Carbon K-shell x-ray and Auger-electron production in hydrocarbons and carbon oxides by 0.6-2.0-MeV protons Page: 3,658
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R. P. BHALLA, F. D. McDANIEL, AND G. LAPICKI
TABLE II. Measured carbon K-shell Auger-electron-production cross sections, KA (kb), by protons
of energy El. Absolute uncertainty is +16% and, at a given energy, relative uncertainty from gas to
gas is 5%.
absolute value of the x-ray cross sections is + 14%; it is
caused by uncertainties associated with the determination
of solid angle and path length (5%), transmission of the
window (5%), particle-scattering spectra (4%), Ruther-
ford differential cross section due to uncertainty in
scattering angle (10%), and x-ray yield (3%). Similarly,
the uncertainty in the absolute value of the Auger-electron
cross sections is estimated to be 16%.
IV. X-RAY AND AUGER-ELECTRON-PRODUCTION
To reduce relative experimental errors to + 5%, we have
interchanged target gases keeping the beam energy con-
stant. The measured x-ray, cKX, and Auger-electron,
UKA , production cross sections are listed in Tables I and
II, respectively; absolute uncertainties in these cross sec-
tions were, correspondingly, 14% and 16%.
Experimental molecular carbon K-shell x-ray cross sec-
tions are plotted in Fig. 2. Almost independently of the
projectile energy, x-ray cross sections decrease by as much
0.6 1.0 1.4 1.8 2.2
PROTON ENERGY (MeV)
FIG. 2. K-shell x-ray-production cross sections in hydrocar-
bons and carbon oxides as listed in Table I. Relative uncertain-
ties are +5%.
as almost 30% once CH4 is replaced with oxides. This
trend is comparable to observations of Harrison et al.1
who used an electron beam instead of protons and found a
35% decrease in the relative x-ray yields from CH4 to CO.
Figure 3 gives a comparison of our carbon K-shell x-ray
cross sections for methane with those of Langenberg and
van Eck.11 Data of Khan et al.9 for thick carbon foils
and of Bissinger et al. o0 as well as of Langenberg and van
Eck11 for thin carbon foils are also shown for comparison.
Carbon K-shell Auger-electron cross sections, listed in
Table II, are displayed in Fig. 4 as a function of the pro-
ton energy. Similarly, as found for the x-ray cross sec-
tions but not to such a large degree, a 16% drop in these
cross sections occurs when CO is substituted for CH4. We
note a decrease of about 10% from CH4 to C2H2 which is
comparable with the 8% change seen by Toburen.7 We
observe also that our CO2 cross sections are 23% lower
than in CH4 while Toburen7 found only an 11% decrease.
K Khan et al. (1965) thick carbon
B Bissinger et al. (1976) thin carbon
3.0 L Langenberg and van Eck (1976) thin carbon
L' Langenberg and van Eck [1976) methane
B B *This work methane
S K K
_L L K K
0.6 1.0 1.4 1.8 2.2
PROTON ENERGY (MeV]
FIG. 3. K-shell x-ray production cross section in CH4 as list-
ed in Table I and as measured in Ref. 11. Data generated in
thick (Ref. 9) and thin (Refs. 10 and 11) solid-carbon targets are
displayed for comparison. Absolute uncertainties for the data of
this work are + 14%.
I I I I . I I
* CH4 methane
a n-C4H10 normal butane
A i-C4H10 isobutane -
O C6H6 benzene
* C2H2 acetylene
* CO2 carbon dioxide
o CO carbon monoxide
* 0 A A6 Q
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Bhalla, R. P.; McDaniel, Floyd Del. (Floyd Delbert), 1942- & Lapicki, Gregory. Carbon K-shell x-ray and Auger-electron production in hydrocarbons and carbon oxides by 0.6-2.0-MeV protons, article, May 1, 1987; [College Park, Maryland]. (digital.library.unt.edu/ark:/67531/metadc139493/m1/4/: accessed October 17, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT College of Arts and Sciences.