Abstract

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 1cm path length, therefore, the fraction of photons absorbed is only about 10⁻⁷. These absorbed photons produce ions, electrons, and fluorescence from excited states. Whether we use photoelectron spectroscopy to study electrons or monochromators to disperse the fluorescence radiation, we sample only a small fraction of that produced. Signals are, therefore, extremely small. Because of the lack of intense light sources in the VUV, many interesting experiments cannot be performed. As a practical example of what can be achieved by a high flux source, we present here some results using undispersed synchrotron radiation from Tantalus, the low-energy (240 MeV) storage ring at Stoughton, Wisconsin.

© 1988 Optical Society of America