Figure 1

(a) Harmonic generations in ${\mathrm{C}}_{60}$. The laser energy is 0.4 eV, pulse duration is 32 laser cycles, and field strength is $0.02\mathrm{eV}/\AA$. Peak $a$ results from the lattice vibration. Peaks $b$, $c$, and $d$ are at the 1st, third, and seventh orders, respectively. Above the 7th order, harmonics mainly result from the intrinsic electronic excitations. (b) The emitted photon energy versus the incident energy. The circles, diamonds, and squares denote peak $e$, the third harmonic, and the first harmonic, respectively. (c) Assignment of peaks from $d$ to $m$ (see letters below arrows) to their respective transitions (double-arrow lines). The $H_u$ (HOMO) is at $-1.6158\mathrm{eV}$ and the $T_{1u}$ (LUMO) is at 0.5255 eV.Reuse & Permissions

Figure 2

(a) Efficiency of generating peak $j$ as a function of the laser frequency. ${\ddot{d}}_j$ and ${\ddot{d}}_{\mathrm{base}}$ are the amplitudes of peak $j$ and the background baseline, respectively. The error bars represent the difference between two baselines before and after peak $j$. The pulse duration and field strength are same as those in Fig. 1. (b) Intensity dependence of harmonics $d$ and $m$. The power of the high harmonic $m$ is lower than its order. The pulse duration and frequency are same as those in Fig. 1.Reuse & Permissions