Thermalization of a UV laser ablation plume in a background gas: From a directed to a diffusionlike flow

Salvatore Amoruso, Bo Toftmann, and Jørgen Schou

Phys. Rev. E 69, 056403 – Published 14 May 2004

Abstract

Combined diagnostic measurements of deposition rates and ion time-of-flight signals have been employed to study the expansion of a laser ablation plume into a background gas. With increasing gas pressure the angular distribution of the collected ablated atoms becomes broader, while the total collected yield decreases. The total collected yield shows three separate regimes with increasing pressure, a vacuumlike regime, a transition regime with increasing plume broadening and splitting of the ion signal, and at the highest pressure a diffusionlike regime with a broad angular distribution. In the high-pressure regime the expansion can be described by a simple model based on diffusion from a confined plume.

Received 16 January 2003

DOI:https://doi.org/10.1103/PhysRevE.69.056403

Authors & Affiliations

Salvatore Amoruso

Coherentia-INFM, and INFM Unitá di Napoli, Dipartimento di Scienze Fisiche, Università di Napoli Federico II, Complesso Universitario di Monte S. Angelo, Via Cintia, I-80126 Napoli, Italy

Bo Toftmann and Jørgen Schou^*

OPL, Risø National Laboratory, DK-4000 Roskilde, Denmark

^*Corresponding author. Email address: j.schou@risoe.dk

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Vol. 69, Iss. 5 — May 2004

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Images

Figure 1
Upper part, the experimental setup; lower part, angular distribution of the ablated Ag particles as a function of angle with respect to the normal. Closed circles, $3.9 \times 10^{- 6} mbar$ ; open circles, $5.4 \times 10^{- 2} mbar .$ The curves are fits to Eq. (1) with $k_{z} = 3.0 \pm 0.2$ (closed circles) and $k_{z} = 2.5 \pm 0.2$ (open circles). Fluence: $2.5 J ∕ {cm}^{2}$ .Reuse & Permissions
Figure 2
Upper part: angular distribution of the collected ablation yield as a function of argon pressure. The distribution has been normalized to the maximum. The curves are fits to Eq. (1). For Argon: (●) ${2.0 \times 10}^{- 2} mbar$ ; (∎) ${1.0 \times 10}^{- 1} mbar$ ; (▴) ${1.5 \times 10}^{- 1} mbar$ ; (♠) ${2.3 \times 10}^{- 1} mbar$ . Lower part: The full width at half maximum $Δ θ$ of the angular distribution of the collected Ag atoms as a function of Ar background pressure. The dashed line has been inserted to guide the eye. Fluence: $2 J ∕ {cm}^{2}$ .Reuse & Permissions
Figure 3
Upper part: angular distribution of the collected ablation yield as a function of oxygen pressure. The distribution has been normalized to the maximum. The curves are fits to Eq. (1). For Oxygen: (●) ${4.8 \times 10}^{- 3} mbar$ ; (∎) ${5.0 \times 10}^{- 2} mbar$ ; (▴) ${1.1 \times 10}^{- 2} mbar$ ; (♠) ${3.5 \times 10}^{- 1} mbar .$ Lower part: The full width at half maximum $Δ θ$ of the angular distribution of the collected Ag atoms as a function of $O_{2}$ background pressure. The dashed line has been inserted to guide the eye. Fluence: $2.5 J ∕ {cm}^{2} .$ Reuse & Permissions
Figure 4
Upper part: (a) Two ion signals in pressure regime (a), see lower part of the figure. (b) Ion signal in regime (b), (c) ion signal in regime (c). All signals collected with the planar probe at $20 °$ from the normal in the distance of $75 mm$ from the target. Fluence: $2.5 J ∕ {cm}^{2}$ . Lower part: total collected yield of Ag atoms (closed circles, dotted curve, left axis). The collected yield has been obtained from an integration of Eq. (1) over the full hemisphere. Time-integrated ion yield from the probe (open circles, dashed curve, right axis) as a function of the Ar pressure normalized to the total collected yield for “vacuum.” The ion yield has been obtained by integrating the ion signals in the upper part with respect to time. Fluence: $2.5 J ∕ {cm}^{2}$ .Reuse & Permissions
Figure 5
Total collected yield (as in Fig. 4, lower part) as a function of Ar (closed circles) and Xe (open circles) pressure. The curves are fits to Eq. (3) with $τ = 3.4 ms$ (Ar) and $τ = 0.9 ms$ (Xe). The inset shows the geometry for Eq. (3).Reuse & Permissions
Figure 6
Fits of the total collected yield in an Ar background gas to Eq. (3) with $τ$ as a parameter. The data are from Fig. 5.Reuse & Permissions

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