Carrier-envelope-phase-dependent dissociation of hydrogen

Abstract

We studied the dependence of dissociative ionization in H 2 on carrier-envelope phase (CEP) of few-cycle (6 fs) near-infrared laser pulses. For low-energy channels, we present the first experimental observation of the CEP dependence of combined dissociation yield (with protons emitted in both directions), as well as the highest degree of asymmetry reported to date (40%). The observed modulations in both asymmetry and combined yield could be understood in terms of interference between different n-photon dissociation pathways-n and (n + 1) photon channels for asymmetry, n and (n + 2) photon channels for yield-as suggested by the general theory of CEP effects (Roudnev and Esry 2007 Phys. Rev. Lett. 99 220406). The yield modulation is found to be π-periodic in CEP, with its phase strongly dependent on fragment kinetic energy (and reversing its sign within the studied energy range), indicating that the dissociation yield does not simply follow the CEP dependence of maximum electric field, as a naïve intuition might suggest. We also find that a positively chirped pulse can lead to a higher dissociation probability than a transformlimited pulse.

Carrier-Envelope Phase Control over Pathway Interference in Strong-Field Dissociation ofH2+

“…And, despite our ability to make cuts in the angular distribution to select the molecules that broke while nearly aligned with the laser polarization (limited by post-dissociation rotation [48]), intensity averaging apparently washes out any effect. In contrast, Xu et al observed modulation depths of up to 5% in the H + + H channel starting from an H 2 target, with 6 fs, 6 × 10 14 W/cm 2 pulses [12].…”

“…To this end, tailoring the electric field waveform of few-cycle laser pulses to control reactions and uncover the underlying physics has become a powerful tool [4][5][6]. It has been applied to the dissociative ionization of H 2 and its isotopologues [7][8][9][10][11][12] and has recently been extended to more complex diatomic molecules, such as CO [13][14][15], and to small polyatomic molecules [16,17].Conceptually, one of the most basic features of a fewcycle laser pulse to control is the carrier-envelope phase (CEP). When the laser's electric field is written as E(t) = E 0 (t) cos(ωt + φ), E 0 (t) is an envelope function, ω is the carrier angular frequency, and φ is the CEP.…”

Phase- and intensity-dependence of ultrafast dynamics in hydrocarbon molecules in few-cycle laser fields

“…A large part of previous work was performed on molecular hydrogen and molecular hydrogen ions (see e.g. [8][9][10][11][12][13][14][15][16][17][18]). …”

Subfemtosecond steering of hydrocarbon deprotonation through superposition of vibrational modes

“…Few-cycle waveforms with adjustable carrierenvelope-phase (CEP) have permitted control of charge localization in the ionization and dissociation of diatomic molecules on a subfemtosecond timescale [17][18][19][20][21] . The approach has also been successful in altering the yields of ionization and fragmentation in hydrocarbons 13 .…”