Controlling H3+ Formation From Ethane Using Shaped Ultrafast Laser Pulses

An adaptive learning algorithm coupled with 3D momentum-based feedback is used to identify intense laser pulse shapes that control H$_3^+$ formation from ethane. Specifically, we controlled the ratio of D$_2$H$^+$ to D$_3^+$ produced from the D$_3$C-CH$_3$ isotopologue of ethane, which selects between trihydrogen cations formed from atoms on one or both sides of ethane. We are able to modify the D$_2$H$^+$:D$_3^+$ ratio by a factor of up to three. In addition, two-dimensional scans of linear chirp and third-order dispersion are conducted for a few fourth-order dispersion values while the D$_2$H$^+$ and D$_3^+$ production rates are monitored. The optimized pulse is observed to influence the yield, kinetic energy release, and angular distribution of the D$_2$H$^+$ ions while the D$_3^+$ ion dynamics remain relatively stable. We subsequently conducted COLTRIMS experiments on C$_2$D$_6$ to complement the velocity map imaging data obtained during the control experiments and measured the branching ratio of two-body double ionization. Two-body D$_3^+$ + C$_2$D$_3^+$ is the dominant final channel containing D$_3^+$ ions, although the three-body D + D$_3^+$ + C$_2$D$_2^+$ final state is also observed.