ECPSSR Theory Research Articles

ERCS24: An updated version of the ERCS08 program for calculations of the cross sections for atomic electron removal based on the ECPSSR theory and its variants

ERCS24: An updated version of the ERCS08 program for calculations of the cross sections for atomic electron removal based on the ECPSSR theory and its variants

Experimental low velocity proton and 28Siq+ induced X-ray production cross sections for select elements within 24 ≤ Z ≤ 83

Particle Induced X-ray Emission (PIXE) spectroscopy is an effectively well-established analytical technique in the low projectile mass (Z < 3) regime. This is in part due to the availability of fairly accurate theoretical models of fundamental interaction parameters such as the X-ray production cross section (XPCS). Continual development of widely used theoretical models such as the ECPSSR theory with adapted corrections in the United Atom limit (UA), Electron Capture (EC) and Multiple Ionisation (MI); requires a rich database of experimental X-ray production cross sections. Beyond the scope of proton PIXE, validated reliable theoretical models may be useful for the accurate approximation of heavy ion induced X-ray production cross sections for Heavy Ion PIXE. This requires persistent efforts aimed at contributing to the currently sparse heavy ion induced X-ray production cross section database. In this work, we report on a new experimental dataset of low energy XPCS in the 0.3 MeV/u – 1.0 MeV/u ion velocity range in Cr, Ni, Ge, Mo, Sn, W, Au and Bi due to proton and 28Siq + ion impact, with an aim at enriching and updating the current database.

K-shell x-ray of Al produced by collisions of ions with near Bohr velocities

X-ray emissionproduced by highly charged ions with the energy range near the Bohr velocity involves complicated atomic process. However, duo to the limitation of experimental conditions, the relevant researches are nearly absent. It is unclear whether the existing theory is applicable in such an energy range. This needs further exploring. In the present work, K X-ray spectra of Al excited by H&lt;sup&gt;+&lt;/sup&gt;, He&lt;sup&gt;2+&lt;/sup&gt; and highly charged heavy ions I&lt;sup&gt;22+&lt;/sup&gt; and Xe&lt;sup&gt;20+&lt;/sup&gt; are investigated by using an Si drift X-ray detector in the energy range near the Bohr velocity. The X-ray production cross sections are extracted from the X-ray counts and compared with the theoretical simulations from PWBA, ECPSSR and modified BEA model. It is indicated that the cross section increases with the augment of projectile energy. With the same incident energy per nucleon, the cross section induced by highly charged heavy ions is a factor of about 10&lt;sup&gt;4&lt;/sup&gt; larger than that by light ions . With the impact of H&lt;sup&gt;+&lt;/sup&gt; and He&lt;sup&gt;2+&lt;/sup&gt; ions, the K-shell electrons are mainly knocked off through the direct Coulomb ionization, and the X-ray emission cross section can be well predicted by ECPSSR theory. For the bombardment of highly charged heavy ions I&lt;sup&gt;22+&lt;/sup&gt; and Xe&lt;sup&gt;20+&lt;/sup&gt;, except for the Coulomb ionization, the orbital electrons can also be excited by electron capture. The BEA simulation after being modified by both Coulomb repulsion and effective charge can well predict the x-ray production cross section.

K-shell X-ray of Al produced by collisions of ions with near Bohr velocities

X-ray emissionproduced by highly charged ions with the energy range near the Bohr velocity involves complicated atomic process. However, duo to the limitation of experimental conditions, the relevant researches are nearly absent. It is unclear whether the existing theory is applicable in such an energy range. This needs further exploring. In the present work, K X-ray spectra of Al excited by H&lt;sup&gt;+&lt;/sup&gt;, He&lt;sup&gt;2+&lt;/sup&gt; and highly charged heavy ions I&lt;sup&gt;22+&lt;/sup&gt; and Xe&lt;sup&gt;20+&lt;/sup&gt; are investigated by using an Si drift X-ray detector in the energy range near the Bohr velocity. The X-ray production cross sections are extracted from the X-ray counts and compared with the theoretical simulations from PWBA, ECPSSR and modified BEA model. It is indicated that the cross section increases with the augment of projectile energy. With the same incident energy per nucleon, the cross section induced by highly charged heavy ions is a factor of about 10&lt;sup&gt;4&lt;/sup&gt; larger than that by light ions . With the impact of H&lt;sup&gt;+&lt;/sup&gt; and He&lt;sup&gt;2+&lt;/sup&gt; ions, the K-shell electrons are mainly knocked off through the direct Coulomb ionization, and the X-ray emission cross section can be well predicted by ECPSSR theory. For the bombardment of highly charged heavy ions I&lt;sup&gt;22+&lt;/sup&gt; and Xe&lt;sup&gt;20+&lt;/sup&gt;, except for the Coulomb ionization, the orbital electrons can also be excited by electron capture. The BEA simulation after being modified by both Coulomb repulsion and effective charge can well predict the X-ray production cross section.

X-ray production cross sections induced by carbon ions

The K-shell of Ti, Cr, Cu, Zn, Zr, Nb, Mo, Ag, Cd, In, Sn, Sb x-ray production cross sections, L-shell x-ray production cross sections of Zr, Nb, Mo, Ag, Cd, In, Sn, Sb, Ta, W, Pb, Bi and M-shell x-ray production cross sections of Ta, W, Pb and Bi were measured for 9.6–19.2 MeV 12C2+ ions and are compared to the ECPSSR and PWBA theories. The cross sections were calculated through the Rutherford backscattering cross section, which can be calculated from the Rutherford formula. The ECPSSR and PWBA calculations were performed with the ISICS11 code.

Mg K-shell x-ray emission induced by various ions

Mg K-shell x-ray production cross sections have been investigated for the impact of H+, He2+ and highly charged heavy ions Xe20+ and Eu20+ in the energy range near the Bohr velocity. The x-ray production cross sections were extracted from the yield and compared with various theoretical calculations. It is found that, with the same incident energy per nucleon, the cross section induced by light ions is lower than that produced by highly charged heavy ions by a factor of about 104. With the impact of H+ and He2+ ions, the x-ray emission cross section can be well predicted by ECPSSR theory. However, for the bombardment of highly charged heavy ions, the BEA calculation, corrected both by Coulomb repulsion and effective nuclear charge, results in a good estimation to the experimental data.

Measurement of 12Cq+ and 35Clq+ ion induced X-ray production cross sections in V, Zr and Sn metal oxide films at 0.1 MeV/u - 1.0 MeV/u energies

Experimental X-ray production cross sections in matter are key to fundamental ion-atom interaction studies. They also find practical applications such as in the advancement of ion beam materials analysis techniques like Particle Induced X-ray Emission (PIXE) spectroscopy. Experimental work shows that heavy ion probes induce higher X-ray yields in target atoms compared to light ions of the same velocity. This, in principle, implies higher sensitivity for PIXE analyses performed using heavy ions (Heavy Ion PIXE). There is therefore need for substantial experimental data to improve existing theoretical models that describe X-ray production due to heavy ion-atom collisions. This article presents measurements carried out to determine K-shell X-ray production cross sections in vanadium (V) due to 12Cq+ ions, and L-shell X-ray production cross sections in zirconium (Zr) and tin (Sn) due to 12Cq+ (q = 2, 3) and 35Clq+ (q = 3, 5, 6, 7) MeV ion beams within a velocity range of 0.1 MeV/u - 1.0 MeV/u. Measured cross sections are compared with predictions by the modified Plane Wave Born Approximation (PWBA) and the ECPSSR theory. Observed agreements and discrepancies between experiment and theory are discussed in terms of the underlying ionisation mechanisms.

Proton induced L-shell cross-sections for some post-transition metals: A comparison of ECPSSR and SCA models

The L-shell ionisation and X-ray production cross-sections of some post-transition elements: In, Sn and Tl, induced by protons of energies 1 MeV–4 MeV, have been calculated. The targets considered have few experimental cross-sections, for indium and tin, while thallium has no existing cross-section values in the database due to its radioactive and toxic nature. The cross-sections for the targets were obtained using computer codes based on the ECPSSR and SCA theories; and were subsequently validated using lead and bismuth targets whose experimental values are known within this energy range. The comparison of the experimental and calculated cross-sections showed that both models are in good agreement within certain proton energy region. However, above 2 MeV, the ECPSSR models should be employed. For the case where the SCA model is to be employed, the energy loss and Coulomb deflection factors should be taken into account.

Multiple ionization effect in Dy, Ho and Er at low proton energy

SynopsisThe L shell X-ray production cross sections for elements (Z = 66, 67 and 68) at three different low proton energies i.e. 260, 280 and 300 keV have been investigated. Calculations are based on the ECPSSR model and its modified form i.e. ECPSSR-UA model. During calculations with ECPSSR theory, a significant phenomenon known as multiple ionization (MI) has been included. Theoretically calculated values are compared with the experimental values. The calculations with ECPSSR-MI shows improved results.

X-ray production cross sections induced by neon ions

Cross sections for K, L, and M x-ray production in thin metal films excited by neon ions with projectile energies from 16 to 32 MeV for the elements from Ti to Bi were measured. The X-ray production calculations were performed through the Rutherford backscattering cross sections, which can be obtained from the Rutherford formula with high accuracy. The obtained results were compared with the predictions of the ECPSSR and PWBA theories calculated using the ISICS program.

PIXE-measurement of Kα X-ray production cross sections for 1-MeV C+-ions in thick samples of Si, Fe, Cu and Zn

Particle-Induced X-ray Emission (PIXE) using heavy ions proved to be an alternative with respect to PIXE using light protons due to relatively large cross sections. In this work we explored the capabilities of PIXE with using singly-charged carbon ions at relatively low energy of 1 MeV (or 83 keV/amu) to measure Kα X-ray production cross sections. The measurement was performed for thick samples of Si, Fe, Cu and Zn, using the standard 2-MeV proton-induced cross sections as the reference. For the measurement from thick samples, we adopted a special multi-slabs method in the calculation by considering the sample thickness effect. The effective ion range was divided into a number of thin slabs in which the energy dependent cross section and the thickness dependent X-ray transmission were varied. The paper describes details of the measurement principle and method and reports the result. The resulting data obtained from the present work were compared with those from the PWBA and ECPSSR theories, the simple thin-film method and the measurement of thin film samples and discussed for the validity of our result.

Calculation of L-shell ionisation and x-ray production cross sections for some trans-uranium elements induced by protons

L-shell ionisation and x-ray production cross sections of trans-uranium elements: Np, Pu and Am, induced by protons of energies 5.00–20.00 MeV, have been calculated. The cross sections for the targets were obtained using computer codes based on the ECPSSR theory. Due to the lack of experimental data of the targets considered, in view of their radioactive, toxic and unstable nature, the calculated cross sections were subsequently validated. This was achieved using the computer codes to evaluate the ionisation and x-ray production cross sections of Uranium induced by protons of energies in the 1.00–20.00 MeV range. This study also showed that the relative x-ray line intensities associated with the ionisation and x-ray productions of the targets considered are dependent on protons energies.

L-shell X-ray production cross sections in metal oxide thin films due to 12C, 16O and 28Si ion beams at MeV SIMS energies

Successful co-implementation of different heavy ion beam nuclear analytical techniques such as heavy ion PIXE, ERDA, MeV SIMS and RBS hinges on the availability of accurate databases of fundamental ion beam-matter interaction parameters. We report on measurements carried out to determine L-shell X-ray production cross sections in 101Ru and 181Ta due to 12C, 16O and 28Si projectile ions in the 0.2 MeV/u–1.0 MeV/u energy range. Experimental data is compared to calculations by one of the most widely implemented X-ray ionisation theories in PIXE analyses – the ECPSSR theory in its modified United Atom (UA) version. Results show fairly good agreement between experiment and theory for the 181Ta target atoms, with the level of agreement improving as the Zion/Ztarget ratio decreases and as beam energy increases. For 101Ru target atoms theoretical predictions tend to underestimate experimental data and the discrepancies increase with projectile mass and decreasing energy. The contribution of projectile electron capture (EC) to the measured X-ray production cross sections is also considered in the data analysis and discussion.

L shell X-ray production cross sections for Sr and Mo by proton impact

Total L X-ray production cross sections were measured for Sr and Mo by proton impact. Proton energies ranged from 200 keV to 3 MeV. K shell cross sections of Ti and Cu samples were obtained in order to normalize our results, bearing in mind that for those elements the cross sections have been vastly measured and modeled. The cross sections were obtained using the thick sample method and the results showed general agreement in the range of energies studied. The results obtained here for Sr and Mo are in well agreement with those predicted by the ECPSSR theory in the 500–3000 keV proton energy range. In the case of Sr and proton energies lower than 500 keV, the experimental results do not agree well to the calculated with ECPSSR, differing by values greater than 30%. This discrepancy may be due to an overstimation of the stopping power in oxides or secondary emissions that are not negligible in this energy range. All measured spectra were fitted by a novel open software for PIXE semi-quantitative analysis that take into account several physical phenomena related to X-ray production, absorption and detection.

Considerations about projectile and target X-rays induced during heavy ion bombardment

Abstract In this work we present some results concerning the X-rays emitted by heavy ions during target bombardment. In this case, Cl4+ and Cl5+ ions with energies from 4 MeV to 10 MeV were employed to irradiate vitreous carbon planchets. Moreover, total X-ray production cross sections of titanium X-rays induced by chlorine ions were obtained as well for the same energy range. Only inner shell transitions were considered in the present work. The titanium target consisted of a thin film deposited over vitreous carbon planchets. The results indicate that the projectile X-ray yields increase as a function of the bombarding energy for the present energy range. Effects due to projectile charge state appears to be of minor importance at these low ion velocities. It is shown that a simple exponential function can represent the continuum background of such complex spectra. The chlorine transition rates Kβ/Kα obtained from chlorine acting as a projectile interacting with a carbon target are about half the value when compared to the chlorine Kβ/Kα ratios obtained when a LiCl target is bombarded with C+ and C3+ ions with energies from 2 MeV to 6 MeV. As far as the total X-ray production cross sections of Ti induced by chlorine ions are concerned, the ECPSSR theory underestimates the Ti total X-rays production cross sections by several orders of magnitude. The role of electron capture and possible mechanisms responsible for these effects are discussed.

Electronic wave function and binding effects in M-shell ionization of gold by protons

Abstract The measured M-X-ray production cross sections for protons, which are used in the particle induced X-ray emission (PIXE) technique, are systematically underestimated for low impact energies by the ECPSSR and ECUSAR theories. These theories, which are based on the plane wave Born approximation (PWBA) and use the screened hydrogenic wave functions, include corrections for the projectile Coulomb deflection and electron relativistic and binding effects. In the present paper, in order to interpret the observed disagreement at low impact energies, the systematic calculations of the M-shell ionization cross sections for gold were performed using the semiclassical (SCA) and the binary encounter (BEA) approximations in order to identify a role of the electronic wave function and electron binding effects. In these calculations the different wave functions, from nonrelativistic hydrogenic to selfconsistent Dirac-Hartree-Fock, were considered and the binding effect was treated within extreme separated- (SA) and united-atoms (UA) limits. The results are discussed in details and the observed discrepancies are attributed to inadequate description of the electron binding effect at the lowest impact energies for which the molecular approach is required.

K-, L- and M-shell X-ray productions induced by krypton ions in the 0.8–1.6 MeV/amu range

The K-, L- and M-shells X-ray production cross sections induced by krypton ions for a range target elements from Ti to Bi were measured. In the experiments the thin films were irradiated by 84Kr particles with projectile energies of 67.2, 84.0, 100.8, 117.6 and 134.4MeV. An approach based on the use of Mo grid with 500nm deposited bismuth layer as a beam monitor was developed to determine the amount of particles delivered on the sample. The efficiency of the X-ray detector was determined using the calibration radioactive sources. The experimental results were compared to the predictions of the ECPSSR and PWBA theories calculated with the ISICS code.

L shell x ray production in high-Z elements using 4–6 MeV/u fluorine ions

L shell line and total x ray production cross sections in 78Pt, 79Au, 82Pb, 83Bi, 90Th, and 92U targets ionized by 4–6MeV/u fluorine ions were measured. These cross sections are compared with available theories for L shell ionization using single- and multiple-hole fluorescence and the Coster-Kronig yields. The ECPSSR and the ECUSAR theories exhibit good agreement with the measured data, whereas, the FBA theory overestimates them by a factor of two. Although for the F ion charge states q=6–8 the multiple-hole atomic parameters do not significantly differ from the single-hole values, after an account for the multiple-holes, our data are better in agreement with the ECUSAR than the ECPSSR theory.

Cross sections of X-ray production induced by C and Si ions with energies up to 1 MeV/u on Ti, Fe, Zn, Nb, Ru and Ta

X-ray production differential cross sections induced by C and Si ions with energies from 1MeV/u down to 0.25MeV/u, produced by the CMAM 5MV tandem accelerator, have been measured for thin targets of Ti, Fe, Zn, Nb, Ru and Ta in a direct way. X-rays have been detected by a fully characterized silicon drift diode and beam currents have been measured by a system of two Faraday cups. Measured cross sections agree in general with previously published results. The ECPSSR theory with the united atoms correction gives absolute values close to the experimental ones for all the studied elements excited by C ions and for Ta, Nb and Ru excited by Si ions. For Ti, Fe and Zn excited by Si, the matching with theory is poor since even the ionization cross section is below the measured data.

K-, L- and M-shell X-ray productions induced by oxygen ions in the 0.8–1.6 MeV/amu range

The X-ray production cross sections induced by oxygen ions with projectile energies from 12.8 to 25.6MeV for the elements from Al to Bi were measured. The applied approach is based on calculation of X-ray production cross sections through the cross section of Rutherford backscattering, which can be calculated with high accuracy using the Rutherford formula. The experimental results are compared to the predictions of ECPSSR and PWBA theories calculated with the ISICS code.