High-order harmonic generation of the cyclo[18]carbon molecule irradiated by circularly polarized laser pulse

High-order harmonic generation of the cyclo[18]carbon (C-18) molecule under few-cycle circularly polarized laser pulse is studied by time-dependent density functional theory. Compared with the harmonic emission of the ring molecule C6H6 having similar ionization potential, the C-18 molecule has higher efficiency and cutoff energy than C6H6 with the same laser field parameters. Further researches indicate that the harmonic efficiency and cutoff energy of the C-18 molecule increase gradually with the increase of the laser intensity of the driving laser or decrease of the wavelength, both are larger than those of the C6H6 molecule. Through the analysis of the time-dependent evolution of the electronic wave packets, it is also found that the higher efficiency of harmonic generation can be attributed to the larger spatial scale of the C-18 molecule, which leads to a greater chance for the ionized electrons from one atom to recombine with others of the parent molecule. Selecting the suitable driving laser pulse, it is demonstrated that high-order harmonic generation in the C-18 molecule has a wide range of applications in producing circularly polarized isolated attosecond pulse.

Automated summary

In this study, high-order harmonic generation of the cyclo[18]carbon (C-18) molecule under few-cycle circularly polarized laser pulse was investigated using time-dependent density functional theory. Compared to the harmonic emission of the ring molecule C6H6 with similar ionization potential, the C-18 molecule exhibits higher efficiency and cutoff energy under the same laser field parameters. Further research suggests that the harmonic efficiency and cutoff energy of the C-18 molecule increase gradually with the increase of laser intensity or decrease of the driving laser's wavelength, and they are both greater than those of the C6H6 molecule. Analysis of the time-dependent evolution of electronic wave packets reveals that the higher efficiency of harmonic generation in the C-18 molecule is attributed to its larger spatial scale, which provides a greater chance for ionized electrons from one atom to recombine with others of the parent molecule. Selecting the suitable driving laser pulse demonstrates that high-order harmonic generation in the C-18 molecule has a wide range of applications in producing circularly polarized isolated attosecond pulses.