Ionization and fragmentation of C60 with sub-50 fs laser pulses

Abstract

Gas-phase C60 photoionization and photofragmentation experiments were performed using a sub-50 fs Ti Sapphire laser system and reflectron time-of-flight (RETOF) mass spectrometer. The dependence of the C60+ and C602+ signals on the laser intensity for the fundamental (795 nm) and second harmonic (ca. 400 nm) has been determined. For low laser intensities, before the onset of fragmentation, single ionization is a direct multiphoton process. Double ionization is a sequential process in which C602+ originates from already singly ionized fullerenes. At laser intensities beyond the onset of C602+ there is considerable metastable fragmentation indicating a strong coupling of electronic excitation energy into vibrational degrees of freedom that appears to be in competition with multiple ionization.

Recollision during the High Laser Intensity Ionization ofC60

“…In addition, at longer wavelengths recollision is more sensitive to laser polarization and maximum electron recollision energies (3.2 U p )o f . The spectrum at 800 nm is similar to that reported previously [13].…”

“…The effect of using infrared radiation in C 60 is shown in Fig. 1 where our results at 1500 nm are compared to 800 nm [13]. Ionization at long wavelengths is simplified, fragmentation is more controlled, and highly charged C 60 cations up to C 12 60 are generated [11].…”

Internal Laser-Induced Dipole Force at Work inC60Molecule

“…In contrast, at 800 nm the maximum charge state reached using pulses down to 35 fs is C 3 60 [15], while at 25 fs C 5 60 is observed [16]. Figure 1 shows the mass spectrum obtained at 10 production is overwhelming [ Fig.…”

Coherent Electronic Wave Packet Motion inC60Controlled by the Waveform and Polarization of Few-Cycle Laser Fields

“…Angularly resolved photoionization by ultrashort laser pulses has been advocated for probing the electronic dynamics before the onset of significant nuclear motion (see, e.g., [27][28][29][30][31] [36,37], and efficient high-harmonic generation [38][39][40]. The ionization and fragmentation of C 60 have been investigated extensively in the past (see, e.g., [35,[41][42][43][44][45][46][47]). C 60 is very stable and is one of the few molecular systems for which the ionization energy is smaller than the lowest fragmentation threshold.…”