A finite-pulse virtual-sequential model for the two-photon double ionization of Ne and Ar.*

The pump-probe experiments enabled by XFELs [1,2] will allow us to directly observe correlated electronic motion with attosecond time resolution by detecting photoelectron pairs in coincidence. In helium, the transition between the non-sequential and sequential regime in two-photon double ionization (TPDI) is well explained by a virtual-sequential model (VS) [3]. Much less is known, however, about TPDI in more complex atoms. Recently, we have extended the VS model to arbitrary light pulses [4], using multi-channel scattering states for the single ionization of both the neutral and the ionized target [5]. This finite-pulse virtual-sequential model (FPVSM) reproduces all the qualitative features of ab-initio angularly integrated observables [6,7]. As a step towards the description of TPDI in polyelectronic atoms, we used the FPVSM to calculate the joint photoelectron energy distribution and sharing in neon and argon. Our simulations reveal two-particle interferences and the signature of autoionizing states, which should be observable with current experimental technologies [2].

[1] J. Duris et al., Nat. Photonics 14, 30 (2020).

[2] I. Orfanos et al., PRA 106, 043117 (2022).

[3] D Horner et al., PRA 76 030701 (R) (2007).

[4] S. Chattopadhyay et al., (In Preparation).

[5] T Carette et al., PRA 87 023420 (2013).

[6] J Feist et al., PRL 103 063002 (2009).

[7] A Palacios et al., PRL 103 253001 (2009).