IR-assisted ionization of He by attosecond XUV radiation

In this work we characterize the underlying processes behind the IR-assisted ionization of helium by extreme ultra violet (XUV) attosecond radiation. We show that, if used in the form of an attosecond pulse train, the XUV radiation can have a good spectral resolution as well as good temporal resolution. Our experimental data and associated theoretical calculations show how to use the properties of attosecond XUV radiation to induce a desired excited state of helium, and how to tune the IR laser electric field to control the ionization pathways.