L-shell X-ray production by 2-12 MeV carbon ions in fifteen selected elements from copper to lead

Abstract

L-shell X-ray production cross sections for 29Cu, 31Ga, 32Ge, 35Br, 39Y, 42Mo, 47Ag, 50Sn, 57La, 60Nd, 64Gd, 67Ho, 70Yb, 79Au and 82Pb were measured for carbon ions in the 2-12 MeV energy range. The copper to yttrium data were previously measured using a Si(Li) detector with a beryllium window, while the molybdenum to lead X-rays were counted with a windowless Si(Li) detector, whose efficiency was determined by various normalization techniques. The measured X-ray cross sections are compared to predicted X-ray cross sections from the first Born and the ECPSSR theories. Using single-hole fluorescence yields, at low projectile velocities the first Born approximation overpredicts the data by as much as one order of magnitude while the ECPSSR theory at worse underestimates the data by about a factor of four. For the highest projectile velocities relative to target L-shell electrons, both theories converge toward the data to almost within experimental uncertainties. After modifying the fluorescence yield to account for multiple outer-shell ionization, the ECPSSR theory is brought into better agreement with the data for light targets but still overestimates the data for heavier targets. Also, the 2 MeV measurements using doubly ionized carbon ions are still significantly underestimated by the ECPSSR theory even after accounting for multiple ionization. Our multiple ionization correction assumes that the target foil thickness is thin enough to insure single collision conditions. However, in order to obtain acceptable signal-to-noise ratios, the target foils used in this experiment were too thick to provide single collision conditions. For thicker foils, ions are stripped inside the target resulting in an appreciable fraction of higher charge states that enhance the ionization of outer shells and the effective fluorescence yields. This effect could account for the remaining discrepancy between the ECPSSR theory and the data.

Effects of multiple ionization and intrashell coupling inL-subshell ionization by heavy ions

“…[26], replacement of the projectile atomic number Z 1 with its charge state q, the probability P of ionizing an outer shell electron is calculated according to Eq. (A3) of Ref.…”

M-shell x-ray production cross section measurements in Pb and Bi due to the impact of protons and nickel ions

“…A comparison of the M x-ray cross section measurements of Pb and Bi of earlier workers with the corresponding theoretical values indicates that there is a good agreement between the experimental results and the PWBA theory for protons and 4 He + ions (Busch et al 1973, Gowda andPowers 1985). Some of the other workers (Mehta et al 1982, de Castro Faria et al 1983, Price et al 1988, Pajek et al 1990a have, however, observed that the first Born theory always tends to over-predict the cross sections at all energies for protons and the other incident ions such as 3 He + , 4 He + and Be + , while the ECPSSR theory has been found to give the best overall description, although it tends to under-predict the data at very low energies (< 1 MeV). For C-, O-and F-ion impact the ECPSSR theory has been found to give good agreement with the experimental data while the first Born theory over-predicts the cross sections at all the measured energies , Andrews et al 1987.…”

“…Andrews et al (1987) have reported the M-shell x-ray production cross sections in Pb by 25 MeV 12 C q+ (q = 4, 5, 6) and by 32 MeV 16 O q+ (q = 5, 7, 8) ions. In two different measurements, Mehta et al (1982Mehta et al ( , 1983 measured the M x-ray production cross sections in Pb and Bi bombarded by protons and 4 He + ions of 0.3-2.6 MeV and by fluorine ions of charge states 4, 5, 6, 8 and 9 and energies of 25, 27 and 35 MeV. de Castro Faria et al (1983) have measured the M-subshell ionization cross sections of Pb and Bi by protons impact over the energy range 0.3-4.0 MeV while Price et al (1988) have reported the M-shell x-ray production cross sections for 9 Be + ions of energies 0.5-2.5 MeV incident upon Pb and Bi targets.…”

“…It is clear from the literature survey that most of the authors have studied M-shell ionization with protons, He ions, α-particles and other heavy ions (Be, C, O and F) at limited energies and that no data are available for heavier ions. Further, most of the authors have reported the total M-shell x-ray production cross sections (Busch et al 1973, Thornton et al 1974, Ishii et al 1975, Sera et al 1980, Mehta et al 1982, Gowda and Powers 1985, Andrews et al 1987, Price et al 1988,, Bienkowski et al 1990, Pajek et al 1990a and only de Castro Faria et al (1983) have measured the cross sections of different M x-ray lines (e.g. M 5 N 7 , M 4 N 6 , M 3 N 5 , M 3 O 5 , M 2 N 4 and M 1 O 2,3 + M 1 P 2,3 ) of Pb and Bi by proton impact.…”

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

“…While PIXE originated and continues using light ions such as protons or alphas [6][7][8][9][10][11][12][13][14][15][16],there is an increasing interest to use heavy ions for PIXE analysis due to higher cross sections and thereby better sensitivity [17]. While discrepancies between theories and experiment were attributed to multiple ionization even with protons [18], multiple-ionization effect has been known for decades in L-shell ionization by heavier ions [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34]. However this effect is still rarely addressed for the x-ray emission elemental analysis in the aftermath of ionization by such ions.…”