Strong dependence of photoionization time delay on energy and angle in the neighborhood of Fano resonances

We uncover dramatic variations of the Wigner photoemission time delay with energy and angle in the vicinity of a Fano resonance with the time delay taking opposite signs at different angles at the same energy as well as at the opposite sides of the resonance at the same angle. These variations are illustrated by choosing the Ne $2s\to 3p$ autoionizing state as a case study. Moreover, we demonstrate the existence of strikingly significant changes in time delay due to relativistic effects despite Ne being a low-$Z$ atom. This finding shows the possibility for utilizing time delay chronoscopy as a route towards experimental probing of relativistic interactions and the phases of individual transition matrix elements upon atomic photoionization of low-$Z$ atoms. Finally, we develop a practical parametrization to model and explain the angle and energy variation of the autoionizing resonance time delay in the nonrelativistic limit.

Figure 1

Phases in radians (left panels) and associated time delays in picoseconds (right panels) for the Ne $2p_{1/2}$ amplitudes of Eq. (4) (top panels) and Eq. (5) (bottom panels).

Figure 2

Average time delay, Eq. (7), for the photoemission from the $2p_{1/2}$ subshell of Ne in the vicinity of the $2s\to 3p$ autoionizing resonance.

Figure 3

Averaged time delays for the photoemission from the $2p_{1/2}$ and $2p_{3/2}$ subshells of Ne in the vicinity of the $2s\to 3p$ autoionizing resonance.

Figure 4

Average time delay for photoemission from the unresolved $2p$ subshell of Ne in the vicinity of the $2s\to 3p$ autoionizing resonance. Top panel: RRPA + RMQDT calculation. Bottom panel: Analytical model, Eq. (8).

Figure 5

Moduli (left panel) and phases (right panel) of the resonant amplitudes $T_a$ and $T_b$, Eq. (8).