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Title: Plasma induced by resonance enhanced multiphoton ionization in inert gas

Abstract

We present a detailed model for the evolution of resonance enhanced multiphoton ionization (REMPI) produced plasma during and after the ionizing laser pulse in inert gas (argon, as an example) at arbitrary pressures. Our theory includes the complete process of the REMPI plasma generation and losses, together with the changing gas thermodynamic parameters. The model shows that the plasma expansion follows a classical ambipolar diffusion and that gas heating results in a weak shock or acoustic wave. The gas becomes involved in the motion not only from the pressure gradient due to the heating, but also from the momentum transfer from the charged particles to gas atoms. The time dependence of the total number of electrons computed in theory matches closely with the results of coherent microwave scattering experiments.

Authors:
; ;  [1]
  1. Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544 (United States)
Publication Date:
OSTI Identifier:
21057546
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 102; Journal Issue: 12; Other Information: DOI: 10.1063/1.2825041; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; AMBIPOLAR DIFFUSION; ARGON; CHARGED PARTICLES; ELECTRONS; LASERS; MICROWAVE RADIATION; MOMENTUM TRANSFER; PHOTOIONIZATION; PHOTON-ATOM COLLISIONS; PLASMA; PLASMA DIAGNOSTICS; PLASMA EXPANSION; PLASMA HEATING; PLASMA PRODUCTION; PRESSURE GRADIENTS; PULSES; RESONANCE; SHOCK WAVES; SOUND WAVES; TIME DEPENDENCE

Citation Formats

Shneider, Mikhail N., Zhang Zhili, and Miles, Richard B.. Plasma induced by resonance enhanced multiphoton ionization in inert gas. United States: N. p., 2007. Web. doi:10.1063/1.2825041.
Shneider, Mikhail N., Zhang Zhili, & Miles, Richard B.. Plasma induced by resonance enhanced multiphoton ionization in inert gas. United States. doi:10.1063/1.2825041.
Shneider, Mikhail N., Zhang Zhili, and Miles, Richard B.. 2007. "Plasma induced by resonance enhanced multiphoton ionization in inert gas". United States. doi:10.1063/1.2825041.
@article{osti_21057546,
title = {Plasma induced by resonance enhanced multiphoton ionization in inert gas},
author = {Shneider, Mikhail N. and Zhang Zhili and Miles, Richard B.},
abstractNote = {We present a detailed model for the evolution of resonance enhanced multiphoton ionization (REMPI) produced plasma during and after the ionizing laser pulse in inert gas (argon, as an example) at arbitrary pressures. Our theory includes the complete process of the REMPI plasma generation and losses, together with the changing gas thermodynamic parameters. The model shows that the plasma expansion follows a classical ambipolar diffusion and that gas heating results in a weak shock or acoustic wave. The gas becomes involved in the motion not only from the pressure gradient due to the heating, but also from the momentum transfer from the charged particles to gas atoms. The time dependence of the total number of electrons computed in theory matches closely with the results of coherent microwave scattering experiments.},
doi = {10.1063/1.2825041},
journal = {Journal of Applied Physics},
number = 12,
volume = 102,
place = {United States},
year = 2007,
month =
}
  • We show that strong non-Franck--Condon effects observed in (2+1) resonance enhanced multiphoton ionization of the C /sup 3/Pi/sub g/ state of O/sub 2/ are due to the ksigma/sub u/ shape resonance previously observed in single-photon studies of diatomic molecules. Calculated vibrational branching ratios for the v' = 2,3 levels of the C /sup 3/Pi/sub g/ state are in reasonable agreement with experiment. Certain discrepancies remain in comparing theoretical results with the measured spectra, and possible electron-correlation effects which underly this are discussed.
  • We describe an experimental setup in which resonance-enhanced multiphoton ionization (REMPI) is used for diagnosis of neutral particles (atoms or molecules) effusing from a plasma. Quantum-state-specific detection, achieved by selective ionization with the help of REMPI, yields the distribution over their internal degrees of freedom. Discrimination against nonlaser-produced ions is performed by means of the combination of an electric and a magnetic field. The applicability of the setup is demonstrated by the determination of the rotational temperature of ground-state hydrogen molecules in a multicusp ion source. Under nondischarge conditions a detection limit is achieved of approx. =2 x 10/sup 10/more » state-selected hydrogen molecules/cm/sup 3/, corresponding to a value of approx. =7 x 10/sup 8//cm/sup 3/ at the analysis region. Under discharge conditions, this detection limit is deteriorated by the presence of metastable hydrogen molecules, which are ionized in a one-photon process.« less
  • We present numerical kinetic modeling of generation and evolution of the plasma produced as a result of resonance enhanced multiphoton ionization (REMPI) in Argon gas. The particle-in-cell/Monte Carlo collision (PIC/MCC) simulations capture non-equilibrium effects in REMPI plasma expansion by considering the major collisional processes at the microscopic level: elastic scattering, electron impact ionization, ion charge exchange, and recombination and quenching for metastable excited atoms. The conditions in one-dimensional (1D) and two-dimensional (2D) formulations correspond to known experiments in Argon at a pressure of 5 Torr. The 1D PIC/MCC calculations are compared with the published results of local drift-diffusion model, obtained formore » the same conditions. It is shown that the PIC/MCC and diffusion-drift models are in qualitative and in reasonable quantitative agreement during the ambipolar expansion stage, whereas significant non-equilibrium exists during the first few 10 s of nanoseconds. 2D effects are important in the REMPI plasma expansion. The 2D PIC/MCC calculations produce significantly lower peak electron densities as compared to 1D and show a better agreement with experimentally measured microwave radiation scattering.« less
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