ion yield is more along the direction of laser polarization than perpendicular to it. This trend reverses (more ions are emitted along the direction perpendicular to laser polarization than parallel to it) when laser pulses of few cycles are used. This reversal of anisotropy is explained on the basis of spatial shielding of ions due to the oscillating inner electron cloud along direction of laser electric field. The nature of anisotropy remains same with variations in laser intensity and cluster size. V C 2012 American Institute of Physics. [http://dx.

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“…In fact, historic experiment 13 claiming multi-keV electron energy and its double peak spectrum were later called into question 14 , 40 ; but values of in those cases were found about times the electron’s ponderomotive energy (the average energy of a free electron in an oscillating field ). Similarly, various oscillator models 24 , 31 – 34 , 37 , 41 , MD and PIC simulations 33 , 34 , 37 , 41 , 42 , 45 – 49 showed near . Thus our extensive survey (see Table 1 ) reveals that in the collisionless regime of LCI, value of mostly remains close to the famous of the laser-atom interaction 50 – 52 ; except in a few cases 43 , 44 , 53 where electron’s energy around (or more) were also reported which is imprecise to us.…”

Section: Introductionmentioning

confidence: 76%

Laser cluster interaction in ambient magnetic fields for accelerating electrons in two stages without external injection

Kalyani

Mahalik

Kundu

2022

Sci Rep

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In the few-cycle pulse regime of laser-cluster interaction (intensity $$>10^{16}\,\text{ W/cm}^{2}$$ > 10 16 W/cm 2 , wavelength $$> 780$$ > 780 nm), laser absorption is mostly collisionless and may happen via anharmonic resonance (AHR) process in the overdense (cluster) plasma potential. Many experiments, theory and simulation show average absorbed energy per cluster-electron ($${\mathcal {E}_A}$$ E A ) close to the electron’s ponderomotive energy ($$U_\mathrm {p}$$ U p ) in the collisionless regime. In this work, by simple rigid sphere model (RSM) and detailed particle-in-cell (PIC) simulation, we show enhanced $${\mathcal {E}_A}\approx$$ E A ≈ 30–70$$U_\mathrm {p}$$ U p —a 15–30 fold increase—with an external (crossed) magnetic field near the electron-cyclotron resonance (ECR). Due to relativistic mass increase, electrons quickly deviate from the standard (non-relativistic) ECR, but time-dependent relativistic-ECR (RECR) happens which also contributes to enhanced $${\mathcal {E}_A}$$ E A . Here laser is coupled to electrons in two stages, i.e, AHR and ECR/RECR. To probe further we retrieve the phase-difference $$\Delta \psi$$ Δ ψ between the driving electric field and corresponding velocity component for each electron (in PIC and RSM). We find absorption by electron via AHR happens in a very short interval $$\Delta \tau$$ Δ τ for less than half a laser period where $$\Delta \psi$$ Δ ψ remains close to $$\pi$$ π (necessary condition for maximum laser absorption) and then $$\Delta \psi$$ Δ ψ drops to its initial $$\pi /2$$ π / 2 (meaning no absorption) after such short-lived AHR. On the contrary, auxiliary magnetic field near the ECR modifies AHR scenario inside the cluster and also helps maintaining the required phase $$\Delta \psi \approx \pi$$ Δ ψ ≈ π for the liberated cluster-electron accompanied by frequency matching for ECR/RECR for a prolonged $$\Delta \tau$$ Δ τ (which covers 50–60% of the laser pulse through pulse maxima) even after AHR—leading to jump in $${\mathcal {E}_A}\approx$$ E A ≈ 30–70$$U_\mathrm {p}$$ U p . We note that to realize the second stage of enhanced energy coupling via ECR/RECR, the first stage via AHR is necessary.

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Effect of laser pulse time profile on its absorption by argon clusters

Cited by 11 publications

References 40 publications

Anharmonic resonance absorption of short laser pulses in clusters: A molecular dynamics simulation study

Anharmonic resonance absorption of short laser pulses in clusters: A molecular dynamics simulation study

Molecular dynamic studies on anisotropic explosion of laser irradiated Xe cluster

Laser cluster interaction in ambient magnetic fields for accelerating electrons in two stages without external injection

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