Pump-control-Probe experiments would allow, for the first time, a use of three ultrashort pulses: attosecond VUV pulse trains to coherently initiate a simple chemical reaction, IR pulse to control and steer it, and soft X-ray pulse in the water window to probe it.

In the above theoretical paper, the calculated TA spectra around carbon k-edge show how the ultrafast nuclear dynamics of a twisted/pyramidized ethylene molecule, excited by the 5th harmonic, changes by means of different charge localization pathways. Here, we are proposing to realize these experiments with the addition of a laser pulse that would control the conical intersection dynamics.

Unraveling, and controlling such ultrafast processes on a atto- and few-fs time scale is essential for understanding photochemical reactions and light-harvesting processes, that are not yet well understood due to the lack of the proposed experimental tools.