Coulomb Explosion in Nanosecond Laser Fields.

We report experimental observations of Coulomb explosion using a nanosecond laser at 532 nm with intensities less than 1012 W/cm2. We observe multiply charged atomic ions Arn+ (1 ≤ n ≤ 7) and Cn+ (1 ≤ n ≤ 4) from argon clusters doped with molecules containing aromatic chromophores. The yield of Arn+ depends on the size of the cluster, the number density, and the photostability of the dopant. We propose that resonant absorption of ArN+ achieves a high degree of ionization, and the highly positively charged cluster has the capability to strip electrons from the evaporating Ar+ on the surface of the cluster prior to Coulomb explosion, forming Arn+.