Distortion of the Ionization Cross Section of He by the Coherence Properties of a C6+ Beam

Francisco Navarrete,Marcelo Ciappina,Raúl Barrachina

doi:10.3390/atoms7010031

Francisco Navarrete, Marcelo Ciappina + Show 1 more

Open Access

https://doi.org/10.3390/atoms7010031

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Abstract

We analyze the influence of the coherence of the projectile’s beam in scattering phenomena. We focus our study in the ionization of He by C 6 + projectiles at 100 MeV/amu. We assess the influence of this effect by performing a Born initial state and continuum distorted wave final state (CDW-B1) calculation together with a rigorous procedure to account for the initial coherence properties of the projectile’s beam. These calculations, which had been previously performed for only the scattering and perpendicular collision planes and within the First Born approximation (FBA), were repeated for an ampler set of collision planes. Additionally, a more refined method to describe the applicability of the aforementioned procedure, is used. We achieve a better qualitative agreement with the experimental results.

Highlights

In general, there is a surprising agreement of the predictions made even for the most basic first order theoretical models like, for instance, the first Born approximation (FBA), which ignores the interaction between the nuclei in the collision
We used a CDW-B1 approximation, refining a previous First Born approximation (FBA) [20], which has been successfully applied to convolutions similar to the one we perform [22,25,26]
Stripped carbon ions at 100 MeV are used as projectiles and neutral He atom as target, which we model as a hydrogen-like atom with an effective charge given by the first ionization energy

Summary

Introduction

The awareness of the relevance of the projectile’s beam coherence effects in ion-atom and ion-molecule collisions has motivated an extensive study on this subject in the recent years [1,2,3,4,5,6,7,8,9,10,11,12,13,14]. When an initially spatially constrained wave packet scatters through a structured target, the outcome of this process should depend strongly on the distance between the target region and the projectile source This can be understood by noting that if their separation is small, the wave packet could not "illuminate" the whole target in a coherent way, but only a fraction of it. In general, there is a surprising agreement of the predictions made even for the most basic first order theoretical models like, for instance, the first Born approximation (FBA), which ignores the interaction between the nuclei in the collision This agreement should improve as we decrease the Sommerfeld parameter ZP /v, being ZP the charge and v the initial velocity of the projectile. A Sommerfeld parameter of ≈ 0.1 should make it ideal to be described by almost any calculation method while, as we mentioned, they fail to give even a qualitative description of the FDCS at certain collision planes

An Incoherent Mixture of Quantum States

Mathematical Description

Calculation of the Incoherent FDCS

Results

Conclusions