Driving Rabi oscillations at the giant dipole resonance in xenon

Free-electron lasers (FELs) produce short and very intense light pulses in the XUV and x-ray regimes. We investigate the possibility to drive Rabi oscillations in xenon with an intense FEL pulse by using the unusually large dipole strength of the giant dipole resonance (GDR). The GDR decays within less than 30 as due to its position, which is above the $4d$ ionization threshold. We find that intensities around ${10}^{18}\mathrm{W}/{\mathrm{cm}}^2$ are required to induce Rabi oscillations with a period comparable to the lifetime. The pulse duration should not exceed 100 as because xenon will be fully ionized within a few lifetimes. Rabi oscillations reveal themselves also in the photoelectron spectrum in the form of Autler-Townes splittings extending over several tens of electronvolts.

Figure 1

The population of (a) the ground state, (b) a hole in the $4d$ shell, and (c) a hole in the $5s$ or $5p$ shell in atomic xenon. The instantaneous peak intensity of the 36-as-long (FWHM) Gaussian pulse with a center photon energy of 109 eV is varied from $2.3\times {10}^{17}$ to $1.2\times {10}^{18}\mathrm{W}/{\mathrm{cm}}^2$.

Figure 2

The final $4d$ hole population as a function of pulse intensity for different center photon energies $\omega$ [panels (a)–(c)] and two pulse durations, 36 as (blue solid line) and 73 as (red dashed line).

Figure 3

The final $4d$ hole population as a function of pulse intensity and center pulse photon energy. The pulse duration is (a) 36 as and (b) 73 as.

Figure 4

The photoelectron spectrum as a function of the pulse intensity. The photon energy is centered at 109 eV and the pulse duration is (a) 36 as and (b) 73 as.

Figure 5

The photoelectron spectrum as a function of the pulse intensity. The pulse has a duration of 73 as and the photon energy is centered (a) at 136 eV and (b) at 82 eV.