Energetics, Ionization, and Expansion Dynamics of Atomic Clusters Irradiated with Short Intense Vacuum-Ultraviolet Pulses

Kinetic equations are used to model the dynamics of Xe clusters irradiated with short, intense vacuum-ultraviolet pulses. Various cluster size and pulse fluences are considered. It is found that the highly charged ions observed in the experiments are mainly due to Coulomb explosion of the outer cluster shell. Ions within the cluster core predominantly recombine with plasma electrons, forming a large fraction of neutral atoms. To our knowledge, our model is the first and only one that gives an accurate description of all of the experimental data collected from atomic clusters at 100 nm photon wavelength.

Figure 1

Ion fractions, $N_i/N$, within the irradiated clusters estimated for four various cluster sizes. $N_i$ denotes here the number of ${\mathrm{Xe}}^{+i}$ ions, and $N$ is the total number of ions. We show also: (e) average charge, $Z$, created within the irradiated cluster, and (f) average energy absorbed per ion, $E$, as a function of the cluster radius, $R$. Experimental data, model predictions for clusters placed in the center of the focussed beam and predictions integrated over the Gaussian spatial pulse profile are shown.

Figure 2

Ion fractions, $N_i/N$, within the irradiated xenon clusters ($N_{\mathrm{atoms}}=2500$). These clusters were irradiated with rectangular shaped pulses of four various fluences. We show also: (e) average charge, $Z$, created within the irradiated xenon cluster, and (f) average energy absorbed per ion, $E$, as a function of the pulse fluence, $F$. Other notations are as in Fig. 1.