Probing strong-field electron-nuclear dynamics of polyatomic molecules using proton motion

Proton ejection during Coulomb explosion is studied for several structure-related organic molecules (anthracene, anthraquinone, and octahydroanthracene) subjected to 8000.3em0exnm, 600.3em0exfs laser pulses at intensities from 0.50 to 4.0×10¹⁴0.3em0exW0.2em0excm^-2. The proton kinetic energy distributions are found to be markedly structure specific. The distributions are bimodal for anthracene and octahydroanthracene and trimodal for anthraquinone. Maximum (cutoff) energies of the distributions range from 500.3em0exeV for anthracene to 830.3em0exeV for anthraquinone. The low-energy mode (~100.3em0exeV) is most pronounced in octahydroanthracene. The dependence of the characteristic features of the distributions on the laser intensity provides insights into molecular specificity of such strong-field phenomena as (i) nonadiabatic charge localization and (ii) field-mediated restructuring of polyatomic molecules polarized by a strong laser field.