2pi gas phase multichannel electron momentum spectrometer for rapid orbital imaging and multiple ionization studies

The development of two new experimental methods in gas phase photoionization studies is reviewed. These are angle-resolved electron-electron coincidence spectroscopy and angleresolved electron-fragment ion coincidence spectroscopy. The review concentrates on systems which employ time-of-flight techniques for both the electron and ion detections. In addition to a technical description of such a system for both methods, showcase examples of their application in synchrotron radiation-based atomic and molecular physics are presented and discussed.