High-precision intensity-selective observation of multiphoton ionization: a new method of photoelectron spectroscopy.

We have developed a novel method of time-of-f light (TOF) photoelectron spectroscopy that permits observation of multiphoton ionizations with extremely high precision, especially for low-probability events. By scanning the laser-produced ionization region across a pinhole we can select specific laser peak intensities. The volumes occupied by low intensities rise rapidly compared with traditional straight TOF spectroscopy, resulting in high signal gains. This technique presents a new way of observing fundamental laser-matter interactions.