PIXE2010: Proton/alpha Ionization (k, l, m shell), Tabulated Cross Section Library.
IONXSEC: auxiliary software to print out data.
INFN, Sez. Genova, Italy; Max-Planck-Institut f. extraterrestrische Physik and MPI Halbleiterlabor, Germany; Creighton University, Illinois, USA; CNES, Toulouse, France; INFN, Laboratori Nazionali di Frascati, Italy; Berkeley University, USA; and Jo˛ef Stefan Institute, Ljubljana, Slovenia
The physics aspects associated with PIXE involve the creation of a vacancy in the shell occupancy due to ionization and the emission of x-rays from the following atomic de-excitation. Various theoretical and empirical models are available in the literature to describe ionization cross sections for different interacting particles, as well as compilations of experimental data. The PIXE2010 data library is based on the developments described in Pia et al. [[1]]. It provides tabulations of ionization cross sections for proton and α (alpha) particle impact as a function of element, atomic (sub-) shell, and incident particle kinetic energy, for elements with atomic number from 1 to 92. This data library derives from software developments meant for use with the Geant4 [[2]] simulation toolkit. Nevertheless, the data library itself is independent from Geant4 and can be used in other software environments. Cross section values at a desired energy can be calculated by interpolation over the tabulated values.
The data can be useful to Monte Carlo simulation of PIXE or software systems for elemental analysis.
The data library contains cross section tabulations for K, L and M shell ionization based on various theoretical and empirical models. The models from which the data derive are described in detail in [1]; the most relevant related references are cited next to the models. The cross sections associated with theoretical models have been pre-calculated employing ISICSoo class [[3]], an object-oriented C++ implementation of latest version of ISICS [[4]]. The code and the documentation for ISICSoo class can be obtained from the authors. Theoretical cross section models include:
1. Plane Wave Born Approximation (PWBA) [3]
2. ECPSSR [3]
3. ECPSSR with United Atom correction (ECPSSR-UA) [3]
4. ECPSSR with corrections for the Dirac-Hartree-Slater nature of the K shell (ECPSSR-HS) [3]
5. ECPSSR with improvements to K shell cross section specific to high energy (ECPSSR-HE) [3]
The tabulations corresponding to theoretical calculations span the energy range between 10 keV and 10 GeV. Empirical cross section models for K shell proton ionization include the tabulations for protons documented in [[5]] and a more recent one [[6]]. An empirical cross section model for K shell ionization by α particles is based on the tabulations in [[7]]. Empirical cross sections for L shell ionization by protons are based on models by Miyagawa et al. [[8]], Sow et al. [[9]] and Orlic et al. [[10]]. The empirical models are tabulated consistently with their energy range of validity. Details about the accuracy of the cross section are reported in [1]; specifically, section V (pp. 3627–3639) is devoted to the verification and validation of the cross section models tabulated in the data library. Copies of [1] can be downloaded from http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=5341442 or can be requested from the contact person: M.G. Pia (MariaGrazia.Pia@ge.infn.it).
Data retrieval program “IONXSEC” is included in the package. The IONXSEC code may be used to print-out the PIXE2010 data, according the following options:
· choice of the element;
· choice of the impinging particle (alpha or protons);
· choice of the shell: k, l (l1, l2, l3), m (m1, m2, m3, m4, m5);
· choice of several proposed models for each shell;
· choice of the energy range.
Instructions about how to install and run the program can be found in the README file in the “ionxsec” folder.
Data are stored in files which make up a data library for PIXE simulation. Each cross section data set is stored as a separate file. The library is provided in computer independent ASCII format, which allows the data to be easily transported between computers. The entire library requires approximately 25 MB of storage. The data are divided into two main folders: a) proton folder and b) alpha folder. Each of these folders contains:
a) k folder; it contains a folder for each implemented model for K-shell ionization
b) l folder; it contains a folder for each implemented model for L-shell ionization
c) m folder; it contains a folder for each implemented model for M-shell ionization
Each model folder directory contains an ASCII file for each element; it appears as two columns listing energy values and corresponding cross section values. Energy and cross sections are given in MeV and mb, respectively. (D00246MNYCP00).
A few seconds are required to print the whole set of cross sections.
11. S. J. Cipolla, “The United Atom Approximation Option in the ISICS Program to Calculate K, L, and M-Shell Cross Sections from PWBA and ECPSSR Theory,” Nucl. Instrum. Meth. B, 261, 142–144 (2007).
12. W. Brandt and G. Lapicki, “Energy-Loss Effect in Inner-Shell Coulomb Ionization by Heavy Charged Particles,” Phys. Rev. A, 23, 1717–1729 (1981).
13. G. Lapicki, “The Status of Theoretical K-Shell Ionization Cross Sections by Protons,” X-Ray Spectrom. 34, 269–278 (2005).
14. G. Lapicki, “Scaling of Analytical Cross Sections for K-Shell Ionization by Non Relativistic Protons to Cross Sections by Protons at Relativistic Velocities,” J. Phys. B, 41, 115201 (2008).
15. Z. Liu and S. J. Cipolla, “ISICS: A Program for Calculating K-, L-, and M-Shell Cross Sections from ECPSSR Theory using a Personal Computer,” Comput. Phys. Commun., 97, 315–330 (1996).
16. S. J. Cipolla, “An Improved Version of ISICS: a Program for Calculating K, L, and M-Shell Cross Sections from PWBA and ECPSSR Theory using a Personal Computer,” Comput. Phys. Comm., 176(2), 157–159 (January 2007).
[1]. M.G.Pia, et al., “PIXE Simulation with Geant4,” IEEE Trans. Nucl. Sci., 56(6) 3614–3649 (December 2009).
Background Information
[2]. S. Agostinelli et al., “Geant4—A Simulation Toolkit,” Nucl. Instrum. Methods Phys. Res. A, A506(3) 250–303 (2003).
[3]. M. Batič et. al. ”ISICSoo: a Class for the Calculation of Ionization Cross Sections from PWBA and ECPSSR Theory,” submitted to Computer Physics Communications, April 2011.
[4]. S. Cipolla, “ISICS, 2010 version,” private communication: S. Cipolla, Creighton Univ., Omaha NE 68178.
[5]. H. Paul and J. Sacher, “Fitted Empirical Reference Cross Sections for K-shell Ionization by Protons,” Atom. Data Nucl. Data Tab., 42, 105–156 (1989).
[6]. A. Kahoul, M. Nekkab, and B. Deghfel, “Empirical K-shell Ionization Cross-Sections of Elements from 4Be to 92U by Proton Impact,” Nucl. Instrum. Meth. B, 266, 4969–4975 (2008).
[7]. H. Paul and O. Bolik, “Fitted Empirical Reference Cross Sections for K-Shell Ionization by Alpha Particles,” Atom. Data Nucl. Data Tab., 54, 75–131 (1993).
[8]. Y. Miyagawa et al., “Analytical Formulas for Ionization Cross Sections and Coster-Kronig Corrected Fluorescence Yields of the Ll, L2, and L3 Subshells,” Nucl. Instrum. Meth. B, 30, 115–122 (1988).
[9]. C. H. Sow et al., “New parameters for the Calculation of L Subshell Ionization Cross Sections,” Nucl. Instrum. Meth. B, 75, 58–62 (1993).
[10]. I. Orlic et al., “Semiempirical Formulas for Calculation of L Subshell Ionization Cross Sections,” Int. J. PIXE, 4(4) 217–230 (1994).
The ASCII data files are approximately 25 MB.
August 2011
KEYWORDS: PIXE, IONIZATION, CROSS SECTION, X-RAY