X-ray-photon Compton scattering by a linear molecule

Abstract

We formulate a nonrelativistic quantum theory for the nonresonant inelastic scattering process of an x-ray photon by a free linear molecule outside of the impulse approximation framework. We find a strong orientation effect dependent on changes in the schemes of the proposed experiments. Calculations of the absolute values and forms for the double differential scattering cross sections are carried out for the HF molecule and have a predictive character. The presented theory is of a general nature, and its applicability to a particular linear molecule is constrained only by the demand of correctness of nonrelativistic methods for constructing molecular scattering orbitals.

Kinematically complete experimental study of Compton scattering at helium atoms near the threshold

“…For slightly higher momentum transfers , that is, photon energies of ∼6 keV, one can expect the signi cance of correlations in the scattering states to diminish, simplifying the theoretical description. As has been pointed out recently, measuring the momentum transfer to the nucleus in this case will give access to the Dyson orbitals [11].…”

“…To a large extent, this lack of detailed experiments left further progress in the eld of Compton scattering to theory. Due to missing experimental techniques, much of the potential of using Compton scattering as a tool in molecular physics remained untapped [11]. The small cross-section of 10 −24 cm 2 (six orders of magnitude below typical photoabsorption cross-sections at the respective thresholds), together with the small collection solid angle of typical photon detectors, has so far prohibited coincidence experiments on free atoms and molecules.…”

Method of Accounting for Higher Harmonics in the Calculation of the Electronic Structure of the States of a Linear Molecule Excited by High-Intensity X-Rays

“…Studies of the process of ionization / excitation of molecular systems [9][10][11] carried out so far show that the creation of a vacancy in the molecular core can lead to a significant redistribution of the electron charge and has a many-electron character, which has certain peculiarities when the system is ionized by high-intensity X-rays [12][13][14]. When a molecule absorbs x-ray photons, innershell multiple ionization induces fragmentation dynamics [15].…”

“…In the OC approach, the mathematical apparatus developed for atomic calculations is easily generalized to the case of molecular calculations for one-and two-particle matrix elements which form the basis for most of the calculated physical characteristics of polyatomic systems [24,25]. In the course of its development, the OC method was implemented through solving a secular equation using basic Hartree-Fock functions obtained in the field of the central atom of the molecular system [13,14,26], and through solving a system of coupled integro-differential equations [27,28]. The principal disadvantage of the OC representation of MO is the slow convergence of the expansions in spherical harmonics.…”