  We study laser-assisted photodetachment time delays by attosecond pulse
trains from the closed-shell negative ions F- and Cl-. We investigate the
separability of the delay into two contributions: (i) the Wigner-like delay
associated with one-photon ionization by the attosecond pulse train and (ii)
the delay associated with exchange of an additional laser photon in the
presence of the potential of the remaining target. Based on the asymptotic form
of the wave packet, the latter term is expected to be negligible because the
ion is neutralized leading to a vanishing laser-ion interaction with increasing
electron-atom separation. While this asymptotic behavior is verified at high
photoelectron energies, we also quantify sharp deviations at low photoelectron
energies. Further, these low-energy delays are clearly different for the two
studied anions indicating a breakdown of the universality of laser-ion induced
delays. The fact that the short-range potential can induce a delay of as much
as 50 as can have implications for the interpretation of delay measurements
also in other systems that lack long-range potential.
