Ionization and dissociation of alkanes in few-cycle laser fields

Abstract

We experimentally studied the ionization and dissociation of methane, ethane, and propane in strong $8\phantom{\rule{0.3em}{0ex}}\mathrm{fs}$ laser fields at an intensity of several ${10}^{14}\phantom{\rule{0.3em}{0ex}}\mathrm{W}∕{\mathrm{cm}}^{2}$. Strong parent ions and abundant fragmental ions were observed for all three of these kinds of molecules. Our observations indicated that these molecules were first ionized under strong ultrashort laser fields and electron-ion pairs were produced. Driven by the remaining laser oscillating electric field, the parent ion and the correlated electron collided with each other. Depending on the electron-ion impact energy, the parent ion was excited to a dissociated state or a doubly charged state. The experimentally observed fragmental ions resulted from the recollision-induced dissociation of the singly charged parent ion or the Coulomb explosion of the doubly charged parent ion.