Fragmentation and Ionization Dynamics ofC60in Elliptically Polarized Femtosecond Laser Fields

Abstract

Ionization and fragmentation of C60 fullerenes is studied in elliptically polarized, intense fs laser fields at 797 nm [I=(0.5-4.3)x10;{14} W cm;{-2}] and contrasted with Xe+, utilizing time-of-flight mass spectrometry. Very pronounced changes of parent and fragment ion yield as a function of ellipticity are observed. At lower intensities reduction of the ion yield for circular polarization establishes a coherent two-photon process connected with the key role of the LUMO+1(t_{1g}) "doorway state" and multielectron dynamics. Comparison with the behavior at 399 nm corroborates this finding. At high intensities enhanced fragmentation is observed which is tentatively attributed to returning loops of electron trajectories by the combined action of the C60+ field and the circular laser field.

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.…”

“…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.…”

Chirp and polarization control of femtosecond molecular fragmentation

“…Study of control of photo-fragmentation and photochemical reactions with different parameters or 'control knobs' of the interacting laser pulse, such as, the temporal shape [1][2][3][4], frequency content [5], intensity [6,7], polarization [8,9], etc., is of great interest due to its diverse applications ranging from fabrication of gene chips, microelectronic lithography or photodynamic therapy 1 to even quantum information processing [10,11]. Femtosecond laser pulse photo-fragmentation experiments with varying laser polarization or instantaneous phase characteristics (chirp) have evolved polarization and chirp as the two important 'control knobs' affecting the fragmentation under the fixed conditions of excitation wavelength, laser intensity, and beam focusing geometry [3,8,9,12,13].…”

“…Femtosecond laser pulse photo-fragmentation experiments with varying laser polarization or instantaneous phase characteristics (chirp) have evolved polarization and chirp as the two important 'control knobs' affecting the fragmentation under the fixed conditions of excitation wavelength, laser intensity, and beam focusing geometry [3,8,9,12,13].…”

“…The fragmentation processes in polyatomic molecules induced by intense laser field often exhibit sensitive dependence on either the chirp [3,12,13] or the polarization [8,9,14] of the laser field. Depending on the change in the sign of the chirped laser pulses, fragmentation could be either enhanced or suppressed.…”