Absolute Ionization Rates of Multielectron Transition Metal Atoms in Strong Infrared Laser Fields

We compare strong-field ionization probabilities of N 2 and F 2 molecules using time-dependent density functional theory calculations. Accurate nuclear potentials and ground vibrational wave functions are incorporated into our study. For both molecules, the effect of molecular vibration is small, while that of the molecular orientation is significant. When compared to the ionization probability of a molecule at the equilibrium geometry, we estimate the effect of the ground state vibration to be within 3% for N 2 and within 6% for F 2 in the intensity range from 1 to 5 × 10 14 W/cm 2 . The molecular-orientation-dependent ionization probabilities for both molecules at various intensities are presented. They are strongly dependent on the laser intensity, and the anisotropy diminishes when the laser intensity is high. For laser intensities of 1.6 and 2.2 × 10 14 W/cm 2 we find ionization probability ratios of 5.9 and 4.3, respectively, for the parallel versus perpendicular orientation of N 2 . This is reasonably consistent with experimental measurements. For randomly oriented molecules, the ratio of the probabilities for N 2 and F 2 increases from about 1 at 10 14 W/cm 2 to 2 at 4 × 10 14 W/cm 2 , which agrees well with experimental results.

Section: Introductionmentioning

confidence: 99%

Comparison of the strong-field ionization ofN2andF2: A time-dependent density-functional-theory study

Chu

McIntyre

2011

“…As such, the ionization is a tunneling process often modeled by Ammosov-Delone-Krainov (ADK) theory [6]. As a single active electron (SAE) theory, ADK predicts the TI rates of inert gases reasonably well [7], while it overestimates those rates for some other atoms and molecules [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

“…Transition-metal atoms and their ions in different oxidation states form coordination complexes of chemical importance. In short-wavelength IR lasers, the reduction of the ionization yields for the transition-metal atoms V, Ni, Pd, Ta, and Nb is equivalent to an increase of the ionization potential by a few eV [10,11]. Multielectron effects are considered the cause of the discrepancy [12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%

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Suppressed and enhanced tunneling ionization of transition-metal atoms and cations: A time-dependent density-functional-theory study on nickel

Chu

Groenenboom

2020

We study the tunneling ionization (TI) of Ni, Ni + , and Ni 2+ with a time-dependent density-functional-theory method and reproduce the puzzling suppression of the TI of Ni and Ni + and the enhancement of TI in Ni 2+ . Numerical results reveal that for all three species the electron tunnels from a 4s orbital; that is, excitation precedes tunneling for both of the cations, for which the highest orbitals are 3d. The effective radial potentials for the d orbitals have a centrifugal barrier, while there is no such barrier for the s orbitals. At the classical turning point for the 3d orbital, the 3d to 4s excitation energy is lower than the centrifugal potential for the d orbitals. Two factors of opposite nature are identified in this work. On the one hand, electrons moving away from the nucleus in the intense laser fields induce an attractive potential that effectively lowers the energy level and thus suppresses tunneling. Excitation, on the other hand, has the opposite effect and enhances tunneling. The energy gap between 4s and 3d is small for Ni + and therefore suppression wins. As the charge of the cation increases, the excitation energy becomes much greater, and for Ni 2+ enhancement dominates. Based on a similar analysis, we expect enhanced TI for several transition-metal cations of charge 2 and higher.

“…Though the suppressing effect of the Stark shift on the tunneling rate has been investigated both in the tunneling regime [21][22][23] and barrier-suppression regime [24], the effect of polarization on the tunneling process and its underlying picture have not been fully explored yet. On the other hand, the polarization effect may be more prominent for complex atoms and molecules [25][26][27]. Therefore, the role of * wdli@sxu.edu.cn † chen_jing@iapcm.ac.cn the polarization effect in the tunneling process deserves to be investigated carefully.…”

Section: Introductionmentioning

confidence: 99%

Suppressing the effect of polarization in tunneling ionization of the hydrogen atom

Hao

Zhang

et al. 2013

An analytic expression for the tunneling ionization rate of hydrogen atom in a static electric field after taking into account higher-order perturbation of the external field is derived. The formula shows a suppression effect on the ionization rate compared with the conventional tunneling formula and well agrees with the result of numerical solution of time-dependent Schrödinger equation. Our analysis shows that the suppression effect can be attributed to the polarization of the initial wave function induced by the external electric field.