Dynamics of High-energy Electrons Generated by Picosecond X-ray Pulses in Organic Materials: A Basic Study toward X-ray Nano-fabrication

摘要

Two methods to generate x-ray pulses were developed: one of which is a femtosecond-laser-induced x-ray generation method from highly-concentrated alkali metal salts aqueous solutions and the other is a photo-excitable x-ray tube with femtosecond infrared laser pulses. Such a picosecond x-ray pulsed light source was applied for the study on a decay dynamics of x-ray-generated high-energy electrons in organic microcrystals of anthracene (ANT), 9,10-dichloroanthracene (DCA), and 9,10-dibromoanthracene (DBA) by performing time-resolved fluorescence measurements with a streak camera. This knowledge is indispensable for x-ray nano-fabrication of organic materials that will be performed in near future. A fluorescence rise time became shorter in the order of ANT > DCA DBA when excited by x-ray pulses, while the times when excited by ultraviolet laser pulses were the same corresponding to the system response function of the streak camera. Such behavior characteristic to x-ray pulsed excitation was studied from a viewpoint of high-energy electron decay processes characterized by stopping power and electron range.