Video LEED

Figure 2 Schematic diagram of a video LEED system used to generate intensity versus voltage curves of electrons diffracted from ordered surfaces. The I -V curves are compared to theory in solving a surface structure...

LEED, video-LEED, low energy electron diffraction (Christmann et al.,... 

To date, the usual way of recording the LEED pattern is a light-sensitive video camera with a suitable image-processing system. In older systems movable Earaday cups (EC) were used which detected the electron current directly. Because of long data acquisition times and the problems of transferring motion into UHV, these systems are mostly out of use nowadays. 

Over the last decade both the speed and accuracy of data acquisition and the sensitivity of the LEED experiment have been significantly improved. In most structure determination experiments the LEED patterns are displayed on a phosphor screen. LEED I-V curves are then measured by photometric or photographic means. Fast data acquisition systems have been developed that record LEED patterns with video cameras interfaced to computers and generate I-V curves during the experiment./3,4/ The sensitivity of LEED is also being greatly increased with the development of instruments that can detect single... 

In addition, we thank Mohammad El-Khateeb of Jordan University of Science and Technology, who joined one meeting via video conference and Alastair Hay of the University of Leeds, United Kingdom, and Richard W. Niemeier of the U.S. National Institute for Occupational Safety and Health, Cincinnati, Ohio, who had shorter journeys but provided no less valuable insights to the committee. 

The teaching sequences, and associated diagnostic questions, can be found at http //www.education.leeds.ac.uk/research/scienceed/epse teach resources.htm Analysis of the video records of the lessons indicates that the conceptual content of both the physics and biology teaching sequences was followed quite closely by... 

---