A detailed and precise study of the ionization rates of H⁺₂in intense laser fields

Abstract

Ionization of the hydrogen molecular ion under linearly polarized intense laser fields is simulated by direct solution of the fixed-nuclei time-dependent Schrödinger equation for λ = 790 nm and I = 1 × 1014 W cm−2. Different adaptive grids used in this study produced very similar results. The results are in agreement with, and thus support, the results of recent calculations carried out by other researchers. Detailed structure of the ionization rates is presented which has not been reported so far in the literature. The use of the virtual detector method resulted in more details of the ionization rates of the hydrogen ion molecule and hydrogen atom. This method especially allowed a simultaneous detection of the parallel and perpendicular components of the ionization rates.

<title>Fragmentation of molecules studied with laser-induced Coulomb explosion imaging and femtosecond pump-probe experiments</title>

“…Using a combination of the "reaction microscope" spectrometer, which allows coincident detection of several charged particles with excellent momentum resolution, and a pump-probe setup providing two identical 25 fs pulses with variable delay at sub-fs accuracy, we are able to resolve in space and time the motion of two different dissociating wave packets produced by net absorption of one or two photons. We provide experimental evidences of the existence of a second maximum in the R-dependent ionization probability for H 2 + , which was predicted in several previous theoretical studies [12][13][14][15] . Finally, we demonstrate that by using an interferometrically stable pumpprobe setup which allows control of the electric field shape in the region of overlapping pulses, a clear pump probe experiment can be carried out even in this regime by selecting only those delays for which both pulses interfere destructively.…”

“…It might most likely be explained by considering the Rdependence of the ionization rate of dissociating H 2 + molecular ions. Several theoretical studies [12][13][14][15] have predicted the existence of a second maximum in the ionization probability around R = 10 a.u. (E C = 1.36 eV per proton), well beyond the region corresponding to the CREI-peak observed in single pulse measurements (2 -4 eV).…”

“…The former mechanism becomes more complex in the molecular case since the ionisation potential of the molecular ion depends on the internuclear separation R. In addition, at intermediate R an even stronger enhancement of the field ionisation rates is observed due to the interaction of the 1sσ g and 2pσ u states, which causes an oscillating localisation of the electron cloud at one of the nuclei. This effect of charge resonance enhanced ionisation (CREI) [12][13][14][15] gives the highest ionisation probabilities for H 2 + in a range of internuclear distance from 4 to 7 a.u. and 9 -12 a.u., corresponding to a KER per proton of 2 to 4 eV and 1 -1.5 eV, respectively.…”

Detailed instantaneous ionization rate ofH2+in an intense laser field

“…with the decrease in the Keldysh parameter) [22]. The virtual detector method made it possible to define and distinguish ionization rates and outgoing norms from different boundaries which can be used to study details of the dynamics of the spatial evolution of the electron wavefunction [18]. Moreover, based on the instantaneous ionization rates (IIR), details of the time-dependent behavior of the system following the variations of the laser field can be extracted and used in the interpretation of the enhanced ionization rates [28].…”

Static Coherent States Method: One- and Two-Electron Laser-Induced Systems with Classical Nuclear Dynamics

“…This approach is implementable for simulating systems with a limited number of particles in a limited region of momentum or coordinate space. There are different TDSE approaches for simulating the electron dynamics in an atomic or molecular laser-induced system in one, two, or three (full) coordinate (or momentum) dimensions [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. Some of the TDSE approaches treat the nuclei in the laser-induced system dynamically using classical or quantum mechanics.…”