Molecular resolvent-operator method: Electronic and nuclear dynamics in strong-field ionization

Abstract

We present an extension of the resolvent-operator method (ROM), originally designed for atomic systems, to extract differential photoelectron spectra (in photoelectron-and nuclear-kinetic energy) for diatomic molecules interacting with strong, ultrashort laser fields in the single active electron approximation. The method is applied to the study of H 2 + photodissociation and photoionization by femtosecond laser pulses in the XUV-IR frequency range. In particular, the method is tested (i) in the perturbative regime, for few-photon absorption and bound-bound electronic transitions, and (ii) in the strong-field regime, in which multiphoton absorption and tunneling are present. In the latter case, we show how the differential ROM allows one to track the transition between both regimes. We also analyze isotopic effects by comparing the dynamics of H 2 + and D 2 + ionization for different pulses.

Energy- and angle-resolved ionization ofH2+interacting with xuv subfemtosecond laser pulses

“…The molecular-resolvent-operator method was introduced in [28,29]. Here we will briefly review this method and explain how angular distributions can be extracted.…”

“…Usually, is the state after the end of the pulse, obtained by solving the TDSE. At sufficiently long times, i.e., when the two protons are far away from each other, the BO approximation becomes exact, so that the resolvent operator can be factorized onto an electronic part and a nuclear part [28,29], namely,…”

“…4 the calculated CKE spectra for all the cases under study. Note that in the monochromatic limit (infinite pulse duration) we expect to see energy conservation lines [28,29,37,38] satisfying the relationship Nω = E e + E N + D 2H + , where D 2H + = −E 0 = 0.597 a.u. is the threshold energy required to produce two protons at infinite internuclear distance, E 0 is the ground-state energy, E e and E N are the electronic and nuclear energies, respectively, and N is the number of absorbed photons.…”

“…Recently, we have proposed the use of the resolventoperator method (ROM), initially designed for atomic systems [26,27], to calculate correlated kinetic-energy (CKE) spectra (in electronic and nuclear energies) [28,29] of a low-dimensionality (1+1)D H 2 + molecule irradiated by xuv and ir fields [the (1+1)D notation indicates one degree of freedom for the electronic motion and another one for nuclear motion]. Here we extend this method (i) to treat the electronic motion in full dimensionality [three-dimensional (3D)] and (ii) to extract photoelectron angular distributions.…”

Dissociative ionization ofH2+: Few-cycle effect in the joint electron-ion energy spectrum

“…Only rotations are usually neglected, which is justified for short laser pulses. Despite the simplicity of H + 2 , its joint electron spectra (JES) for electrons and nuclei are intriguingly complex [3][4][5][6]. In fact, on top of the already complex features in photoelectron spectra from atoms [7] there is a nuclear degree of freedom added in H + 2 (or its isotopic sisters).…”