₁¹H+ - and ₂⁴He+ - induced M-shell x-ray-production cross sections for selected elements in the rare-earth region Page: 3,217
6 p.View a full description of this article.
Extracted Text
The following text was automatically extracted from the image on this page using optical character recognition software:
VOLUME 28, NUMBER 6
(H+- and 2He+-induced M-shell x-ray-production cross sections for selected elements
in the rare-earth region
R. Mehta, J. L. Duggan, J. L. Price, P. M. Kocur, and F. D. McDaniel
Department of Physics, North Texas State University, Denton, Texas 76203
G. Lapicki
Department of Physics, East Carolina University, Greenville, North Carolina 27834
(Received 1 July 1983; revised 17 October 1983)
The measurements of M-shell x-ray-production cross sections induced by IH+ and 2He+ ions are
compared to the first-Born-approximation and ECPSSR (energy loss, Coulomb-deflection effects;
perturbed-stationary-state approximation, with relativistic corrections) theories. Most of the report-
ed experimental data were measured in our laboratory and the other measurements were taken from
the literature. The data from our laboratory were for incident H+ and He+ ions in the energy range
from 0.25 to 2.5 MeV. The M-shell x-ray-production cross sections were measured for the following
thin targets: 59Pr, 60Nd, 63Eu, 64Gd, 66Dy, 67Ho, 68Er, 70Yb, and 72Hf. The data from the literature
were for protons and He+ ions in the energy range from 30 keV to 40 MeV. These data were for
the following elements: 54Xe, 59Pr, 60Nd, 62Sm, 63Eu, 64Gd, 65Tb, 66Dy, 67Ho, 68Er, 70Yb, 72Hf, 73Ta,
74W, 78Pt, 79Au, 80Hg, 82Pb, 83Bi, and 92U. The first-Born-approximation calculations of the ioniza-
tion cross section were made using the plane-wave Born approximation for direct ionization and the
Oppenheimer-Brinkman-Kramers approximation of Nikolaev for electron capture. The ECPSSR
theory of Brandt and Lapicki [Phys. Rev. A 23, 1717 (1981)] goes beyond the first Born approxi-
mation and accounts for the energy loss, Coulomb deflection, and relativistic effects in the
perturbed-stationary-state theory. The first Born approximation overpredicts all measurements.
The ECPSSR theory predicts the M-shell production cross sections correctly for Z2 > 70 and ener-
gies per ys > 0.25 MeV/z. In the rare-earth region the ECPSSR results lie above the data at higher
projectile energies and fall off below the data at lower energies.INTRODUCTION
In the last several years, a clearer picture of M-shell
ionization has been established due to more consistent ex-
perimental measurements and renewed theoretical effort.
The ECPSSR calculations1 have been extended recently2
to M-shell ionization. The ECPSSR approach, which is
based on the perturbed-stationary-state approximation,
goes beyond first-Born-approximation theory, i.e., the
plane-wave Born approximation (PWBA)3 for direct ioni-
zation to the continuum (DI) and the Oppenheimer-
Brinkman-Kramers (OBK) approximation of Nikolaev
(OBKN)4 for electron capture to the ion (EC). The
ECPSSR theory includes the considerations due to energy
loss, Coulomb deflection, and relativistic effects. Satisfac-
tory agreement between the predictions of ECPSSR theory
and the measured data has been found for M-shell ioniza-
tion by H+ and He+ ions for selected targets.5 Experi-
mentally, the availability of relatively high-resolution
Si(Li) detectors since the early 1970's has helped to im-
prove the precision of M-shell ionization measure-
ments.5-16 Uncertainties in the data have been reduced
by overcoming difficulties associated with the determina-
tion of the efficiency of the Si(Li) detector in the low-
energy region of M-shell x rays (0.8-4 keV). In addition,
the quality of the measurements has improved due to
elimination of low-Z contaminant backgrounds, whichhave 1-4-keV K-shell x rays that overlap the M-shell x-
rays' range. The literature for M-shell x-ray studies with
1'H and 4He+ ions indicates a lack of experimental data
especially in the rare-earth region. The primary difficul-
ties associated with M-shell x-ray measurements for ele-
ments in the rare-earth region are related to the low ener-
gies of the M-shell x rays (0.8-1.6 keV). The uncertain-
ties in the efficiency of the Si(Li) detector are large at
these energies. For some of the rare-earth elements, low-Z
contaminants come from the extraction process used in
production of rare earths. For targets of 58Ce, 59Pr, and
60Nd, the 11Na and 12Mg contaminant K-shell x rays inter-
fere with the M-shell x-ray spectrum. Silicon contamina-
tion produces K-shell x rays which overlap the M-shell x
rays of 71Lu and 72Hf.
Over the years, the M-shell x-ray region for Z2 2 79 has
been studied in more detail than any other region. The
ECPSSR predictions are in satisfactory agreement with
the measured data in the 0.3-2.6-MeV range for both
1H+ and 4He+ ions.5 Detailed studies are not available
for lighter rare-earth targets. The work that is available
has uncertainties greater than 15%. The recent interest in
the rare-earth region is not only to fill in the gaps in the
data, but also to investigate the nature of M-shell x-ray
production with energy and the target atomic number Z2.
The ECPSSR theory predicts a maximum in M-shell x-
ray-production cross section when plotted versus Z2 in the@ 1983 The American Physical Society
PHYSICAL REVIEW A
DECEMBER 1983
28 3217
Upcoming Pages
Here’s what’s next.
Search Inside
This article can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Article.
Mehta, R.; Duggan, Jerome L.; Price, J. L.; Kocur, P. M.; McDaniel, Floyd Del. (Floyd Delbert), 1942- & Lapicki, Gregory. ₁¹H+ - and ₂⁴He+ - induced M-shell x-ray-production cross sections for selected elements in the rare-earth region, article, December 1983; [College Park, Maryland]. (https://digital.library.unt.edu/ark:/67531/metadc139491/m1/1/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT College of Arts and Sciences.