The interaction of excited atoms and few-cycle laser pulses*

We present the observations of the ionisation of neon in a metastable atomic state utilising a strong-field few\-cycle laser pulse [1,2]. We compare the observations to theoretical predictions based on the Ammosov-Delone-Krainov (ADK) theory [3] and a solution to the time-dependent Schr\"{o}dinger equation (TDSE) [4]. The TDSE provides better agreement with the experimental data than the ADK theory. We optically pump the target atomic species and demonstrate that the ionisation rate depends on the spin state of the target atoms and provide physically transparent interpretation of such a spin dependence in the frameworks of the spin-polarised Hartree-Fock and random-phase approximations [5]. [1] J. E. Calvert {\em et al.}, arXiv:1601.03786, 2016, Sci. Rep. submitted [2] I. A. Ivanov, Sci. Rep. 19002 (2016) [3] M. V. Ammosov {\em et al.}, Sov. Phys. JETP {\b 64}, 425 (1986). [4] X. M. Tong {\em et al.}, Phys. Rev. A {\b 74}, 031405(R) (2006). [5] M. Y. Amus'ya {\em et al.}, Sov. Phys. . JETP {\b 58}, 67 (1983).