Velocity distributions of Ba (S01, DJ3, D21, P13, and P11) and Ba+(P3∕22) produced by 1064nm pulsed laser ablation of barium in vacuum

Rossa, Maximiliano; Rinaldi, Carlos A.; Ferrero, Juan C.

doi:10.1063/1.2352807

Cited by 11 publications

(18 citation statements)

References 19 publications

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“…[7][8][9] Some 1D simulations of the plasma fluid in the plume have also been carried out which provide information about the gross characteristic features of the plume (e.g., evolution of maximum temperature, translational velocity, etc.). In addition some authors 9 have attributed the plume splitting (appearance of double peaked structure in the ion time of flight (TOF) distribution) to the formation of electric fields (double layers) in the expanding plume.…”

Section: Introductionmentioning

confidence: 99%

Numerical modeling of plasma plume evolution against ambient background gas in laser blow off experiments

et al. 2012

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Two dimensional numerical modelling based on simplified hydrodynamic evolution for an expanding plasma plume (created by laser blow off) against an ambient background gas has been carried out. A comparison with experimental observations shows that these simulations capture most features of the plasma plume expansion. The plume location and other gross features are reproduced as per the experimental observation in quantitative detail. The plume shape evolution and its dependence on the ambient background gas are in good qualitative agreement with the experiment. This suggests that a simplified hydrodynamic expansion model is adequate for the description of plasma plume expansion. V C 2012 American Institute of Physics.

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Section: Introductionmentioning

confidence: 99%

Numerical modeling of plasma plume evolution against ambient background gas in laser blow off experiments

et al. 2012

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“…A detailed characterization of the resulting beam at the prevailing laser ablation conditions and in the absence of N 2 O scattering gas has been reported elsewhere. [8][9][10] The time-of-flight ͑TOF͒ technique through pulsed laser-induced fluorescence and time-resolved fluorescence detection was used to this goal. At 3.3 cm from the Ba disk surface where the chemiluminescence is probed, the barium beam is composed mainly of neutral atoms in the 6s 2 1 S 0 , 6s5d 3 D J , and 6s6p 3 P J states in an overall abundance Ͼ98% of that of the total Ba atoms.…”

Section: Methodsmentioning

confidence: 99%

“…Advantage was taken here of the ability to modify significantly the Ba͑ 3 P͒ velocity distribution by changing the laser ablation conditions of the atomic beam source used previously. [8][9][10] Average values for both the initial relative velocity and collision energy that have been reported in Ref. 8, where pure thermal conditions were erroneously assumed are recalculated here by applying a different procedure, which is appropriate to the present hyperthermal atomic beam-Maxwellian gas experiments.…”

Section: Introductionmentioning

confidence: 98%

Chemiluminescence from the Ba(P3)+N2O→BaO(A Σ1+)+N2 reaction: Collision energy effects on the product rotational alignment and energy release

Rossa¹,

Rinaldi²,

Ferrero³

2010

The Journal of Chemical Physics

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Both fully dispersed unpolarized and polarized chemiluminescence spectra from the Ba((3)P)+N(2)O reaction have been recorded under hyperthermal laser-ablated atomic beam-Maxwellian gas conditions at three specific average collision energies E(c) in the range of 4.82-7.47 eV. A comprehensive analysis of the whole data series suggests that the A (1)Sigma(+)-->X (1)Sigma(+) band system dominates the chemiluminescence. The polarization results revealed that the BaO(A (1)Sigma(+)) product rotational alignment is insensitive to its vibrational state upsilon(') at E(c)=4.82 eV but develops into an strong negative correlation between product rotational alignment and upsilon(') at 7.47 eV. The results are interpreted in terms of a direct mechanism involving a short-range, partial electron transfer from Ba((3)P) to N(2)O which is constrained by the duration of the collision, so that the reaction has a larger probability to occur when the collision time is larger than the time needed for N(2)O bending. The latter in turn determines that, at any given E(c), collinear reactive intermediates are preferentially involved when the highest velocity components of the corresponding collision energy distributions are sampled. Moreover, the data at 4.82 eV suggest that a potential barrier to reaction which favors charge transfer to bent N(2)O at chiefly coplanar geometries is operative for most of the reactive trajectories that sample the lowest velocity components. Such a barrier would arise from the relevant ionic-covalent curve crossings occurring in the repulsive region of the covalent potential Ba((3)P)cdots, three dots, centeredN(2)O((1)Sigma(+)); from this crossing the BaO(A (1)Sigma(+)) product may be reached through mixings in the exit channel with potential energy surfaces leading most likely to the spin-allowed b (3)Pi and a (3)Sigma(+) products. The variation with increasing E(c) of both the magnitude of the average BaO(A (1)Sigma(+)) rotational alignment and the BaO(A (1)Sigma(+)) rovibrational excitation, as obtained from spectral simulations of the unpolarized chemiluminescence spectra, consistently points to additional dynamic factors, most likely the development of induced repulsive energy release as the major responsible for the angular momentum and energy disposal at the two higher E(c) studied. The results of a simplified version of the direct interaction with product repulsion-distributed as in photodissociation model do not agree with the observed average product rotational alignments, showing that a more realistic potential energy surface model will be necessary to explain the present results.

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“…This assumption, though, might require closer scrutiny in situations where low-lying metastable states are expected to be present in the ablation plume. The kinetic energy distributions of such metastable species may also differ substantially from those of the ground-state atoms, as exemplified by an earlier time-of-flight ͑TOF͒ laser-induced fluorescence ͑LIF͒ study of the 1064 nm PLA of barium at = 5.3 J / cm 2 , 18 which in turn may have profound consequences on the quality of the deposited films of any suitable material. There are few reports of investigations of the electronic state populations of neutral atoms in plumes formed by PLA, involving only UV and visible ͑vis͒ laser wavelengths to compare with these thermal predictions.…”

Section: Introductionmentioning

confidence: 99%

“…There are few reports of investigations of the electronic state populations of neutral atoms in plumes formed by PLA, involving only UV and visible ͑vis͒ laser wavelengths to compare with these thermal predictions. 19,20 The present work was undertaken mainly as an attempt to explore this topic in the case of the infrared ͑IR͒ PLA of a metal target, which is likely to favor thermally rather than electronically driven material ablation, 13,18 and at a range of laser fluences which are appropriate for plasma formation above the target surface in order to get information on the primary process under ablation conditions of practical use.…”

Section: Introductionmentioning

confidence: 99%

Internal state populations and velocity distributions of monatomic species ejected after the 1064 nm laser irradiation of barium

Rossa

Rinaldi

Ferrero

2009

Journal of Applied Physics

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The plumes accompanying 1064 nm nanosecond pulsed laser ablation of barium in vacuum at three moderate incident laser fluences in the range of 5.3-10.8 J / cm 2 have been studied using both wavelength and time resolved optical emission spectroscopy and time-of-flight laser-induced fluorescence. Neutral atoms and both singly and doubly charged monatomic cations in excited states up to near the corresponding ionization limits are identified in the optical emission spectra. The population distributions of low-lying ͑Յ1.41 eV͒ "dark" states of Ba atoms measured by laser-induced fluorescence revel that the metastable 3 D J and 1 D 2 abundances in the plume are higher than predictions based on assuming a Boltzmann distribution. The 3 D J and 1 D 2 populations are seen, respectively, to decrease slightly and nearly no vary with raising fluence, which contrasts with the increasing trend that is observed in the ground-state Ba͑ 1 S 0 ͒ population. At all fluences, the time-of-flight distributions of the whole dark states and of various of the emitting levels are bimodal and well described by Maxwell-Boltzmann and shifted Maxwell-Boltzmann velocity functions, respectively, with different average translational temperatures ͗T͘ for each state. The ͗T͘ values for the dark states are insensitive to the fluence, while for all emitting species marked variations of ͗T͘ with fluence are found. These observations have been rationalized in terms of material ejection from the target being dominated by a phase explosion mechanism, which is the main contributor to the Ba͑ 1 S 0 ͒ population. Thermionic emission from the target surface can also release initial densities of free electrons and cations which, at the prevailing irradiances, will arguably interact with the incident laser radiation by inverse bremsstrahlung, leading to further excitation and ionization of the various plume species. Such a heating mechanism ensures that the energy injected to the plume will alter the propagation velocities of the primary inverse bremsstrahlung absorbers, i.e., cations, to a major extent than those of neutral atoms with increasing fluence. Electron-ion recombination occurring early in the plume expansion can lead to the generation of both neutral and ionic species in a manifold of long-lived Rydberg states, from which a radiative cascade will likely ensue. The distinct fluence dependences of the Ba͑ 3 D J ͒ and Ba͑ 1 D 2 ͒ populations and velocity distributions show up the major complexity that distinguishes their populating mechanisms with respect to the remaining species.

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Velocity distributions of Ba (S01, DJ3, D21, P13, and P11) and Ba+(P3∕22) produced by 1064nm pulsed laser ablation of barium in vacuum

Cited by 11 publications

References 19 publications

Numerical modeling of plasma plume evolution against ambient background gas in laser blow off experiments

Numerical modeling of plasma plume evolution against ambient background gas in laser blow off experiments

Chemiluminescence from the Ba(P3)+N2O→BaO(A Σ1+)+N2 reaction: Collision energy effects on the product rotational alignment and energy release

Internal state populations and velocity distributions of monatomic species ejected after the 1064 nm laser irradiation of barium

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