Imaging intense-field dissociation of HeH+ as an analog for ionization

Although intense field ionization is generally regarded as well understood, there are still questions about how this understanding meshes with the dynamics predicted by the time-dependent Schr\"odinger equation (TDSE). We would like to answer these questions. In particular, we would like to study how the photoelectron spectrum develops over time. Is an ionized electron produced with zero kinetic energy as predicted by tunneling models? Can this question be answered in an experimentally verifiable way? As a first step, we use $\mathrm{HeH^{+}}$ as an analog to an atomic system and image the dissociating nuclear wavepacket, which allows us to use femtosecond rather than attosecond pulses. We use $\mathrm{HeH^{+}}$ because its nuclear TDSE is essentially identical to that of the electron in a one-electron atom, except that there is no Coulomb potential and the effective mass is much larger. We will study the time dependence of the above threshold dissociation of $\mathrm{HeH^{+}}$ in an intense field and discuss possible interpretations of our results within the context of intense field ionization theories.