TY - JOUR
T1 - Kinetic energy distribution of multiply charged ions in Coulomb explosion of Xe clusters
AU - Heidenreich, Andreas
AU - Jortner, Joshua
N1 - Funding Information:
We are greatly indebted to Professor Isidore Last for many discussions and for extensive exchange of information. We are grateful to Professor Uzi Even for discussions of the laser-intensity profiles. Computation time and technical and manpower support of the computation center IZO-SGI SDIker of the University of the Basque Country (UPV/EHU), provided by the Spanish Ministry of Science and Education (MICINN), by the Basque Government (GV/EJ), and by the European Social Fund (ESF), are gratefully acknowledged. This research was supported in part by the Saiotek Program (GV/EJ), by the Binational German-Israeli James Franck Program on laser-matter-interaction at Tel Aviv University, and by the Deutsche Forschungsgemeinschaft (DFG) SFB 450 program on “Analysis and Control of Ultrafast Photoinduced Reactions” at the Humboldt University and at the Free University of Berlin.
PY - 2011/2/21
Y1 - 2011/2/21
N2 - We report on the calculations of kinetic energy distribution (KED) functions of multiply charged, high-energy ions in Coulomb explosion (CE) of an assembly of elemental Xen clusters (average size n 200-2171) driven by ultra-intense, near-infrared, Gaussian laser fields (peak intensities 10 15- 4 1016 W cm-2, pulse lengths 65-230 fs). In this cluster size and pulse parameter domain, outer ionization is incompletevertical, incompletenonvertical, or completenonvertical, with CE occurring in the presence of nanoplasma electrons. The KEDs were obtained from double averaging of single-trajectory molecular dynamics simulation ion kinetic energies. The KEDs were doubly averaged over a log-normal cluster size distribution and over the laser intensity distribution of a spatial Gaussian beam, which constitutes either a two-dimensional (2D) or a three-dimensional (3D) profile, with the 3D profile (when the cluster beam radius is larger than the Rayleigh length) usually being experimentally realized. The general features of the doubly averaged KEDs manifest the smearing out of the structure corresponding to the distribution of ion charges, a marked increase of the KEDs at very low energies due to the contribution from the persistent nanoplasma, a distortion of the KEDs and of the average energies toward lower energy values, and the appearance of long low-intensity high-energy tails caused by the admixture of contributions from large clusters by size averaging. The doubly averaged simulation results account reasonably well (within 30) for the experimental data for the cluster-size dependence of the CE energetics and for its dependence on the laser pulse parameters, as well as for the anisotropy in the angular distribution of the energies of the Xeq ions. Possible applications of this computational study include a control of the ion kinetic energies by the choice of the laser intensity profile (2D3D) in the laser-cluster interaction volume.
AB - We report on the calculations of kinetic energy distribution (KED) functions of multiply charged, high-energy ions in Coulomb explosion (CE) of an assembly of elemental Xen clusters (average size n 200-2171) driven by ultra-intense, near-infrared, Gaussian laser fields (peak intensities 10 15- 4 1016 W cm-2, pulse lengths 65-230 fs). In this cluster size and pulse parameter domain, outer ionization is incompletevertical, incompletenonvertical, or completenonvertical, with CE occurring in the presence of nanoplasma electrons. The KEDs were obtained from double averaging of single-trajectory molecular dynamics simulation ion kinetic energies. The KEDs were doubly averaged over a log-normal cluster size distribution and over the laser intensity distribution of a spatial Gaussian beam, which constitutes either a two-dimensional (2D) or a three-dimensional (3D) profile, with the 3D profile (when the cluster beam radius is larger than the Rayleigh length) usually being experimentally realized. The general features of the doubly averaged KEDs manifest the smearing out of the structure corresponding to the distribution of ion charges, a marked increase of the KEDs at very low energies due to the contribution from the persistent nanoplasma, a distortion of the KEDs and of the average energies toward lower energy values, and the appearance of long low-intensity high-energy tails caused by the admixture of contributions from large clusters by size averaging. The doubly averaged simulation results account reasonably well (within 30) for the experimental data for the cluster-size dependence of the CE energetics and for its dependence on the laser pulse parameters, as well as for the anisotropy in the angular distribution of the energies of the Xeq ions. Possible applications of this computational study include a control of the ion kinetic energies by the choice of the laser intensity profile (2D3D) in the laser-cluster interaction volume.
UR - http://www.scopus.com/inward/record.url?scp=79951891242&partnerID=8YFLogxK
U2 - 10.1063/1.3521476
DO - 10.1063/1.3521476
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AN - SCOPUS:79951891242
SN - 0021-9606
VL - 134
JO - Journal of Chemical Physics
JF - Journal of Chemical Physics
IS - 7
M1 - 074315
ER -