Exploring the formation of trihydrogen monocations from ethane using shaped ultrafast laser pulses*

COLTRIMS measurements of ethane molecules exposed to 23-fs, 1$\times$10$^{14}$-W/cm$^2$, 780-nm laser pulses are used to obtain the two-body fragmentation branching ratios, kinetic energy release, and angular dependence of the resulting photofragments with an emphasis on examining D$_3^+$ formation. D$_3^+$ + C$_2$D$_3^+$ is the most likely two-body double ionization channel. These measurements are contrasted with velocity map imaging studies of D$_3^+$ and D$_2$H$^+$ production in interactions between shaped ultrafast laser pulses and the D$_3$C-CH$_3$ isotopologue of ethane, which selects between trihydrogen monocations formed from atoms on one or both sides of ethane. When an adaptive learning algorithm supplied with 3D momentum-based feedback is used to identify intense laser pulse shapes that enhance the D$_2$H$^+$/D$_3^+$ ratio from D$_3$C-CH$_3$, the observed D$_2$H$^+$ angular distribution is altered significantly.