科研之友
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摘要
A hydrogen atom, initially prepared in the 2s and/or 2p(m = +/- 1) states, is assumed irradiated by 0.8 keV (1.5 nm) photons in pulses of 1-250 fs duration and intensities in the range 10(20) to 10(23) W/cm(2). Solving the corresponding time-dependent Schrodinger equation from first principles, we show that the ionization and excitation dynamics of the laser-atom system is strongly influenced by interactions beyond the electric dipole approximation. A beyond-dipole two-photon Raman-like transition between the 2s and 2p(m = +/- 1) states is found to completely dominate the underlying laser-matter interaction. It turns out that the large difference in the ionization rates of the 2s and 2p(m = +/- 1) states is important in this context, effectively leading to a symmetry breaking in the corresponding (beyond-dipole) bound-bound dynamics with the result that a net population transfer between the states occurs throughout the laser-matter interaction period. Varying the x-ray exposure time as well as the laser intensity, we probe the phenomenon as the bound wave packet oscillates between having 2s and 2p(m = +/- 1) character, eventually giving rise to a Rabi-like oscillation pattern in the populations.
- 出版日期2016-6-27
