Two-color stabilization of atomic hydrogen in circularly polarized laser fields

Abstract

Dynamic stabilization of atomic hydrogen against ionization in high-frequency single-and twocolor, circularly polarized laser pulses is observed by numerically solving the three-dimensional, time-dependent Schrödinger equation. The single-color case is revisited and numerically determined ionization rates are compared with both, exact and approximate high-frequency Floquet rates. The position of the peaks in the photoelectron spectra can be explained with the help of dressed initial states. In two-color laser fields of opposite circular polarization the stabilized probability density may be shaped in various ways. For laser frequencies ω1 and ω2 = nω1, n = 2, 3, . . . and sufficiently large excursion amplitudes n + 1 distinct probability density peaks are observed. This may be viewed as the generalization of the well-known "dichotomy" in linearly polarized laser fields, i.e, as "trichotomy," "quatrochotomy," "pentachotomy" etc. All those observed structures and their "hula-hoop"-like dynamics can be understood with the help of high-frequency Floquet theory and the two-color Kramers-Henneberger transformation. The shaping of the probability density in the stabilization regime can be realized without additional loss in the survival probability, as compared to the corresponding single-color results.

Dynamics of H(2p) ionization in ultrashort strong laser pulses

“…We now return to the question of which frame is the most efficient for short laser pulses. In figure 1, we show the highest populated l-value for calculations in the length gauge and the KH frame, respectively, for a 5-cycle pulse, cf equation (13), with increasing intensity (upper figure) and an N cycle pulse with fixed intensity (lower figure). By highest populated l is meant the l value in equation (16) which is such that the probability for populating any higher state is always smaller than 10 −3 during the pulse.…”

Photoelectron spectra with Qprop and t-SURFF

“…The remaining steps, i.e., performing the time integrals (26), (27) or (33), (34) (smoothed by the Hanning window ( 16)) and calculating the partial spectra (21) or (30) Angle-resolved spectra whose range and resolution are defined in the parameter file tsurff.param are written to text files named tsurff-polari p .dat. Here, i p is the number of the process which produced the result.…”

“…TDSE simulations for a similar setup where reported in, e.g., [31,32,33]. Qprop in propagation mode 44 was used in [34,29,32].…”

Attosecond-magnetic-field-pulse generation by coherent circular molecular electron wave packets

“…(0.053 nm), i.e., atom ic-m olecular subnanom eter dim ensions, thus generating strong m agnetic fields B ~ co as discussed above. H igh-frequency strong-field electron dynam ics differs from low -frequency dynam ics and is more sim ply treated in a space translation or acceleration representation o f laser-m atter interaction, in w hich K ram ers-H enneberger (KH) tim e-averaged potentials lead to strong deform ations o f atom ic [25,30] Figs. 1 and 3).…”

“…Electrons at such high frequencies become localized at their maximum excursions a j = E/co2, resulting in positive shifts of their bound-state energies [25,30,31], Thus one expects high-frequency MATI peaks to move to high energies, in con trast to the high-intensity low-frequency case where ac-Stark shifts are negative [30,32,33], The MATI spectra illustrated in Fig. 3 show that each MATI peak is a doublet, with one peak lower and the other higher in energy around the central energies Een = net) -Ip.…”