| Budget Amount *help |
¥28,500,000 (Direct Cost: ¥28,500,000)
Fiscal Year 2000: ¥4,300,000 (Direct Cost: ¥4,300,000)
Fiscal Year 1999: ¥9,700,000 (Direct Cost: ¥9,700,000)
Fiscal Year 1998: ¥14,500,000 (Direct Cost: ¥14,500,000)
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| Research Abstract |
Microparticles, such as organic microcrystals, semiconductor powders, metallic beads, and liquid droplets, possess characteristic physical and chemical properties different from bulk materials. Although various kinds of spectroscopic techniques have been applied for elucidating reaction processes occurring in/on microparticles, these studies were performed by conventional time-resolved but space-unresolved spectroscopy so that the experimental results provided information on the sum of many particles with different properties. Behaviors of individual microparticles are expected to be different from each other depending on the sizes and shapes. In this research, we propose a new dynamics spectroscopy method for analyzing the photophysical and photochemical phenomena of a single microparticle with high accuracy and high sensitivity. This method is based on the optical resonance within the microsphere. Compared with the absorption loss caused by a single path through the particle, the change in the emission intensity was extremely amplified by the optical resonance in a spherical microparticle. Namely, the intracavity absorption spectroscopy is realized for the analysis of excited molecules in a microparticle. In addition, since a micrometer-sized short cavity has the ability to produce a picosecond lasing pulse with a single shot pumping, the ultrafast transient absorption process in the particle can be measured based on the pump-probe method. We succeeded in observing enhancement of spontaneous emission within polymer microspheres compared to that in free space, i.e., cavity quantum electrodynamic effect. Fluorescence decay rate increased with reducing the particle size, and the enhancement factor was determined to be -17 for a 2.4-μm latex sphere. The microspherical cavity enhancement of energy transfer processes caused by dipole-dipole interactions was also observed for aromatic-molecules-doped polymer microspheres.
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