Development of methods for the analysis of physical properties of free clusters by using inner-core excitation

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We proposed a new method for measuring the electron transport in free cluster and developed a new instrument to carry out this method. The instrument consists of a 2D detector and a time of flight mass spectrometer. Both the electron ion coincidence (EICO) and the multi-hit momentum imaging (MHMI) of deep inner-core excited nano-particles were carried out by this instrument. In MHMI measurements, the charge-to-mass ratio and the momentum of fragment ions emitted from inner-core excited nano-particles are obtained from the time of flight and position of ions. An insight into the mobility of the holes can be deduced from the analysis of the momentum of fragment ions. In addition, we developed a new cluster source to produce the core-shell type ternary alloy cluster of an arbitrary composition.The EICO spectra for Ar_<99>Kr_1 clusters reveal that singly charged ions are emitted from the inner-core excited clusters in addition to the multiple charged ions. The dependence of the EICO spectra on photon energy and cluster size suggests that the holes created through vacancy cascade on the krypton atoms are transferred to the surrounding atoms, and that the singly charged ions are the primary product of the krypton photoabsorption. Charge localization is suggested for the inner-core excited mixed rare-gas clusters from the analysis of the momentum of daughter ions.We have carried out the MHMI measurements of bromophenol and bromobiphenyl. Both molecules have emitted many fragment ions as a result of inner-core excitation of bromine. The analysis of the relative abundance of multiple charged ions suggests the decrease of the charge migration from bromine atom to oxygen atom as the increase of molecular length.Our results suggest that the hard x-ray is of use to study the charge mobility of nano-particles such as clusters and single molecules.