Time-of-flight distributions of sputtered Au atoms have been measured under 4 ke V ${\mathrm{I}}^{+}$ and 8 keV ${\mathrm{I}}_2^{+}$ impact. The results show that a developing thermal spike contributes to the sputtering yield. It is higher under ${\mathrm{I}}_2^{+}$ bombardment but the measured temperature obtained from Maxwell-Boltzmann fits is lower, suggesting a lower effective surface binding energy $U_0$ for ${\mathrm{I}}_2^{+}$ bombardment. A correlation between spike temperatures and $U_0$ is discussed.

• Received 9 November 1987

DOI:https://doi.org/10.1103/PhysRevLett.61.1392