The interaction of excited atoms and few-cycle laser pulses

This work describes the first observations of the ionisation of neon in a metastable atomic state utilising a strong-field, few-cycle light pulse. We compare the observations to theoretical predictions based on the Ammosov-Delone-Krainov (ADK) theory and a solution to the time-dependent Schrödinger equation (TDSE). The TDSE provides better agreement with the experimental data than the ADK theory. We optically pump the target atomic species and measure the ionisation rate as the a function of different steady-state populations in the fine structure of the target state which shows significant ionisation rate dependence on populations of spin-polarised states. The physical mechanism for this effect is unknown.The work of K.B. was supported by the United States National Science Foundation under grant PHY-1430245. We acknowledge support of the Australian Research Council in the form of the Discovery Project DP120101805 and DP110101894, and of the ARC Centre of Excellence for Coherent X-ray Science. HX was supported by an ARC Discovery Early Career Researcher Award (DE 130101628). JEC was supported by an Australian Postgraduate Research Award