1. Laboratory for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institute, Villigen 5232, Switzerland
2. Institute of Combustion Technology, German Aerospace Center (DLR), Pfaffenwaldring 38-40, D-70569 Stuttgart, Germany
3. Mass Spectrometry in Reactive Flows, Institute for Combustion and Gas Dynamics (IVG), University Duisburg-Essen, Duisburg 47057, Germany