Coulomb explosion of K-shell ionized krypton clusters studied by multiple-ion coincidence momentum imaging

The Coulomb explosion of K-shell ionized krypton clusters with an average size < N > of 160 has been studied by electron-multiple-ion-coincidence measurements in which the time-of-flight (TOF) of ions was measured by using a position sensitive detector. The authors have sorted the TOF spectra by the number of coincidence ion signals, N-coin, and found that singly charged fragment ions such as Kr+, Kr-2(+), and Kr-3(+) are dominant for N-coin >= 2, and that multiply charged ions are detected mainly for N-coin=1. The N-coin dependence of the peak widths in the TOF spectra reveals that the average momentum of the Kr+ ions increases with N-coin, while those of Kr-2(+) and Kr-3(+) decrease. These results have been more directly confirmed by the momentum imaging measurements. The authors propose that the heavier ions are produced in the central part of clusters where the Coulomb interactions from the surrounding ions are more effectively canceled out due to the higher symmetry. (c) 2007 American Institute of Physics.