Vicinage effect on the yield of convoy electrons emitted from thin carbon foil induced by the penetration of 3.5-MeV/atom <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mi mathvariant="normal">C</mml:mi><mml:mi>n</mml:mi><

We investigated the convoy electron yields resulting from bombardments of amorphous carbon foils with 3.5-MeV/atom ${\mathrm{C}}_{n}^{+}$ ($n=1$--3) cluster ions. The target thickness ranged from 3.0 to $29.7\phantom{\rule{0.28em}{0ex}}\textmu{}\mathrm{g}/{\mathrm{cm}}^{2}$. A detailed analysis of the thickness dependence revealed that for bombardments with ${\mathrm{C}}_{2}^{+}$ and ${\mathrm{C}}_{3}^{+}$ ions, the convoy electron yield per atom, ${Y}_{n}/n$, decreases with increasing target thickness and ultimately reaches an asymptotic value. The asymptotic value showed clear proportionality to the cluster size, $n$, indicating the presence of positive vicinity effects of ${Y}_{n}\ensuremath{\propto}{n}^{2}$. We found that the escape length of the convoy electrons for ${\mathrm{C}}_{3}^{+}$ and ${\mathrm{C}}_{2}^{+}$ is much longer than that of the ${\mathrm{C}}^{+}$ bombardment. The present result suggests that the enhancement of the escape length could be the origin of this vicinage effect on the convoy electron yield.