Applications of a free electron laser to atomic and molecular physics

With crossed beam experiments in atomic and molecular physics, the gas pressure in the sample chamber is typically of the order of 5 x 10-5 Torr. Furthermore, many of the more interesting investigations such as photoelectron and fluorescence spectroscopy of specific processes have photoionization cross sections in the vicinity of 0.1 Mb (10-19 cm2), or less. In a lcm path length, therefore, the fraction of photons absorbed is only about 10-7. These absorbed photons produce ions, electrons, and fluorescence from excited states. As a practical example of what can be achieved by a high flux source, the authors present some results using undispersed synchrotron radiation from Tantalus, the low-energy (240 MeV) storage ring at Stoughton, Wisconsin