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Title: Is there a nonzero tunneling delay in strong-field ionization?
Plain: An attoclock uses a rotating laser field, like the hand of a clock, to time when an electron escapes an atom by tunneling. Experiments and analyses disagree on whether the escape takes a finite time or none.
Precise: In elliptically polarized strong-field ionization of atomic hydrogen or helium, extract the tunneling delay $\tau_T$ from the photoelectron momentum offset angle after subtracting the Coulomb deflection computed from the full time-dependent Schrodinger equation, and decide whether $\tau_T = 0$ within resolution. A 2019 hydrogen experiment (Sainadh et al., Nature) reported tau_T below about $1.8e-18\,\mathrm{s}$.
Settled by: Agreement between calibrated attoclock measurements on hydrogen at several intensities and a clock-model prediction.
Kind: well-posed
Answer type: value
References: (empty)
Literature status: contested
Status note: 2025 analyses (e.g. arXiv:2503.07859) continue to compare attoclock and Larmor-clock interpretations of strong-field tunneling.
Posed since: 2008