J. Mirandaª, O.G. de Luciob and M.F. Lugo-Liconac
ª Instituto de Física, Universidad Nacional Autónoma de México, Apartado Postal 20-364, 01000 México, D.F., MÉXICO.
b Department of Physics, University of Missouri-Rolla, 1870 Miner Circle, Rolla, MO 65409-0640, USA.
c Facultad de Química, Universidad Nacional Autónoma de México, Ciudad Universitaria, 04510 México, D.F., MÉXICO.
Recibido el 2 de marzo de 2006
Aceptado el 18 de agosto de 2006
Abstract
The emission of X-rays after the excitation with photons, electrons, or light ions (such as protons or deuterons), has been extensively studied. However, when heavier ions are used as primary radiation to induce this effect, other phenomena appear that are not present in the other cases. They include, for example, the formation of short-lived molecules, the capture of electrons from the target atom by the incoming ion, and a strong increase in the multiple ionization of the target atom. Usually, the ionization cross sections are higher as compared to those of photons, electrons, or protons. Furthermore, when thick targets are irradiated with heavy ions, there is a larger probability to create defects in the material, and also a higher stopping power in the target material. All these differences make the study of the X-ray production by heavy ions a problem not fully understood, and far from being applied in an extensive manner to the characterization of materials. In this work, an explanation of the basic phenomena is presented, together with possible uses of the emission of X-rays by the impact of the heavy ions, as an extension of the traditional method Particle Induced X-ray Emission (PIXE).
Keywords: X-rays; ionization; heavy ion impact; PIXE.
Resumen
La emisión de rayos X debida a la excitación por fotones, electrones o iones ligeros (como protones o deuterones), se ha estudiado ampliamente. Sin embargo, cuando se usan iones más pesados como radiación primaria para inducir este efecto, aparecen otros fenómenos que no están presentes en los otros casos. Incluyen, por ejemplo, la formación de moléculas de vida corta, la captura de electrones del átomo blanco por parte del ion incidente, y un fuerte aumento en la ionización múltiple del átomo blanco. Usualmente, las secciones de ionización son mayores que en el caso de fotones, electrones o protones. Más aún, cuando se irradian blancos gruesos con iones pesados, hay una mayor probabilidad de crear defectos en el material, habiendo también un mayor poder de frenado en el material blanco. Todas estas diferencias hacen que el estudio de la producción de rayos X por el impacto de iones pesados sea un problema no entendido del todo. En este trabajo, se hace una explicación de los fenómenos básicos, junto con los posibles usos de la emisión de los rayos X por el impacto de iones pesados, como una extensión del método tradicional de Emisión de rayos X inducida por partículas (PIXE).
Descriptores: Rayos X; ionización; iones pesados; PIXE.
PACS: 32.80.Hd; 33.50.Hv; 34.50.Dy
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Acknowledgements
This work was partially supported by CONACYT (contract 40122-F).
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