Controlling H3+ Formation From Ethane Using Shaped Ultrafast Laser Pulses

Abstract

An adaptive learning algorithm coupled with 3D momentum-based feedback is used to identify intense laser pulse shapes that control H3+ formation from ethane. Specifically, we controlled the ratio of D2H+ to D3+ produced from the D3C-CH3 isotopologue of ethane, which selects between trihydrogen cations formed from atoms on one or both sides of ethane. We are able to modify the D2H+:D3+ 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 D2H+ and D3+ production rates are monitored. The optimized pulse is observed to influence the yield, kinetic energy release, and angular distribution of the D2H+ ions while the D3+ ion dynamics remain relatively stable. We subsequently conducted COLTRIMS experiments on C2D6 to complement the velocity map imaging data obtained during the control experiments and measured the branching ratio of two-body double ionization. Two-body D3+ + C2D3+ is the dominant final channel containing D3+ ions, although the three-body D + D3+ + C2D2+ final state is also observed.

Strong-field ionization of CH3Cl: proton migration and association

“…To estimate the amount of chirp, we have calculated the group delay dispersion for SF11 of different thicknesses, which are displayed in Table 2. The fragmentation of atoms [56][57][58] and polyatomic molecules [59][60][61] has been found to be strongly affected by chirp and its control using shaped pulses has been demonstrated in earlier experiments. In addition, the laser pulse duration affects the ultrafast excited state dynamics of the parent ion and its subsequent fragmentation.…”

What is the Mechanism of H3+ Formation from Cyclopropane?

“…Ultrafast dissociative ionization methods allow researchers to explore the mechanism of formation of fragment ions, including H 3 + , by irradiating molecules with powerful femtosecond laser pulses. − It must be noted that the unimolecular reaction that leads to H 3 + formation requires the breaking of three bonds and formation of three new H–H bonds, which often involves significant deformation of the molecular geometry. Therefore, studying the mechanism of H 3 + formation from ionized hydrocarbons deepens our understanding of such complex ultrafast molecular dynamics and inspires approaches to control them. − …”

Dissociative ionization and Coulomb explosion of CH4 in two-color asymmetric intense laser fields

“…In order to explore the pulse shape to maximize a certain reaction channel, machine learning techniques based on, e.g., genetic algorithm, have been adopted and successfully applied to selective bond breaking and bond rearrangement of small molecules. [1][2][3][4][5][6][7] The carrier-envelope-phase (CEP) locked few-cycle pulse 8,9 utilizes the CEP as a tuning knob to manipulate the electric field waveform, which varies by the phase between the carrier wave and the envelope. The CEP-locked few-cycle pulses are utilized to control electron localization of H 2 + , 10,11 and D 2 +11-14 during the dissociative ionization H 2 -H + + H + e À (D 2 -D + + D + e À ).…”

“…Fig.5(a) Total kinetic energy release (KER) spectra for the dissociative ionization pathway (ii). (b) KER integrated asymmetry parameter, A(f) in eqn(7), for H + in the kinetic energy ranges 0 r E KER r 0.2 eV (open circles) and 0.2 r E KER r 2 eV (filled circles). The statistical uncertainties are smaller than the size of the markers.…”