Charged Particle Oscillations in Transient Plasmas Generated by Nanosecond Laser Ablation on Mg Target

Abstract

The dynamics of a transient plasma generated by laser ablation on a Mg target was investigated by means of the Langmuir probe method and fractal analysis. The empirical data showcased the presence of an oscillatory behavior at short expansion times (<1 μs) characterized by two oscillation frequencies and a classical behavior for longer evolution times. Space- and time-resolved analysis was implemented in order to determine main plasma parameters like the electron temperature, plasma potential, or charged particle density. In the motion fractal paradigm, a theoretical model was built for the description of laser-produced plasma dynamics expressed through fractal-type equations. The calibration of such dynamics was performed through a fractal-type tunneling effect for physical systems with spontaneous symmetry breaking. This allows both the self-structuring of laser-produced plasma in two structures based on its separation on different oscillation modes and the determination of some characteristics involved in the self-structuring process. The mutual conditionings between the two structures are given as joint invariant functions on the action of two isomorph groups of SL(2R) type through the Stoler-type transformation, explicitly given through amplitude self-modulation.

Investigation of laser‐produced plasma multistructuring by floating probe measurements and optical emission spectroscopy

“…To have an overall understanding of the ns laser-produced Ag plasma properties at distances that correspond to the usual location of the substrate during the PLD process, we chose to perform time-resolved analysis on the main expansion axis (90°). The technique has been eloquently presented in a series of papers [20,22,24,28] and will help us to understand the late-time dynamics of the ejected electrons. The focus on the electronic region of the I-V characteristics comes from the implementation of the LP theory, which assumes that the ions have a considerably lower mobility than electrons.…”

Non-Linear Behaviors of Transient Periodic Plasma Dynamics in a Multifractal Paradigm

“…We do see the evolution contains simple oscillatory behavior-damped oscillation-modulated dynamics. The oscillatory regime (classical and damped) has already been reported on and was reported more intensely for laser-produced plasma in the past 10 years [8][9][10]18,19]. While the oscillating dynamics are relatively new, the modulated and the multiple structuring of the plasma has been reported as early as 1990, with initial reports engaging the plasma-gas particle interaction as the main drive for the structuring and the most recent ones considering the multiple ablation mechanism for the presence of groups of particles with different properties [10].…”

“…Some differential procedures cannot be sued when tackling the analysis of complex processes that can imply non-linearity and chaos related to plasma dynamics [6,7]. If non-differentiability can be seen as a global property of the transient plasma [8][9][10], we can build a non-differentiable theoretical structure for describing the dynamics of the periodic phenomena in transient plasmas. Taking into account that the complexity of the interaction processes is completely substituted by non-differentiability, we are not confined by the use of the entirety of classical quantities from differentiable plasma physics.…”

A Theoretical Multifractal Model for Assessing Urea Release from Chitosan Based Formulations

“…In Figure 4, the 3D representation of the release mass variation in time and space and the fit of the experimental data using our model are presented. The model was calibrated [22][23][24] to fit the empirical data presented in the previous section. It can be observed that the multifractal model accurately predicts the behavior seen empirically with a steep increase for a short moment of time and a saturation plateau for considerably longer periods.…”

“…Our fundamental hypothesis is that the structural units' dynamics in the polymer-drug complex systems are described by continuous but non-differentiable curves (multifractal curves). In such a context the drug release dynamics will be described through the multifractal theory of motion in the form of hydrodynamic regimes at various resolution scales (multifractal hydrodynamic model [19][20][21][22][23][24]).…”