High-charge Coulomb explosions of clusters in ultra-dense deuterium D(−1)

Abstract

Laser-induced Coulomb explosions of clusters D N in ultra-dense deuterium D(−1) show a broad spectrum of fragmentation processes. For small clusters D 3 and D 4 symmetric fragmentation processes are often observed. Experiments now show that these clusters fragment by maximum-charge processes, like D 4 4+ → 4D +, each fragment leaving with 945 eV kinetic energy. This is the case even at low laser pulse intensities of <10 12 W cm −2. The facile laser field ionization of these clusters is probably caused by their small size. Such high-charge processes seem to be most common in the superfluid condensed phase. A centrifugal stretching in the clusters is observed, giving 5–8% longer D–D bonds at higher average laser intensity, probably at J ≤ 3. Rotational excitation of D 2 + fragments is often apparent at similar J values. This requires strong bonding between the two deuterons, predicted to be close to 700 eV due to strong exchange interaction.