Molecular above-threshold-ionization spectra: The effect of moving nuclei

Journal Article · Wed Jan 01 04:00:00 EST 2003 · Physical Review. A

DOI:https://doi.org/10.1103/PhysRevA.67.013407· OSTI ID:20634140

Bandrauk, Andre D; Chelkowski, S; Kawata, Isao ^[1]

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1. Universite de Sherbrooke, Quebec J1K 2R1 (Canada)

Exact non-Born-Oppenheimer simulations of a one-dimensional model of one-electron H{sub 2}{sup +} and linear H{sub 3}{sup 2+} in an intense short laser pulse are used to investigate the nonlinear multiphoton electron emission spectra, called above threshold ionization (ATI). Due to the rapid proton motion on near-femtosecond time scale, the ATI spectra are found to be produced at the critical internuclear distance R{sub c}{approx}7-8 a.u., leading to charge-resonance-enhanced ionization (CREI). As a consequence, maxima in the ATI spectra are displaced with respect to the similar H-atom spectra by a laser-induced Stark energy E{sub M}R{sub c}/2, where E{sub M} is the maximum amplitude of the laser field. Highly oscillating ATI spectra occur, which are enhanced by the nuclear motion. These are interpreted as due to coherent excitations of the lowest unoccupied molecular orbitals and highest occupied molecular orbitals, which are also responsible for CREI. Electron rescattering effects in the energy regions of 10U{sub p} and 8U{sub p}, where U{sub p} is the ponderomotive energy, are shown to be substantially reduced due to the rapid molecular dissociation and Coulomb explosion. Nevertheless, the ATI spectra in these energy regions reflect the different electron energies in the rescattering process. Fine structures of the ATI spectra are found to be enhanced by moving nuclei, reflecting the enhancement of resonant transitions by varying Franck-Condon factors during the nuclear motion.

• OSTI ID: 20634140
• Journal Information: Physical Review. A, Journal Name: Physical Review. A Journal Issue: 1 Vol. 67; ISSN 1050-2947; ISSN PLRAAN
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
AMPLITUDES
ATOMS
BORN-OPPENHEIMER APPROXIMATION
COMPUTERIZED SIMULATION
DISSOCIATION
DISTANCE
ELECTRON EMISSION
ELECTRONS
EMISSION SPECTRA
EXCITATION
FINE STRUCTURE
HYDROGEN IONS 2 PLUS
LASER RADIATION
MULTI-PHOTON PROCESSES
NONLINEAR PROBLEMS
NUCLEI
ONE-DIMENSIONAL CALCULATIONS
PHOTOIONIZATION
PONDEROMOTIVE FORCE
PROTONS
PULSES
RESCATTERING
RESONANCE