Ultrafast double hydrogen migration in ethanol*

Hydrogen migration is ubiquitous in nature. Strong-field induced single hydrogen migration in small hydrocarbons has been studied with a variety of light sources, and, for acetylene and allene, has even been controlled via the carrier-envelope phase of a laser pulse. Previous strong field laser experiments have also shown that for more complex targets, such as ethanol, two hydrogen atoms can migrate, producing the H$_{\mathrm{3}}$O$^{\mathrm{+}}$ hydronium ion. Here we use 35 fs, 790 nm, mid-10$^{\mathrm{14\thinspace }}$W/cm$^{\mathrm{2}}$ laser pulses, to induce double hydrogen migration in ethanol and record the resulting ionic fragments with a cold-target recoil ion momentum spectrometer (COLTRIMS) apparatus. Following Coulomb explosion, the molecules fragment into many channels, including the coincident H$_{\mathrm{3}}$O$^{\mathrm{+}} \quad +$ C$_{\mathrm{2}}$H$_{\mathrm{3}}^{\mathrm{+\thinspace }}$channel of interest. Theoretical support indicates that the first hydrogen comes from the terminal carbon, and the second comes from the adjacent carbon, occurring on a 10's to 100's of fs timescale.