高速粒子による衝突活性化

抄録

Collisional activation of the matter induced by the bombardment of the fast particle is summarized. The particle with the velocity higher than the Bohr velocity (transit time through 5A shorter than 2.5×10^-16s) experiences the electronic stopping power when it passes through the matter and induces dense electronic excitations and ionizations which results in the heavy sputtering of the matter. This kind of activation is usefully applied in the PDMS. When the particle velocity becomes lower than the Bohr velocity, the energy is mainly deposited to the matter by the nuclear stopping power, i.e., energy loss is governed by the screened Coulombic collisions of the atoms giving rise to the momentum transfer to the target nuclei. When the transit time of the particle through 5A is between 2.5×10^-16-10^-14 s, the electronic excitation and ionization take place by the collision. These phenomena are fully utilized in the FAB/SIMS and CID techniques. With the transit time in the range of 10^-14-2.5×10^-13s, the velocity is not high enough for the electronic excitation and the particle loses its energy mainly by the vibrational and phonon excitation of the target. This range of the velocity corresponds to that of the massive cluster impact ionization. With the velocity equal to or lower than 2.5×10^-13s, the energy of the incident particle is consumed mainly by the phonon excitation and the collision results in the modest heating of the colliding interface between the projectile and the target. This range of the velocity is successfully used in the ionized cluster beam technique developed by Takagi of the Kyoto University.