Theoretical investigation of the Freeman resonance in the dissociative ionization of $H_2+$

Abstract

The dissociative ionization of $H_2^{+}$ in linearly polarized, 400 nm laser pulses is simulated by solving a three-particle time-dependent Schrödinger equation in full dimensionality. The joint energy spectra (JES) are computed for ${\cos }^8$ and flat-top envelopes using the time-dependent surface flux (tSurff) methods. In JES, the energy sharing $n$ photon energies $\omega$ of nuclear kinetic energy release (KER) $E_N$ and electronic KER $E_e$ are well represented by $E_N+E_e=n\omega -U_p+E_0$ for ${\cos }^8$ pulses, but satisfy $E_N+E_e=n\omega +E_0$ for flat-top envelope, exposing a deviation of the ponderomotive energy $U_p$, which has been observed in experiments, where $E_0$ is the ground energy of $H_2^{+}$. The analysis of the wavefunction for electrons and protons after the pulse are presented, where we find $U_p$ is absorbed by the Freeman resonances between two excited ungerade states.

arXiv commentarXiv admin note: text overlap with arXiv:2007.10179

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