Schematic of the experimental setup.
(a) Schematic of target sample and (b) AFM lineout scan of the single ablation spot at 170 nJ.
Temporal evolution of plasma plume at various background pressures: (a) 2.3 Torr, (b) 29 Torr, and (c) at ambient air pressure. The time T denotes the delay after the laser pulse for the end of the 5 ns integration period.
Images of plasma plume for an accumulation end time of 11 ns from the onset of the laser pulse for various pressures. The laser enters from the bottom.
Contour plot of the slow component plume at background pressures of (a) 0.3 Torr, (b) 18.5 Torr, and (c) 52 Torr. Time T denotes delay after the laser pulse.
Position of the leading front of the chromium plasma plume produced in background gas pressure of (a) 0.3 Torr, (b) 5.5 Torr, (c) 18.5 Torr, and (d) 52 Torr obtained from the gated ICCD images at different times. Experimental data points ( ), linear fit (•), blastwave calculation ( ), and drag model fit (–) are shown with different fitting parameters. For the drag model β = 0.06 ± 0.01 ns−1 at 5.5 Torr, β = 0.1 ± 0.04 ns−1 at 18.5 Torr, and β = 0.15 ± 0.06 ns−1 at 52 Torr
Plume length L of the chromium plasma at different ambient pressures. Experimental plume length ( ), plume emission length (★), and calculated values (-◁)
Temporal plasma plume expansion at 19 Torr background pressure with laser pulse energies of 26 nJ (left) and 33 nJ (right). Time, T, denotes delay after the laser pulse. The laser is incident from the right.
Integrated intensity counts for the plume images for different laser pulse energies.
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