The Compton profile of neon: Experimental study beyond the impulse approximation

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Abstract
High‐precision relative energy‐loss spectra of 25 keV electrons scattered from neon atoms are measured in the momentum transfer range 0.5 a.u.<K< 15 a.u. The corresponding generalized oscillator strengths are made absolute by use of the Bethe sum rule and then converted to Compton profiles (CP). These CP’s are shown to be K‐independent in the K ranges 5–7 and 13–15 a.u., where effective valence and total CP’s are respectively defined. Neither of these profiles is reproduced by the impulse approximation (IA) because of the existence of the so‐called Compton defect, i.e., a lack of symmetry in the intensity of the observed profile on the positive and negative q sides (q is the usual Compton parameter), and a shift of its maximum from the q=0 position predicted by the IA. Following a theoretical treatment proposed by Tavard and co‐workers for H and He, the experimental profiles are divided into their symmetrical (SCP) and antisymmetrical (ASCP) parts with respect to the q variable: the ASCP agrees with Tavard’s qualitative predictions, while the SCP is not reproduced by the IA. The remaining difference might be attributed to higher order terms in Tavard’s series development of the Born operator. Comparison of our results to previous experimental ones is also given.