Mechanisms of resonant laser ionization

Leonov, A. G.; Chekhov, D. I.; Starostin, A. N.

doi:10.1134/1.558204

Cited by 12 publications

(7 citation statements)

References 30 publications

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“…We attribute the increase in both the neutral and the ionic emission to heating of the Nd:YAG plasma by the coincident CO 2 laser [2]. Such inverse bremstrahlung absorption of CO 2 laser radiation in the free electrons of a plasma is well known in laser cutting and welding and can, in extreme cases, result in a "plasma mirror" attenuation of the incident CO 2 beam [2,[14][15]. While the exact mechanism occurring may be related to the inverse bremsstrahlung effect or a coupling to a Townsend discharge, we are conducting more detailed experiments to study the details of the enhanced emission process.…”

Section: Discussion and Mechanismsmentioning

confidence: 99%

Enhancement of Nd:YAG LIBS emission of a remote target using a simultaneous CO_2 laser pulse

Killinger¹,

Allen²,

Waterbury³

et al. 2007

Opt. Express

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For the first time to the best of our knowledge, a simultaneous 10.6 mum CO(2) laser pulse has been used to enhance the Laser Induced Breakdown Spectroscopy (LIBS) emission from a 1.064 mum Nd:YAG laser induced plasma on a hard target. The enhancement factor was on the order of 25 to 300 times, depending upon the emission lines observed. For an alumina ceramic substrate the Al emission lines at 308 nm and Fe impurity line at 278 nm showed an increase of 60x and 119x, respectively. The output energy of the Nd:YAG laser was 50 mJ/pulse focused to a 1 mm diameter spot to produce breakdown. The CO(2) laser pulse had a similar energy density of 40 mJ/mm(2). Timing overlap of the two laser pulses within 1 microsecond was important for enhancement to be observed. An observed feature was the differential enhancement between different elemental species and also between different ionization states, which may be helpful in the application of LIBS for multi-element analysis.

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Section: Discussion and Mechanismsmentioning

confidence: 99%

Enhancement of Nd:YAG LIBS emission of a remote target using a simultaneous CO_2 laser pulse

Killinger¹,

Allen²,

Waterbury³

et al. 2007

Opt. Express

View full text Add to dashboard Cite

show abstract

“…To give a deeper understanding about the time at which this reaction occurs. Figure 6 show that 5.0x10 11 1.0x10 12 4.0x10 3 6.0x10 3 8.0x10 3 1.0x10 4 1.2x10 4 1.4x10 4 1. the omission of this reaction does not affect.…”

Section: The Time Evolution Of Electron Energy Distribution Functionmentioning

confidence: 98%

Numerical Investigation of the Tri-Atomic Ions Formation during Laser Ionization Based on Resonance Saturation

Abdelati¹,

Mahmoud²,

Gamal³

2014

JAMP

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We present a theoretical investigation of plasma generation in sodium vapor induced by laser radiation tuned to the first resonance line (3S-3P) at λ = 589 ns. A set of rate equations that describe the rate of change of the ground and excited states population as well as the temporal variation of the electron energy distribution function (EEDF), beside the formed atomic ion Na + , molecular ion + 2 Na and tri-atomic ions + 3 Na are solved numerically. The calculations are carried out at different laser energy and different sodium atomic vapor densities under the experimental conditions of Tapalian and Smith (1993) to test the existence of the formed tri-atomic ions. The numerical calculations of the electron energy distribution function (EEDF) show that a deviation from the Maxwellian distribution due to the super elastic collisions effect. In addition to the competition between associative ionization (3P-3P), associative ionization (3P-3D) and Molnar-Hornbeck ionization processes for producing + 2 Na , the calculations have also shown that the atomic ions Na + are formed through the Penning ionization and photoionization processes. These results are found to be consistent with the experimental observations.

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“…The results of McIlrath and Lucatorto [2] were interpreted by Measures et al, [22] [23], on the basis of superelastic heating of electrons in colliding with the excited atoms (collisions of the second kind). The theoretical model that describes the formation of resonance plasma is referred to as LIBORS.…”

Section: The Pioneering Observation Of This Phenomenon Was Given By Mmentioning

confidence: 99%

Impact of Initial Electron Development on Sodium Plasma Generation Using LIBORS Technique: Numerical Modeling

Hamam¹,

Gamal²

2018

JMP

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The present work reports an investigation on the role played by Na 3+ ions formed through triatomic associative ionization collision of Na(4d) atoms with Na 2 ground state molecules during the early phase of sodium plasma generation by laser ionization based on resonance saturation (LIBORS). Such ionization mechanism is observed experimentally for the first time by Tapalian and Smith (1993) [1]. In their experiment, stepwise atomic excitations are created using two CW dye lasers; one laser is tuned to 589 nm to excite the Na(3s) to Na(3p) D2 transition of sodium and the other laser is tuned 569 nm to excite the Na(3p) to Na(4d) transition. The analysis is grounded on a numerical study of the role of seed electron processes on the temporal evolution of sodium plasma formation by laser irradiation. A previously developed numerical model based on LIBORS technique is modified and adopted. In the present study, the sodium atom is treated as an atom comprises 22 levels namely: a ground state, 18 excited states and three ionic states (atomic, molecular and tri-atomic). The model tackled various collisional and radiative processes that act to enhance and deplete the free electrons generated in the interaction region. The contribution of these processes is signified by solving numerically a system of time-dependent rate equations, which couple the generated atomic and ionic species with the laser fields. Meanwhile, it solves the time-dependent Boltzmann equation for the electron energy distribution function (EEDF) of the generated electrons. The computed values of the EEDF, time evolution of both excited states population and the formed ionic species considering the individual effect of associative ionization, Penning, and photo-ionization and triatomic associative ionization justified the important effect of each of these ionizing processes in creating the early stage electrons. These seed electrons are assumed to rapidly gain energy through superelastic collisions leading eventually to plasma development.How to cite this paper: Hamam, K.

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Mechanisms of resonant laser ionization

Cited by 12 publications

References 30 publications

Enhancement of Nd:YAG LIBS emission of a remote target using a simultaneous CO_2 laser pulse

Enhancement of Nd:YAG LIBS emission of a remote target using a simultaneous CO_2 laser pulse

Numerical Investigation of the Tri-Atomic Ions Formation during Laser Ionization Based on Resonance Saturation

Impact of Initial Electron Development on Sodium Plasma Generation Using LIBORS Technique: Numerical Modeling

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