Carrier-envelope phase control over pathway interference in strong-field dissociation of H$_2^+$

TL;DR

This study demonstrates control over molecular dissociation pathways of H$_2^+$ using carrier-envelope phase in ultrafast laser pulses, revealing interference effects that depend on photon number pathways and matching theoretical predictions.

Contribution

It provides the first experimental observation of carrier-envelope-phase-dependent pathway interference in H$_2^+$ dissociation, enabling quantitative comparison with ab initio theory.

Findings

Asymmetries in fragment emission depend on CEP.

Interference of photon pathways influences kinetic energy releases.

Results agree with strong-field coherent control theory.

Abstract

The dissociation of an H$_2^+$ molecular-ion beam by linearly polarized, carrier-envelope-phase-tagged 5 fs pulses at 4$\times10^{14} $W/cm$^2$ with a central wavelength of 730 nm was studied using a coincidence 3D momentum imaging technique. Carrier-envelope-phase-dependent asymmetries in the emission direction of H$^+$ fragments relative to the laser polarization were observed. These asymmetries are caused by interference of odd and even photon number pathways, where net-zero photon and 1-photon interference predominantly contributes at H$^+$+H kinetic energy releases of 0.2 -- 0.45 eV, and net-2-photon and 1-photon interference contributes at 1.65 -- 1.9 eV. These measurements of the benchmark H$_2^+$ molecule offer the distinct advantage that they can be quantitatively compared with \textit{ab initio} theory to confirm our understanding of strong-field coherent control via the carrier-envelope phase.