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U N T E E D S T A L E S A T o M I c E N E R G V C O M M T S S I O N
º cºro
SPALLATION PRODUCTS OF ARSENIC witH 190-MEv DEUTERONs
by
H. H. Hopkins, Jr.,
July 79 1919 … --> ; : . . . . A ºf
University of California.
Radiation Laboratory
oted data
This document, Conat, ins; no rºšt.
gy Act of 1916.
ſº.
as defined by the Atomic Energy. A
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This copy is regroduced by direct photograph
from copy as Submitted. to this office a
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Technical Information Branch, Oak Ridge Extension
AEC, Oak Ridge, Tenn. 9-19-49-–200-A8945
RSITY OF MICHIGAN
Illuli. Ill
O15 O8647 7596
SPALLATION PRODUCTS OF ARSENIC WITH 190-Mev DEUTERONS
H. H. Hopkins, Jr.,
Department of Chemistry and Radiation Laboratory
University of California, Berkeley, California
July 7, 1949
Recent invostigations" of the nuclei formed when arsenic is bombarded with
190-Mev deuterons in the 184-inch cyclotron have been extended.
The target material consisted of twice sublimed arsenic. Spectrographic
analysis” showed no impurity in sufficient quantity to account for the formation
of any of the isotopes reported here with the observed yields.
The use of improved chemical separations and counting techniques has enabled
the identification of 33 nuclear species among the elements from chromium through
selenium. Table I lists the isotopes identified, the observed and literature
half-lives”, and the yields relative to that of As”. Since some of the yield
figures depend on the extent of electron capture, the percentage of electron
capture used in the yield calculation is indicated after the yield figure in
parentheses. The yields reported here are all accurate to within a factor of
two and most are accurate to within 30%. The uncertainties lie in the electron-
capturing ratios and counting efficiencies.
Table I contains two changes in isotope assignment differing from those
previously revorted.* The 44-minute selenium and 52-minute arsenic daughter are
placed at mass 70 since careful separtions revealed no active germanium daughter.
The 40-hour german.ium cannot be found when germanium is chemically separated from
the 60-hour As71, so is assigned to mass 69, in agreement with the work of Pool.4
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Tabl
Iso e l
topes Produced by 7
S 5 4-
33% + D" (190 Mev)
Isotope *
y
3.3% pe Lit
§§ š. l . Half-Life?
; : , K ; : Obs, Half-Life Y:
B* 9, 5 d So 120 days Y: eld Rel. As'
33As; + 㺠6.7 hrs 0.1 .As72 (5)
As73 g",8" ſºlº 5.7 days Ö. 4 (100%)
ºff 17. 5 d ~sº ,27 ſº
# * § 3...” Ile 3.67%)
jo # . 19 days 0.00/.
8* 60 : (long l. 2
325e. # #. 26.7 hrs ** **
Geó9 #. 69 #: Q l,00
; : ; #: ;”
§§ 3. ;" hrs. ll day Oel
© st (?) 23 .." 40 º 2
31% 140 : 250 dºs 6. º
§§ { +. ~#: §§º
; : :* # *
36% $ 3. *::: 70 min. O. C.
Zná9m 8- I’S e 30 hrs. 5. º
Zn35 I.T., 49 hr 9 hrs .
Zn33 K 13. 3 : (9 #º
Znó2 * ; d;" ~; .56 (~70%)
290 67 \ ...; #:...". º
§4 B. J'S 9 ; min, º,
; fºr #: 0 hrs., O, O2 sº
Cu6l ;: #: º: 61 hrs 6.002(6)
~, Il , l e.
23; B- 3.4 hrs , #2,” ;
tº {{&sks k h \º • 20
Ni37 ;: :*::: 3. 3 hrs. §ſº
2:09: 36 º: : hrs. 0.03
Co38 3. 0 ; : C. 0006
Co55 ;: #".” i"Se C, OO30
18 days l, 83 l O. OOOO3
2éFe?? 8- • 2 hrs. icng *I'S e o &
:-- 46.3 ~18 hrs. ;
25 ºn: 8. . 3 day's Ö. § (~85%)
Mn st 2 46 days 69 O2
24Crº , K : hrs. O Ö{}
CrA9 K .8 days ; hrs , Cô5
* g &
Yle 25 days .0003(~65%)
Ö 69 2(100%)
0,00006
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It is reasonable to assume that stable nuclei are formed in the spallation
process with yields not far different from those of the adjacent isotopes. On
this basis Vre assign a yield to each isotope which we cannot observe, following
the trends apparent among the observed isotopes. The resultant yield pattern ean
be described as follows:
(1) For each element belor arsenic, the yields of the isotopes increase
towards the line of nuclear stability.
(2) For each mass number the yields of isobars increase towards the line of
stability.
(3) The lover the atomic number, the lower becomes the total yield of a given
element.
From a consideration of the Q. values of the reactions and the energy necessary
for coulombic barrier penetrations, we conclude:
(1) Reactions leading to arsenic, germanium, and gallium isotopes are mostly
non-capture excitation reactions, in which only a fraction of the deuteroſis
energy is imparted to the nucleus. These comprise >90% of all the reactions
(2) Less likely processes involving preliminary capture of the deuteron lead
to isotopes of lower lying elements.
(3) The formation of nuclear species lower than Fe?" involves the emission of
one or more alpha-particles. Such reactions occur - 1% of the time.
This work was performed under tho auspices of the United States Atomic Energy
Commission.
References
H. H. Hopkins, Jr. and B. B. Cunningham, Phys. Rev. 73, 1406 (1948).
Analysis performed by Mr. John Conway.
} Taken from G. T. Seaborg and I. Perlman, Revs. Mod. Phys. 20, 585 (1948).
)
)
D. A. McCown, L. L. Woodward and M. L. Pool, Phys. Rev. 74, 1311 (1948).
Absolute yield of As72: 0.02 barns.
Observed radiation only of daughter. g
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