
Rafael Garcia-MolinaUniversity of Murcia | UM · Department of Physics
Rafael Garcia-Molina
PhD Physics
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197
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Introduction
Skills and Expertise
Additional affiliations
August 2008 - October 2020
April 1991 - July 2008
November 1988 - March 1991
Publications
Publications (197)
The electronic excitation spectrum of a material characterises the response to external electromagnetic perturbations through its energy loss function (ELF), which is obtained from several experimental sources that usually do not completely agree among them. In this work we assess the available ELF of three metals, namely chromium, palladium and sa...
We have determined the depth-dose curve, penetration range, and water equivalent ratio for proton beams of clinical energies in cortical bone by means of a detailed and accurate simulation that combines molecular dynamics and Monte Carlo techniques. The fundamental input quantities (stopping power and energy loss straggling) for the simulation were...
One way of encouraging people's interest in physics is to provide them with rewarding experiences that stimulate their curiosity and at the same time encourage them to seek an explanation for the phenomena they observe. These experiences need to be related to the everyday environment to show that basic but far-reaching physical knowledge is accessi...
Today's society enjoys a welfare state that is largely a consequence of the scientific and technological advances of previous eras (especially the last century). Currently, (non-specialist) citizens interested in scientific topics have access to them in a variety of ways, from the classic formats of books and popular science magazines, television,...
El experimento del ascenso del agua por el interior de un vaso que cubre una vela encendida, sobre un plato con agua, es un recurso didáctico muy utilizado para mostrar a los estudiantes lo que sucede cuando la presión dentro de un recipiente se hace inferior a la presión atmosférica. Aunque el experimento es sencillo, rápido y fácilmente reproduci...
Understanding and quantifying the electronic inelastic interactions of swift ions and electrons in metals is fundamental for many applications of charged particle beams. A common theoretical approach is moreover desirable for the case of both types of projectiles, as large numbers of secondary electrons arise as the result of ion interaction with m...
Resumen
El ascenso de agua dentro de un recipiente invertido que contiene una vela encendida es un típico experimento recreativo cuyo resultado es bien conocido. El nivel del agua sube debido a una reducción de la presión dentro del recipiente, pero la contribución de diferentes procesos (físicos y químicos) a esta explicación todavía es objeto de...
The nanometric track-structure of energetic ion beams in biological media determines the direct physical damage to living cells, which is one of the main responsibles of their killing or inactivation during radiotherapy treatments or under cosmic radiation bombardment. In the present work, detailed track-structure Monte Carlo simulations, performed...
Understanding and predicting the energy loss of swift ions in metals is important for many applications of charged particle beams, such as analysis and modification of materials, and recently for modelling metal nanoparticle radiosensitisation in ion beam cancer therapy. We have calculated the stopping power of the transition metals Pt and Au for p...
Energetic carbon ions are promising projectiles used for cancer radiotherapy. A thorough knowledge of how the energy of these ions is deposited in biological media (mainly composed of liquid water) is required. This can be attained by means of detailed computer simulations, both macroscopically (relevant for appropriately delivering the dose) and a...
The nanometric track-structure of energetic ion beams in biological media determines the direct physical damage to living cells, which is one of the main responsibles of their killing or inactivation during radiotherapy treatments or under cosmic radiation bombardment. In the present work, detailed track-structure Monte Carlo simulations, performed...
Understanding and predicting the energy loss of swift ions in metals is important for many applications of charged particle beams, such as analysis and modification of materials, and recently for modelling metal nanoparticle radiosensitisation in ion beam cancer therapy. We have calculated the stopping power of the transition metals Pt and Au for p...
Nanomaterials made of cerium oxides CeO2 and Ce2O3 have a broad range of applications, from catalysts in automotive, industrial or energy operations to promising materials to enhance hadrontherapy effectiveness in oncological treatments. To elucidate the physico-chemical mechanisms involved in these processes, it is of paramount importance to know...
Nanomaterials made of the cerium oxides CeO$_2$ and Ce$_2$O$_3$ have a broad range of applications, from catalysts in automotive, industrial or energy operations to promising materials to enhance hadrontherapy effectiveness in oncological treatments. To elucidate the physico-chemical mechanisms involved in these processes, it is of paramount import...
Showcasing research by Dr Pablo de Vera, ECT*/FBK (Trento, Italy), and Prof. Isabel Abril and Prof. Rafael Garcia-Molina, Universities of Alacant and Murcia (Spain), respectively.
Excitation and ionisation cross-sections in condensed-phase biomaterials by electrons down to very low energy: application to liquid water and genetic building blocks
A...
Electronic excitations and ionisations produced by electron impact are key processes in the radiation-induced damage mechanisms in materials of biological relevance, underlying important medical and technological applications, including radiotherapy, radiation protection in manned space missions and nanodevice fabrication techniques. However, exper...
The effective use of swift ion beams in cancer treatment (known as hadrontherapy), as well as appropriate protection in manned space missions, rely on the accurate understanding of the energy delivery to cells that damages their genetic information. The key ingredient characterizing the response of a medium to the perturbation induced by charged pa...
Focused electron beam induced deposition (FEBID) is a powerful technique for 3D-printing of complex nanodevices. However, for resolutions below 10 nm, it struggles to control size, morphology and composition of the structures, due to a lack of molecular-level understanding of the underlying irradiation-driven chemistry (IDC). Computational modeling...
The effective use of swift ion beams in cancer treatment (known as hadrontherapy) as well as an appropriate protection in manned space missions rely on the accurate understanding of energy delivery to cells damaging their genetic information. The key ingredient characterizing the response of a medium to the perturbation induced by charged particles...
Electronic excitations and ionisations produced by electron impact are key processes in the radiation-induced damage mechanisms in materials of biological relevance, underlying important medical and technological applications, including radiotherapy, radiation protection in manned space missions and nanodevice fabrication techniques. However, exper...
Focused electron beam induced deposition (FEBID) is a powerful technique for 3D-printing of complex nanodevices. However, for resolutions below 10 nm, it struggles to control size, morphology and composition of the structures, due to a lack of molecular-level understanding of the underlying irradiation-driven chemistry (IDC). Computational modellin...
La recomposición de un rayo de luz blanca, descompuesto inicialmente por un prisma, mediante el uso de otro prisma idéntico e invertido respecto al anterior es imposible y, sin embargo, numerosas fuentes (bibliográficas y de internet) suelen presentar este supuesto experimento como una actividad de fácil ejecución e incuestionable resultado. En est...
The chapters in this book are aimed to show different manifestations of science in the South of the Valencian Country, from Middle Ages to present days
This article (published in a news paper) explains the operation and didactic use of some toys
Carbon nanotube properties can be modified by ion irradiation; therefore it is important to know the manner in which ions deposit energy (how much and where) in the nanotubes. In this work, we have studied, experimentally and with a simulation code, the irradiation of multi-walled carbon nanotubes (MWCNT), supported on a holey amorphous carbon (a-C...
We have performed detailed simulations of the energy spectra, recorded at several angles, of proton and helium ion beams after traversing thin cylindrical targets of different nature (liquid water and ethanol jets, as well as a solid aluminium wire), in order to reproduce a series of measurements intended to assess the stopping power of 0.3–2 MeV i...
A new method is reported for a simple, yet reliable, calculation of electron inelastic mean free paths in insulating and conducting materials, from the very low energies of hot electrons up to the high energies characteristic of electron beams. Through a detailed consideration of the condensed phase nature of the target, as well as the energy trans...
A method is reported for a simple, yet reliable, calculation of electron inelastic mean free paths in condensed phase insulating and conducting materials, from the very low energies of hot electrons up to the high energies characteristic of electron beams. Through a detailed consideration of the energy transferred by the projectile in individual an...
The number and energy of secondary electrons generated around the trajectories of swift protons interacting with biological materials are highly relevant in proton therapy, due to the prominent role of low-energy electrons in the production of biodamage. For a given material, electron energy distributions are determined by the proton energy; and it...
Results of a study of electronic energy loss of low keV protons interacting with multilayer graphene targets are presented. Proton energy loss shows an unexpectedly high value as compared with measurements in amorphous carbon and carbon nanotubes. Furthermore, we observe a classical linear behavior of the energy loss with the ion velocity but with...
We present a simple and cheap experimental setup that clearly shows how the colors of the white light spectrum after passing a prism do not recombine when emerging from an identical second prism, as it is still found in many references.
We present a simple and cheap experimental setup that clearly shows how the colors of the white light spectrum after passing a prism do not recombine when emerging from an identical second prism, as it is still found in many references.
Los animales (entre los cuales se encuentra el ser humano) emplean sensores fisiológicos para obtener información de su entorno. Entre ellos podemos encontrar sensores eléctricos, magnéticos, térmicos, químicos, mecánicos y ópticos, por mencionar algunos. Varios de estos sensores son compartidos, en mayor o menor medida, por diversos animales, aunq...
The use of proton beams in several modern technologies to probe or modify the properties of materials, such as proton beam lithography or ion beam cancer therapy, requires us to accurately know the extent to which the energy lost by the swift projectiles in the medium is redistributed radially around their tracks, since this determines several endp...
The nano-scale dispersion of ordered/disordered phases in semi-crystalline polymers can strongly influence their performance e.g. in terms of mechanical properties and/or electronic properties. However, to reveal the latter in scanning electron microscopy (SEM) often requires invasive sample preparation (etching of amorphous phase), because SEM usu...
Hadron therapy is a modern cancer treatment based on the interaction of proton or heavier ion beams with living tissue, whose purpose is the destruction of the malignant tumor cells producing minimal effects on the surrounding healthy tissue. To study the physical basis of the Relative Biological Effectiveness (RBE) of different projectiles, such a...
We have simulated the passage of proton beams, having energies E < 10 keV, through graphene targets, considering the case of few layer foils. For this purpose and for comparison, we implement Monte Carlo and deterministic semi-classical approaches to describe the interaction of protons with carbon atoms in graphene structures. Our results show that...
La realització d’experiments de física utilitzant noves tecnologies és sovint més atractiva per als estudiants que
els experiments convencionals. En aquest treball usem la targeta de so d’un ordinador per a mesurar el temps que
transcorre entre dos sons. Hem portat a terme dos experiments per a calcular l’acceleració de la gravetat, on hem
utilitza...
A proper
description
of
the propagation of a swift proton beam through biomaterials, accounting for the energy deposited as well as the geometrical evolution of the beam as a function of the target depth and nature, is a crucial issue in proton therapy. For this purpose, simulation is a very adequate tool, since the most relevant interactions that...
Resumen: Se presenta un procedimiento sencillo y barato, basado en la electrólisis del sulfato de cobre, para determinar el valor de la constante de Avogadro N A. Mediante la pesada independiente de la masa metálica que forma el depósito, en función del tiempo que dura la electrólisis, se obtienen resultados numéricos para N A en muy buen acuerdo c...
The ionization yield of ion tracks in polymers and bio-molecular systems reaches a maximum, known as the Bragg peak, close to the end of the ion trajectories. Along the path of the ions through the materials, many electrons are generated, which produce a cascade of further ionizations and, consequently, a shower of secondary electrons. Among these,...
The inelastic mean free path and the stopping power of swift electrons in relevant biomaterials, such as liquid water, DNA, protein, lipid, carotene, sugar, and ice are calculated in the framework of the dielectric formalism. The Mermin Energy Loss Function – Generalized Oscillator Strength model is used to determine the energy loss function of the...
Con las actividades prácticas recogidas en este libro, pretendemos que la asignatura de Física y Química resulte más atractiva a los alumnos, especialmente en las primeras etapas de su aprendizaje científico, y también esperamos animar al profesorado a diseñar prácticas inspiradas en esta filosofía del empleo de materiales caseros.
The most established approach for 'practical' calculations of the inelastic mean free path (IMFP) of low-energy electrons (~10 eV to ~10 keV) is based on optical-data models of the dielectric function. Despite nearly four decades of efforts, the IMFP of low-energy electrons is often not known with the desired accuracy. A universal conclusion is tha...
We present a study where the energy loss function of Ta2O5, initially derived in the optical limit for a limited region of excitation energies from reflection electron energy loss spectroscopy (REELS) measurements, was improved and extended to the whole momentum and energy excitation region through a suitable theoretical analysis using the Mermin d...
We have studied the radial dependence of the energy deposition of the secondary electron generated by swift proton beams incident with energies T = 50 keV–5 MeV on poly(methylmethacrylate) (PMMA). Two different approaches have been used to model the electronic excitation spectrum of PMMA through its energy loss function (ELF), namely the extended-D...
We have calculated the lateral spread of the dose distribution of protons in liquid water by means of the SEICS (Simulation of Energetic Ions and Clusters through Solids) code, which properly accounts for the electronic stopping force (including energy-loss straggling), multiple elastic scattering with the target nuclei, dynamical electron charge-e...
La Física y la Química son disciplinas que se han desarrollado gracias a una fructífera simbiosis entre teoría y experimentación. Pero en el proceso de enseñanza-aprendizaje de estas materias se suele descuidar, por diferentes motivos (económicos, estructurales, organizativos, etc.) la realización de actividades experimentales, a pesar del consenso...
We present a simple method for obtaining reliable angular and energy distributions of electrons ejected from arbitrary condensed biomaterials by proton impact. Relying on a suitable description of the electronic excitation spectrum and a physically motivated relation between the ion and electron scattering angles, it yields cross sections in rather...
Stopping cross sections of TiO2 films were measured for H and He ions in the energy intervals 200–1500 keV and 250–3000 keV, respectively, using the Rutherford backscattering technique. Theoretical calculations were performed by means of two versions of the dielectric formalism and a non-linear model. Good agreement is found between the present exp...
Authors of physics textbooks frequently use the deflection of a thin, vertically falling water jet by a charged balloon,1-3 comb,4-6 or rod7-9 as a visually appealing and conceptually relevant example of electrostatic attraction. Nevertheless, no attempts are made to explore whether these charged bodies could cause visible deformation of a horizont...
We present an analytical model to evaluate in a fast, simple and effective manner the energy delivered by proton beamsmoving through a cell model made of nucleus and cytoplasm, taking into account the energy carried by the secondary electrons generated along the proton tracks. The electronic excitation spectra of these subcellular compartments have...
Ion-beam cancer therapy is a promising technique to treat deep-seated tumors; however, for an accurate treatment planning, the energy deposition by the ions must be well known both in soft and hard human tissues. Although the energy loss of ions in water and other organic and biological materials is fairly well known, scarce information is availabl...
We study the energy deposited by swift proton beams on materials of biological inter- est, such as liquid water, DNA, and PMMA. An appropriate description of the target energy-loss function, which provides its electronic excitation spectrum, is obtained from available experimental optical data properly extended to non-vanishing momen- tum transfers...
Low-energy electrons play a prominent role in radiation therapy and biology as they are the largest contributor to the absorbed dose. However, no tractable theory exists to describe the interaction of low-energy electrons with condensed media. This article presents a new approach to include exchange and correlation (XC) effects in inelastic electro...
We present a manageable approach to include, within the context of optical-data models of the dielectric response function, exchange and correlation (XC) effects in inelastic electron scattering, thus, going beyond the standard random-phase approximation (RPA). The many-body local-field correction in its static limit, G (q), is employed to incorpor...
In this work we review and further develop a semiempirical model recently proposed for
the ion impact ionization of complex biological media. The model is based on the dielectric formalism, and makes use of a semiempirical parametrization of the optical energy-loss function of bioorganic compounds, allowing the calculation of single and total ioniz...
We present a semiempirical model for calculating the electron emission from any organic compound after ion impact. With the only input of the density and composition of the target we can evaluate ionization cross sections, using plausible approximations, which are in good agreement with experiments. Results for protons impacting in the most represe...
The depth-dose distribution of proton beams in materials currently used in dosimetry measurements, such as liquid water, PMMA or graphite are calculated with the SEICS (Simulation of Energetic Ions and Clusters through Solids) code, where all the relevant effects in the evaluation of the energy deposited by the beam in the target are included, such...
En este trabajo se ha realizado un estudio, basado en un análisis estadístico, para determinar si existe correlación entre los alumnos que siguen con regularidad programas televisivos de contenido científico y su actitud hacia la asignatura de Física y Química. Nuestro estudio se centra fundamentalmente en el espacio dedicado a los experimentos cie...
The simulation code SEICS (Simulation of Energetic Ions and Clus-
ters through Solids) has been used to calculate the depth-dose profile and the spatial distribution of proton beams incident in liquid water. SEICS combines Molecular Dynamics and Monte Carlo techniques, and considers the main interaction phenomena between a swift charged par- ticle...
The electronic stopping cross section (SCS) of Al2O3 for proton beams is studied both experimentally and theoretically. The measurements are made for proton energies from 40 keV up to 1 MeV, which cover the maximum stopping region, using two experimental methods, the transmission technique at low energies (~40–175 keV) and the Rutherford backscatte...
We use a simulation code, based on Molecular Dynamics and Monte Carlo, to investigate the depth-dose profile and lateral radial spreading of swift proton beams in liquid water. The stochastic nature of the projectile-target interaction is accounted for in a detailed manner by including in a consistent way fluctuations in both the energy loss due to...
The energy dissipation pattern of low-energy electron beams (0.3–30 keV) in multi-walled carbon nanotube (MWCNT) materials is studied by Monte Carlo simulation taking into account secondary-electron cascade generation. A quasi first-principles discrete-energy-loss model deduced from a dielectric response function description of electronic excitatio...
A short review of the dielectric approach used to describe the energy
deposited in liquid water by swift proton beams is presented. Due to the
essential role played by the electronic excitation spectrum of the
target, characterized by its energy loss function (ELF), we discuss in
detail the procedure to obtain a reliable ELF from experimental optic...
Se ha utilizado una pluma de ave para estudiar la difracción de la luz, tanto de forma cualitativa como cuantitativa. La medida experimental de la separación entre los puntos luminosos del patrón de difracción
obtenido con un puntero láser ha permitido determinar el espaciado entre las barbas y entre las bárbulas de la pluma. Los resultados obtenid...
We have evaluated the spatial distribution of energy deposition by proton beams in liquid water using the simulation code SEICS (Simulation of Energetic Ions and Clusters through Solids), which combines molecular dynamics and Monte Carlo techniques and includes the main interaction phenomena between the projectile and the target constituents: (i) t...
The energy-loss straggling of zirconia (ZrO2) and alumina
(Al2O3) has been experimentally determined for proton and
alpha-particle beams mainly by means of the Rutherford backscattering technique and in
some few cases using the transmission method. The incident energies of the projectiles
covers a wide range, from 200 keV up to 2000 keV for H+ and...
The effect of bulk and surface excitations to inelastic scattering in low-energy electron beam irradiation of multi-walled carbon nanotubes (MWNTs) is studied using the dielectric formalism. Calculations are based on a semiempirical dielectric response function for MWCNTs determined by means of a many-pole plasmon model with parameters adjusted to...