Development of multi-channel apparatus for electron-atom Compton scattering to study the momentum distribution of atoms in a molecule

Electron-atom Compton profiles due to the intramolecular motions of the H and D atoms in HD

We report an atomic momentum spectroscopy (AMS) experiment on HD, performed at a scattering angle of 135° and at an incident electron energy of 2.0 keV. The electron-atom Compton profiles due to the intramolecular motions of the H and D atoms in HD were obtained. The two Compton profiles are shown to be identical with each other in both shape and intensity, proving that the experimental responses of the intramolecular atomic motions are disentangled from the effect of molecular translational motion. It is also shown that the Compton profiles are in agreement with associated quantum chemistry-based calculations, indicating that the large momentum transfer limit is achieved under the experimental conditions. These observations demonstrate the ability of AMS not only to map the intramolecular motion of each atom with different masses but also to perform elemental composition analysis of a molecular system.

Asymptotic behavior of the electron-atom Compton profile due to the intramolecular H-atom motion in H2

We report the asymptotic behavior of the electron-atom Compton profile due to the intramolecular H-atom motion in H₂. The experiment has been performed at a scattering angle of 135° and at incident electron energies from 1.0 to 2.2 keV, thus covering a momentum transfer (K) range from 15.8 to 23.5 a.u. It is shown that with the increase in K, the Compton profile changes in shape and becomes more symmetric. Furthermore, it is found that the experiment reaches the limit of sufficiently large K at an incident electron energy of 2.0 keV, where the plane-wave impulse approximation is applicable to directly relate the Compton profile to the momentum distribution of the H atom.

Development of an Electron-Atom Compton Scattering Apparatus Using a Picosecond Pulsed Electron Gun

An apparatus has been developed for electron-atom Compton scattering experiments that can employ a pulsed laser and a picosecond pulsed electron beam in a pump-and-probe scheme. The design and technical details of the apparatus are described. Furthermore, experimental results on the Xe atom in its ground state are presented to illustrate the performance of the pulsed electron gun and the detection and spectrometric capabilities for scattered electrons. The scope of future application is also discussed, involving real-time measurement of intramolecular force acting on each constituent atom with different mass numbers, in a transient, evolving system during a molecular reaction.