Saturated Ionization of Fullerenes in Intense Laser Fields

We investigate the ionization of icosahedral fullerenes (${\mathrm{C}}_{20}$, ${\mathrm{C}}_{60}$, ${\mathrm{C}}_{80}$, and ${\mathrm{C}}_{180}$) in an intense laser pulse using the $S$-matrix theory. The results obtained are in excellent agreement with the recent observations of unexpectedly high saturation intensities of the Buckminster fullerene and its multiply charged ions. Our analysis strongly suggests that the related phenomenon of suppressed ionization of these complex fullerenes is due to the finite cage size and the “multislit” interference effect between partial waves emitted from the different nuclei rather than to a dynamical multielectron polarization effect.

Figure 1

Comparison of the theoretical predictions for the saturation intensities for the first nine charge states of ${\mathrm{C}}_{60}$ (open circles) with the experimental data (solid squares, [3]) at a laser wavelength of 1500 nm and a pulse duration of 70 fs.

Figure 2

Saturation intensities of the first charge state ${\mathrm{C}}_{60}^{+}$ as a function of wavelength at a pulse duration of 70 fs.

Figure 3

(a) ${\mathrm{C}}_{60}^{+}$ ion yields as a function of peak intensity at 800 nm (dashed line) and 1500 nm (solid line) wavelength. (b) Comparison of the theoretical predictions (lines) for the ion yields of ${\mathrm{C}}_{60}^{3+}$ and ${\mathrm{C}}_{60}^{4+}$ with the experiment data (open squares, [15]) at 1500 nm. Pulse duration: 70 fs.

Figure 4

Comparison of the saturation intensities for ionization of the four smallest fullerenes ${\mathrm{C}}_{20}$, ${\mathrm{C}}_{60}$, ${\mathrm{C}}_{80}$, and ${\mathrm{C}}_{180}$ having $I_h$ symmetry: full calculations (solid circles), zero-radius approximation (solid triangles), incoherent zero-radius approximation (solid diamonds), and atomic tunneling predictions (open squares). Laser parameters as in Fig. 1.