Scaling law of angular emission distributions of laser ablated particle pulses from monoatomic and compound targets

The fundamental determining factor of angular emission of multiple charged ions ejected by laser ablation of different metals and their binary alloys

“…In the present investigations, we have extended the work of Ali et al [1] carried out for mono-atomic targets to bi-atomic targets using the abundant wealth of data obtained by Srivastava and Rohr [10] and Srivastava et al [11] to find out whether the angular distribution of individual ionization states as well as total charge of LPP ions of pure metals and their binary alloy targets have any systematic correlation with the room temperature DebyeeWaller thermal parameter B or not? Another objective was to show that a given angular distribution of laser-ablated particles described by Gaussian function can also be encompassed by cosine power-law equally well; exponent n of cos n q distribution function as well as FWHM 2s of Gaussian function both correlate very well with the most fundamental microscopic property, i.e.…”

“…However, they found that the mass dependence of exponent n approximately follows M 3/4 e law. Similarly, Srivastava and Rohr [10] have reported a different scaling law for the angular emission distribution of laser-ablated particles from mono-atomic (Al, Ti, Cu, Mo, W) and alloy targets (Ti 25 30 ). For a given laser energy and a fixed focal spot size, the width of angular emission cone (FWHM) 2s was shown to follow a hyperbolic law: 2s ¼ k/M þ d, where k and d are numerical constants, and M is atomic mass of element targets or average atomic mass [M ¼ (M 1 c 1 þ M 2 c 2 )] of binary alloy targets, where M 1 and M 2 are atomic masses of the constituent elements whereas c 1 and c 2 are their atomic concentrations expressed as fraction.…”

On the applicability of laser ionization for simulating hypervelocity impacts

“…37 In this range the ion formation is only dependent on the surface properties and the wavelength of the laser light, implying a desorption mechanism of ion formation. 38 Thus, the energy of the ions is determined by the photon energy of the laser light and subsequently only varies within a very small range.…”

Angular and energy distribution of Sn ion debris ejected from a laser-produced plasma source, for laser power densities in the range suitable for extreme ultraviolet lithography

“…3, indicating that lower energy ions are ejected at larger angles, but also that ions of a given energy are ejected with a Gaussian distribution around a preferential angle of emission. The sum of these Gaussians, describing the preferential angle of emission for different energy ions, gives rise to the more commonly applied cos n ðhÞ fit 10,11,30,37,38 or Gaussian distribution 39,40 used to describe the total angular emission of LPP ions. Double Gaussians were required at the lowest energies and are likely to be associated with an angularly broad thermal contribution, on which is superimposed a narrow emission at large angles relative to target normal.…”

“…Laska et al 39 presented evidence that a cosine or a Gaussian distribution provide nearly identical fits to such ion distributions. Srivastava et al 40 argued that a Gaussian distribution possesses a more credible physical basis for describing the angular distribution of ions, due to the coupling of the spatial Gaussian intensity distribution of the incident laser pulse to the angular emission of ions. The experimental data shown in Fig.…”