Ab initio molecular dynamics and wavepacket dynamics of highly charged fullerene cations produced with intense near-infrared laser pulses

We theoretically investigated the stability of highly charged C60z+ cations produced with an ultrashort intense laser pulse of λ ∼ 1800 nm. We first review the results of our theoretical investigation of the stability of C60z+ cations and report that C60z+ cations up to z = 12 can be produced as a stable or quasistable (μs-order lifetime) intact parent cation. We next present the results of simulation as to how much vibrational energy is acquired by C60 or C60z+ through the interaction with an ultrashort intense pulse of λ = 1800 nm. This type of simulation was carried out by incorporating an ab initio classical molecular dynamics method into the framework of the time-dependent adiabatic state approach. The results indicate that large-amplitude vibration with energy of >20 eV is induced in the hg(1) mode of C60z+. C60 or C60z+ is mostly elongated along the field polarization direction, of which the motion can be described by using the time-dependent (TD) potential along the hg(1) coordinate. We also solved the corresponding TD Schrödinger equation to propagate the vibrational wavepacket on the TD potential. We found that the acquired vibrational energy is maximized at Tp ∼ Tvib/2, where Tp is the pulse length and Tvib is the vibrational period of the hg(1) mode. We show how the vibrational energy deposited in C60 can be controlled by changing the pulse separation of a train of three pulses. We finally discuss the structure and dissociation of C20z+.