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Quantum Science and Engineering

'Quantum Beams' like charged particles (ion, electron, cluster) and photons (laser, X-rays) can easily generate various extreme environmental conditions (high temperature, high pressure, high energy-density) in a nanometer-sized area of matter during a very short time less than a picosecond. Quantum beams are, thus, highly effective probes to study the nanoscaled quantum mechanical world, providing sophisticated new techniques to create novel materials in many high-technology-based industrial fields such as semiconductor, biomolecule and aerospace researches. Definitely important, here, is to know correctly the nature of atoms and molecules revealing various quantum phenomena under the extreme conditions. We study these quantum phenomena systematically in order to achieve precise understanding, find new principles of physics and explore new interdisciplinary research fields leading to the establishment of safe and recycling-based human society.

Research Topics

Ionization and fragmentation of C60 induced by fast heavy ions

A spherical shaped C60 fullerene of 0.7nm in diameter, consisting of tightly bonded 60 carbon atoms, is a very stable new molecule found recently. During collisions with fast heavy ions, C60 is highly excited and eventually decayed emitting many electrons and small fragment ions. By measuring these fragment ions with a time-of-flight coincidence method, quantitative understanding is achieved about anti-radiation stability and mechanisms leading to electronic excitations and how these excitations evolve with emission of secondary particles.

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Figure 1:Fragment ions produced from C60 in collisions with fast carbon ions.

Ion-irradiation-induced polymerization of C60 thin film, energy and angular distribution of secondary fullerene ions

C60 thin film formed on a Si(111) substrate is known to have a fcc crystal structure via weak van der Waals force. The bond-strength of a film is in practice too weak to be used as a new materials. As a novel technique to overcome this problem, we employ the ion-irradiation method using various slow-to-fast ions.Also, we study a sputtering process resulting in the formation of large fullerenes such as C64 and (C60)2. to understand the mechanism in detail, we investigate energy and angular distribution of these fullereren ions.

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Figure 2:Angular and energy distribution of secondary ions produced from a C60 thin film bombarded by 4MeV Si ions.