Schematic overview of the experimental setup.
Time-resolved shadowgraph images of laser ablation of Cu target in (a) normal liquid helium (2.3 K) and (b) superfluid helium (1.6 K). Laser pulse energy was 5 mJ/pulse. The metal cluster populations are highlighted by red circles. The times at which the snapshots were taken are indicated in each frame. The ablation target is located on the right and shown in black.
Time-resolved shadowgraph images of laser ablation of sterling silver surface in superfluid helium at 1.7 K. The stack of ablation targets is on the left and appears in black. The target in the middle of the stack is ablated with 1 mJ/pulse laser pulse energy.
Static binding energies of selected impurities to a ground state vortex line. R represents the impurity-vortex core distance and E the total energy of the system.
Static binding energies of large heliophobic impurities to a ground state vortex line. R represents the impurity-vortex core distance and E the total energy of the system. The R s values correspond to the exponentially repulsive potential shifts as specified in Eq. (2) with the corresponding approximate barycenter radii given in parentheses.
Liquid density contours from DFT calculations for two Ag atoms trapped at the center of a vortex line. The coordinate for Ag-Ag recombination is indicated along the vortex line core. The minimum energy is reached when Ag resides at the center of the vortex line. The relevant length scales are indicated through the vortex core and the impurity bubble diameters. The contour value was set just above the bulk liquid density at 0 K (0.021836 Å−3 32 ) to highlight the vortex line and Ag solvation shell structures.
Plot of the calculated static impurity-vortex line binding energies (E Im-Vortex) as a function of the impurity solvation cavity barycenter radius (R). The open circles represent the DFT calculation results and the continuous red line corresponds to Eq. (4) with R′ = 1.35 Å. R s values represent the radial shifts in the purely exponential potential (see Eq. (2) ), which were used to approximate the behavior of larger metal clusters.
Plot of the calculated static impurity-vortex line repulsive barrier heights (E r ) as a function of the impurity solvation cavity barycenter radius (R). The open circles represent the results from the DFT calculations and the continuous red line corresponds to a least squares fit of Eq. (5) to the DFT data. R s denotes the radial shift in the purely exponential potential (see Eq. (2) ), which was used to mimic the behavior of large heliophobic clusters.
Overview of the pair potentials applied in the DFT calculations where L indicates linear geometry, T the perpendicular approach, and S spherically averaged potential (i.e., (L + 2T)/3). R m denotes the potential minimum, E m the potential energy at the minimum, A 0, …,A 5 are potential parameters given in atomic units (a.u.) according to Eq. (2) with R s = 0, and R V gives the minimum distance where the parametrization is still valid.
Article metrics loading...
Full text loading...