Method and apparatus for measuring the time of short events, such as characteristics of a source of short radiation pulses or lifetime of excited states of a sample. The method and apparatus is based on a multi-step photoemission process from an active element target exhibiting superlinear photoemission. A short prompt radiation pulse is used to raise electrons to an excited state, and a following overlapping short probe pulse is used to raise the excited electrons to the vacuum level where they leave the sample, changing its charge state. The number of escaped electrons is measured as a function of the time delay between the prompt and probe pulses to provide the sought after information. Preferably, the charged target is suspended or supported in an electric field, and the voltage needed to restore the charge-changed target to its original position is used.