The high harmonic generation of heteronuclear hydrogen molecular ions in few-cycle infrared strong laser fields is studied by numerically simulating the time-dependent Schrödinger equation. By reversing the carrier envelope phase of the few-cycle laser pulse, the electron dynamics is reversed as well. However, due to the different nuclear masses, two nuclei move with different repulsive speeds, which makes the rescattering processes not identical when the carrier envelope phase shifts by $\pi$. The different rescattering processes lead to distinct harmonic spectra in the cutoff region. The mass-dependent harmonic spectrum offers a view angle to diagnose the isotope dynamics in molecules with unprecedent high time and spatial resolutions.

• Received 14 August 2018

DOI:https://doi.org/10.1103/PhysRevA.98.053409