Theoretical investigation of the stability of highly charged C60 molecules produced with intense near-infrared laser pulses

We theoretically investigated the stability of highly charged C-60(z+) cations produced from C-60 with an ultrashort intense laser pulse of lambda similar to 1800 nm. We first calculated the equilibrium structures and vibrational frequencies of C-60(z+) as well as C-60. We then calculated key energies relevant to dissociation of C-60(z+), such as the excess vibrational energy acquired upon sudden tunnel ionization from C-60. By comparing the magnitudes of the calculated energies, we found that C-60(z+) cations up to z similar to 12 can be produced as a stable or quasistable (microsecond-order lifetime) intact parent cation, in agreement with the recent experimental report by V. R. Bhardwaj [Phys. Rev. Lett. 93, 043001 (2004)] that almost only intact parent C-60(z+) cations up to z=12 are detected by a mass spectrometer. The results of Rice-Ramsperger-Kassel-Marcus calculation suggest that the lifetime of C-60(z+) drastically decreases by ten orders of magnitude as z increases from z=11 to z=13. Using the time-dependent adiabatic state approach, we also investigated the vibrational excitation of C-60 and C-60(z+) by an intense near-infrared pulse. The results indicate that large-amplitude vibration with energy of > 10 eV is induced in the delocalized h(g)(1)-like mode of C-60(z+).