分子の内殻励起と分子イオンのダイナミクス

Abstract

Inner-shell excitation and ionization of linear molecules using synchrotron radiation are discussed and explained on a basis of recent outcome by several groups. Symmetry of excited states has been precisely investigated using angular distributions of produced fragment ions as well as highly energy-resolved photoabsorption spectra in consideration of theoretical prediction. It has been found that angular distributions of ion-ion coincidence signals are powerful for clarifying structural change in the inner-shell excited states of polyatomic molecules. These findings originate from fast decomposition processes following inner-shell excitation. The inner-shell hole is filled through Auger electron emission, and this emission is closely examined in these years because the Auger initial state can be clearly specified using intense monochromatic soft X-rays. Interference phenomenon between vibrational motion and core-hole lifetime has been observed in de-excitation spectra of diatomic molecules. Dissociation mechanism has been discussed using branching ratios and kinetic energies of fragment ions, and an Auger-electron fragment-ion coincidence technique is highly efficient for identifying excited molecular ion states before decomposition. A mapping technique of flight time of two fragment ions is utilized for clarifying correlation in kinetic energies and angular distributions among dissociation products in polyatomic molecules. Effect of vibrational excitation on dissociation is being studied through a progress in a brilliant and highly monochromatic soft X-ray instrument.