Cluster dynamics transcending chemical dynamics toward nuclear fusion

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   Fig. 1.

   Snapshots of the time-resolved structures of (D₂)₂₁₇₁ (Left) and (HT)₂₁₇₁ (Right) clusters in a Gaussian laser field (I _M = 10¹⁸ W·cm⁻² at τ = 25 fs marked on the images), at three different times t − t _s. The lowest part of the image portrays the time axis and the electric field of the laser. The instants of the snapshots are marked on the time axis by a, b, and c. H atoms are represented in blue, T atoms in red, and electrons in light gray. (a) The initial nanoplasma at t − t _s = 0. (b) At t − t _s = 8.2 fs, the beginning of spatial expansion of the clusters is manifested. In case of the (HT)_n cluster, a shell of H⁺ ions is displayed. At this time, a large number of electrons are stripped by outer ionization, which occurs repeatedly when the electric field of the laser is close to a maximum. (c) At (t − t _s) = 13.0 fs, the spatial expansion and shell formation of the HT cluster is pronounced. Also, all nanoplasma electrons have been removed at this time.

   
   
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   Fig. 2.

   The radial distribution functions P(r) for the (D₂)₂₁₇₁, (HT)₂₁₇₁, and (DI)₂₁₇₁ clusters in a Gaussian laser field (I _M = 10¹⁸ W·cm⁻² and τ = 25 fs) at various times t − t _s. t _s is the starting time of the simulation with respect to the maximum of the Gaussian laser field envelope located at t = 0 (see Supporting Text). For the heteronuclear (HT)₂₁₇₁ and (DI)₂₁₇₁ clusters, P(r) = P(r)Δr is drawn separately for each ion (as marked on the images), exhibiting shell formations of the nonoverlapping distributions of different isotope/element ions at times t − t _s > 0. These shells expand with different velocities. (Insets) The time-dependent increase of the first moments 〈R〉 of P(r) relative to the first moment 〈R〉₀ at t − t _s = 0. Data are presented for different ions, as marked on Insets.

   
   
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   Fig. 3.

   The cluster size dependence of the maximal energies E _M (solid lines) and average energies E _av (dashed lines) of D⁺ ions in the uniform CE of (D₂)_n clusters and in the nonuniform CE of (CD₄)_n, (DI)_n, and (CD₃I)_n clusters at I = 10¹⁸ W·cm⁻² and τ = 25 fs. The simulation data manifest the (divergent) power law E _M, E _av ∝ n ^2/3. Slight deviations from this scaling dependence for small (DI)_n and (CD₃I)_n ECLHHs originate from ignition and screening effects for inner ionization (12). (Inset) The dependence of E _M and I _M for clusters marked on the curves.

   
   
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   Fig. 4.

   The kinetic energy distributions of D⁺ ions from several clusters (marked on the curves) at I _M = 10¹⁸ W·cm⁻² and τ = 25 fs. Three Insets show the simulated data (solid curves) and the results of the ELM (dashed curves) for CE of (D₂)₁₆₇₈₆, (CD₄)₄₂₁₃, and (DI)₄₂₁₃ clusters.

   
   
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   Fig. 5.

   Neutron yields per laser pulse (see text) for NFDCE of (D₂)_n, (CD₄)_n, (DI)_n, and (CD₃I)_n clusters in the intensity range 10¹⁷ to 10¹⁹ W·cm⁻².

   
   
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   Fig. 6.

   Yields of the ¹²C(p,γ)¹³N nucleosynthesis reaction, with the energetic ¹²C and H⁺ nuclei being produced by CE of (CH₃I)_n clusters at I = 10²⁰ W·cm⁻². The yields were calculated from the E _av ^(p) and E _av ^(C) energetic data together with the reaction cross sections (Inset adapted from ref. 23). The energetic data for n = 2,171 (R ₀ = 38 Å) and for n = 4,230 (R ₀ = 47.1 Å) were obtained from simulations (filled circles), whereas for the size domain n = 8,426 (R ₀ = 51.3 Å) to n = 33,700 (R ₀ = 94.1 Å) the energetic data were evaluated from the n ^2/3 scaling law.