Opportunities in the VUV and Soft X-ray Regions. Neville V. Smith, Lawrence Berkeley National Laboratory, Berkeley, California 94720 USA

The Advanced Light Source is a 1.5-1.9 GeV storage ring designed for very high brightness in the VUV and soft x-ray region. This talk will summarize accomplishments so far and examine opportunities for the future.

An early, and perhaps not widely anticipated, success was in the area of soft x-ray emission spectroscopy (XES) where the small size of the illuminated spot is compatible with narrow entrance slits of the spectrometer and permits acceptable resolution. Likewise, gas phase absorption spectroscopy has been revolutionized with unprecedented resolving power of 64000. It is in the area of spatially resolved techniques (spectromicroscopies), however, that much of the promise lies. Spatial resolution may be achieved by using photon optics (zone plates, Schwartzchild mirrors or Kirkpatrick-Baez pairs) as in the scanning transmission x-ray microscope (STXM) and scanning photoemission microscope (SPEM), or by using electron optics as in the imaging technique of photoelectron emission microscopy (PEEM). These various methods are being pursued vigorously at the ALS and elsewhere, and examples of recent work will be presented in the areas of polymer chemistry, silicon wafer analysis and cell biology. The advantage of spectromicroscopy is that it is possible to go beyond mere elemental analysis and to obtain chemical binding information.

Growing areas include soft x-ray magnetic circular dichroism (MCD) and molecular environmental science. MCD spectroscopy is powerful in its own right for the study of magnetic materials, surfaces and films. It also provides a contrast mechanism for magnetic spectromicroscopy. Another growing area is the use of soft x-ray absorption spectroscopy (XAS) in molecular environmental science where a principal question is the "speciation" of metal contaminants. The STXM technique is likely to be of importance in the study of the role of microbes in mediating chemical processes of environmental concern.