Charge-Resonance Dynamics and Backscattering Effects in Enhanced Ionization of H<sub>2</sub><sup>+</sup> in intense, long-wavelength fields
POSTER
Abstract
When a diatomic molecule is ionized by an intense laser field, the ionization rate depends strongly on the internuclear separation, R. In H2+, the ionization rate exhibits a strong peak structure as a function of R exceeding that of the separated atom limit. Since the ionization potential (IP) decreases for large R, the simple model in which the ionization rate behaves roughly as a monotonic function of the IP according to the ADK theory [1] for direct tunneling ionization breaks down [2]. The enhanced ionization has been explained by the near-degeneracy and the strong dipole coupling between the 1sσg and the 2pσu charge resonance (CR) states, resulting in an efficient nonadiabatic population of the upper dressed CR state from where the electron ionizes through above-barrier ionization (ABI) [2]. However, it was also argued that ABI of the upper CR dressed state is impeded by backscattering of the electron from the hump between the wells [3].
We propose a two-level-system model [4] that accounts for the dressed CR populations and their static-field lifetimes that qualitatively reproduces results for ionization obtained by exact numerical integration of the 3D time-dependent Schrödinger equation and allows to explain the mechanism for the enhanced ionization. We also propose a WKB-based theory that incorporates the two-center nature of the H2+ potential to account for the backscattering of the electron flux due to the outer potential as an alternative to the complex-scaling formulation and MOADK theory [6] for obtaining ionization rates. We discuss the importance of reflection effects from the hump between the wells on the enhanced ionization of H2+ , which are absent in the MOADK theory [6].
[1] M. V. Ammosov, N. B. Delone, and V. P. Krainov, Sov. Phys. JETP 64, 1191 (1986)
[2] T. Zuo and A. D. Bandrauk, Phys. Rev. A 52, R2511 (1995)
[3] Z. Mulyukov, M. Pont, and R. Shakeshaft, Phys. Rev. A 54, 5 (1996)
[4] F. Kelkensberg, G. Sansone, M. Y. Ivanov, and M. Vrakking, Phys. Chem. Chem. Phys. 13, 8647 (2011)
[5] M. Plummer and J. F. McCann, Journal of Physics B: Atomic, Molecular and Optical Physics 29, 4625 (1996)
[6] Tong, X. M. and Zhao, Z. X. and Lin, C. D., Phys. Rev. A 66, 3 (2002)
We propose a two-level-system model [4] that accounts for the dressed CR populations and their static-field lifetimes that qualitatively reproduces results for ionization obtained by exact numerical integration of the 3D time-dependent Schrödinger equation and allows to explain the mechanism for the enhanced ionization. We also propose a WKB-based theory that incorporates the two-center nature of the H2+ potential to account for the backscattering of the electron flux due to the outer potential as an alternative to the complex-scaling formulation and MOADK theory [6] for obtaining ionization rates. We discuss the importance of reflection effects from the hump between the wells on the enhanced ionization of H2+ , which are absent in the MOADK theory [6].
[1] M. V. Ammosov, N. B. Delone, and V. P. Krainov, Sov. Phys. JETP 64, 1191 (1986)
[2] T. Zuo and A. D. Bandrauk, Phys. Rev. A 52, R2511 (1995)
[3] Z. Mulyukov, M. Pont, and R. Shakeshaft, Phys. Rev. A 54, 5 (1996)
[4] F. Kelkensberg, G. Sansone, M. Y. Ivanov, and M. Vrakking, Phys. Chem. Chem. Phys. 13, 8647 (2011)
[5] M. Plummer and J. F. McCann, Journal of Physics B: Atomic, Molecular and Optical Physics 29, 4625 (1996)
[6] Tong, X. M. and Zhao, Z. X. and Lin, C. D., Phys. Rev. A 66, 3 (2002)
*This work was supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES) under Award Number DE-SC0023192
Publication: Charge-Resonance Dynamics and Backscattering Effects in Enhanced Ionization of H2+ in intense, long-wavelength fields, in preparation
Presenters
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R. Esteban Goetz
- University of Connecticut