Multiple ionization of CH3I clusters by nanosecond laser: Electron energy distribution and formation mechanism of multiply charged ions

To understand the production mechanisms for multiply charged ions Cq+ (q = 2–3) and Iq+ (q = 2–4), the kinetic energy of released electron was measured for understanding the interaction of nanosecond laser with CH3I cluster. The mean electron energy increased from 19 to 33 eV as the laser intensity was raised from 2.9 × 109 to 4.7 × 1010 W/cm2. The evolution of the mean electron energy as a function of laser intensity was similar to that of multiply charged ions, which indicated that electron impact ionization played an important role in the formation of Cq+ (q = 2–3) and Iq+ (q = 2–4). Moreover, the formation of more ionized sites would lead to the cluster splitting, which is disadvantageous for the multiply charged ion production.