Vicinage effect on secondary-electron emission from amorphous carbon foils induced by swift C ions

高速Cイオンによって誘起された非晶質炭素膜からの二次電子放出に対する近接効果

鳴海 一雅; 高橋 康之*; 千葉 敦也; 齋藤 勇一; 山田 圭介; 石川 法人   ; 須貝 宏行; 前田 佳均

Narumi, Kazumasa; Takahashi, Yasuyuki*; Chiba, Atsuya; Saito, Yuichi; Yamada, Keisuke; Ishikawa, Norito; Sugai, Hiroyuki; Maeda, Yoshihito

We have investigated the vicinage effect on secondary-electron (SE) emission by observing the SE yield emitted from an amorphous carbon foil bombarded with swift C ions. We have observed for the first time that the vicinage effect on the SE yield in the forward direction induced by 62.5-keV/u C ions disappears for thick foils (61-150 g/cm). In addition, it has been observed that the SE yield in the forward direction is larger when the final polar angle defined by the internuclear vector connecting the two fragment ions emerging downstream from the foil relative to the incident beam direction is close to 0 than when it is close to 90 for a pair of outgoing C- C fragment ions from the 4-g/cm foil; no clear difference was observed for the other thicker foils. Evaluating two threshold internuclear distances to characterize the interaction lengths based on the above observations leads to the conclusion that a transport process of scattered electrons is very important for the vicinage effect as well as a production process of scattered electrons by a projectile. The origin of the vicinage effect on the SE yield will be discussed based on the present results.