Fourier Transform of Spherically Averaged Momentum Densities

Abstract

The first (e,2e) experiments had as their objective the demonstration of the feasibility of the technique¹. Energy resolution was several eV and the signal rate was low, however, the early measurements clearly showed that the electron knock-out coincidence technique could be used for obtaining single electron momentum densities. Once the feasibility of the technique was established new instruments were constructed with better energy resolution and greater efficiency.^2,3,4,5 For structure measurements the noncoplanar symmetric geometry was preferred because of the ease with which the data could be converted to momentum densities within the context of the plane wave impulse approximation. During this phase a great deal of data was accumulated on atoms and small molecules. The emphasis was on the assignment of electronic states, the investigation of satellite structure and the comparison between momentum densities calculated from atomic and molecular wave-functions and the corresponding experimental measurements.⁶ In this second phase there was a dramatic increase in the quality of the experimental data, however, the data were not of sufficient precision to make more than qualitative comparisons with theory. An important criticism of the technique was that all the experimental data looked qualitatively similar and most analyses were essentially descriptive.

Research supported by NSF grant CHE 8205884 and the Computer Science Center of the University of Maryland USA