X-Ray Compton-Raman Scattering from Atomic Inner-Shell Electrons

Abstract

Inelastic scattering of 241 Am 59.57-keVy rays from Cu and Fe was measured in coincidence with the ^-fluorescence x rays. The spectrum due to the scattering by the #-shell electrons shows the coexistence of a Compton-type and a Raman-type scattering. Doublephoton Thomson-type scattering is also identified, which is weaker than the usual Compton scattering by a factor of about 4 x 10~3.PACS numbers: 78.70.Ck X-ray inelastic scattering by a free electron is completely characterized by the energy and the momentum conservation laws. This phenomenon is the well-known Compton scattering. In contrast to Compton scattering, the feature of x-ray inelastic scattering by a bound electron varies with the value of ka even when Ho) X » E b , 1,2 where Hk is the momentum transfer and a is the radius of the binding orbital, while #a>i and E b are the energies of the incident photon and the binding orbital, respectively.When ka » 1, the peak position of the spectrum is determined only by the primary energy and by the scattering angle, but it is independent of the type of scattering atom. This is a distinct feature of Compton scattering, although Doppler broadening of the normal Compton line takes place: The spectrum includes information on the momentum distribution of the electrons in the initial state. This phenomenon is Compton scattering by a bound electron. On the contrary, when ka < 1, the peak position of the spectrum corresponds to the absorption edge of the relevant atomic orbital, but it depends neither on the scattering angle nor on the primary photon energy. The spectrum, in this case, is related to the dipole moment strength per energy. This phenomenon is x-ray Raman scattering. When ka > 1, so-called Compton-Raman scattering takes place. In this case, transition phenomena between the above two typical cases, Compton and Raman type, are expected to appear. The nature of the phenomena is not yet well understood, partly because there has been no reliable low-energy experiment so far which investigated separately the spectrum due to electrons in a single shell.In the present experiment, inelastic scattering spectra from AT-shell electrons have been measured on Cu {ka =1.02) and Fe {ka =1.16) by means of coincidence counting between the low-energy y rays scattered and the AT-fluorescence x rays subsequently emitted. 3 "" 9 By this technique, certain basic properties have been revealed for the x-ray inelastic scattering in the region where ka > 1.The experimental apparatus, arranged as shown in Fig.

Inelastic x-ray scattering from copperK-shell electrons at intermediate momentum transfers

“…In summary, our observations support the basic theoretical result that in the range of momentum transfer intermediate between that for photoabsorption (qa ^C1) and that for inelastic scattering in the impulse-approximation limit, the scattering length is not split into two features of approximately equal strength as reported in Ref. 5, but rather most of the scattering involves an energy transfer only ;S 5 keV above the binding energy. This conclusion confirms some of the comments by Manninen 7 and contradicts a recent calculation by Ohmura and Sato 17 based on a more approximate oneelectron model than the one presented here.…”

“…8 A source of these false events is detector-todetector scattering 5,7 (which gave a significant spectral feature in Ref. 5). In these events a single x ray scatters from the fluorescence detector into the scattered x-ray detector.…”

Inelastic X-Ray Scattering From Copper K Shell Electrons at Intermediate Momentum Transfer

“…A similar experiment has been performed for 59.6 keV x rays scattered from the K shell electrons of Fe and Cu. [2] However, the spectra in that work were distorted by false coincidences possibly caused by detector to detector scattering.…”

Recent Advances in Compton Scattering

“…From the quantitative point of view both changes are dependent on the approximation used. In fact, Namikawa and Hosoya [25] claimed to observe a shift of the Compton profile as well as a Raman-type peak close to the K-edge of iron and copper. Their findings, however, were put in doubt by Manninen [26], who suspected that this result could be due to false coincidences overlooked in [25].…”

“…In fact, Namikawa and Hosoya [25] claimed to observe a shift of the Compton profile as well as a Raman-type peak close to the K-edge of iron and copper. Their findings, however, were put in doubt by Manninen [26], who suspected that this result could be due to false coincidences overlooked in [25]. Much earlier, in 1979, Pattison and Schneider [27] have found that the impulse approximation works well for Au and Pb.…”