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Ames Laboratory ISC Technical Reports Ames Laboratory

6-22-1950

Radioactivities of germanium, arsenic, gallium and

zinc

Warren Heiman

Iowa State College

Adolf Voigt

Iowa State College

Follow this and additional works at:http://lib.dr.iastate.edu/ameslab_iscreports Part of theChemistry Commons

This Report is brought to you for free and open access by the Ames Laboratory at Iowa State University Digital Repository. It has been accepted for inclusion in Ames Laboratory ISC Technical Reports by an authorized administrator of Iowa State University Digital Repository. For more information, please contactdigirep@iastate.edu.

Recommended Citation

Heiman, Warren and Voigt, Adolf, "Radioactivities of germanium, arsenic, gallium and zinc" (1950).Ames Laboratory ISC Technical Reports. 10.

(2)

Abstract

Radioactivities were produced by the fast (pile) neutron bombardmant of germanium.. Chemical separations followed by decay and absorption measurements yielded the following results. Eleven-day Ge-71 decays with the emission of positrons with maximum energy of 0.65-Mev Ge-77 with 12 hour half-life emits 0.31 Mev gamma-rays. The half-life of As-77 i s 38.0 plus or minus 0.5 hours and it emits 0.68 Mev beta particles and two gamma rays. The following new gallium and zinc activities were observed, but not as signed definite mass numbers. A 14.5 day gallium activity emits beta particles with energies of 0.29 and 0.71 Mev, 34 Kev gamma rays and possibly X-rays; a 53 hour gallium activity gives off ' 1.9 Mev beta particles and 1.63 Mev gamma rays; a 14-day zinc activity decays 'Wi.th the emission of 2.1 Mev particles and 40 Kev gamma rays.

Disciplines Chemistry

(3)

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ISC -89 ''(.

...

RADIOACTIVITIES OF GERMANIUM~ ARSENIC, GALLIUM AND ZINC

By

Warren Heiman

Adolf Voigt

June

22, 1950

Iowa State College

(4)

PRINTED IN U.S.A.

(5)

ISC-89

Abstract

Radio activit i-es were produced by the fast (pile) neutron

bombard-mant of germanium.. Chemical separations followed by decay and

absorp-tion measurements yielded the following results., Eleven-day

ae

71

decays with the emission of posi trona with maximum energy of 0.65-Mev

Ge 77 with 12 hour half-life amits Oo3l,Mev gamma-rays. The half-life of

As 77 i s 38.,0

~

0.,5 hours and it emits 0.68 Mev

J'

-particles and two

IQ -rays. The fb llowing new gallium and zinc activities were observed,

but not assigned definite mass numbers.

A

14o5 day gallium activity

emits

f3

-particles with energies of 0.,29 and 0.71 Mev, 34 Kev (-rays

and possibly X-rays; a 53 hour gallium activity gives off' 1.9 Mev

f3

particles ani 1.63

Mev~-rays;

a 14-day zinc activity decays 'Wi.th the

emission of 2.,1 Mevfparticles and 40 Kev frayso

(6)

Radioactivities of Germanium, Arsenic, Gallium, and Zinc*

by Warren Heiman and Adolf Voigt

Introduction

The fast neutrons produced in fission have sufficient energy to

induce some reactions other than then,~ process most frequently o

b-served with the moderated neutrons used in pile bombardmentso In order

of increasing energy requirements and consequent lower probability the

n, p , n, ct_, and n, 2n reactions might be observedo The desired radi

o-activities can be found more readily if the thermal component of the

neutron spectrum is filtered outo Consequently cadmium wrapped samples

of materials are frequently irradiated in order to study these activitieso

Since the atomic number of germanium is low the positive particles,

the proton and the alpha particles, would not require too high an energy

to be ejected, hence, germanium was chosen as an element for studyo

Also it was felt possible that certain discrepancies in the reported

activities for ger~~nium could be corrected and certain new activities

might be produced~ By means of the fast neutron bombardment of germanium,

rather high specific activities may be obtained for the radioactive

isotopes of gallium, zinc, and arsenic, because the germanium may be

com-pletely separated from them by use of a special distillation apparatuso

The unstable nuclides possibly produced by these reactions would be

Zn 699 71, and 73 by n,~; Ga 70, 72, 73, 74, and 76 by n,p; Ge 69, 71,

and 75 by n,2n in addition to Ge 71, 75, and '17 by n,

r

o Daughter

pro-ducts could also be producedo

(7)

ISC-89 3

Chemical Procedure

Spectroscopically pure. one gr~ samples of GeOz were bombarded

with neutrons in the nuclear reactor of the Argonne National Laboratory.,

Each sample was contained in a silica tube which was wrapped with

ap-proximately 1/32 inch cadmium foil to absorb the thermal neutronso The

lengths of the bombardments varied from five days to two monthso

Upon receipt of a bombarded sample9 the radioactive Ge02 was

dis-solved in dilute NH4?H., This solution was then made strongly acid with

concentrated HClo Zinc9 arsenic9 and gallium carriers were then added

and the solution was transferred to a special apparatus for the

distilla-1

tion of GeC1 4 under an atmosphere of Cl2o The GeC1 4 was completely

re-moved by distillation and precipitated as GeS2.,

The solution remaining in the distilling flask contained arsenic,

galliums and zinc., The arsenic was precipitated from 9 N HCl as the

sulfideo The arsenic was filtered out and the filtrate contained

gal-lium and zinc. The filtrate was made 7 N in HCl and the gallium was

extracted with isopropyl ethero The galliumwas precipitated as Ga(OH) 3

and the zinc which remained in the aqueous phase was taken down as

ZnNH4P04o The procedure for gallium and zinc was modified in one of the

bombardments in order to detect any possible tin impurityo Tin was

added with the other carriers and subsequently separated by ether

extrac-tiono It was precipitated as Sn(OH) 4 after the separationo

Germanium

(8)

the samples arrived at .Ames had half-lives of 31 hours and ll days plus a

low intensity 8 hour componento (Fig. 1). Reseparation 5 days after

ir-radiation produced an arsenic fraction with a half-life of 40 hours while

the sole half-life in germanium was 11 days. These results indicate that

at the time of' the first separation the 12 hour Ge 77 was p:resent9 growing 71

into its 40 hour .As daughter after the separation. The resulting ha

lf-lives were observed as ~ 8 hours and 31 hours since the decay curve was

not resolvable into its 12 hour and 40 hour components. By the time of

the second separation the 12-hour activity had decaye'd out leaving only

the 11-day Ge 71 in the germanium fraction and the 40 hour a.cthri

t~j

in

the arsenice.

.A 40-hour activity is also reported2 for Ge69o This would have to

be_ produced by an ng 2n reaction in these experiments which is not

highly probable at these neutron ener~ieso In the present experiments

its presence would have been masked by the 40-hour .As 77 o .All that can

be said is that it was not produced in sufficient yield to be observed

when the second separation was run 5 days after the irradiation. How~

ever, if» as has previously been reported39 the 40-hour and ll~day

ger-11

manium activities were isomers of Ge 9 the former would be expected in

large enough amounts to be detectable 5 days after irradiation.

Con-sequently9 our evidence confirms the present assignmente Supporting

evidence was obtained by considering the sign of the particles as

determined by counting in a magnetic fieldo The 40-hour activity showed

(9)

..

cu

Q.

en

-

c

::;,

ISC-89

lopoo~---~

5,000

1,000

c3

500

8 Hours

100

0 5 10 15 20

Days After Bombardment

Fig. 1- Decay curve of Germanium.

50,000>,..---~

.

~

e

0.31 Mev Gamma Roy

KDo~--~~ooo~---,z~ooo~---..300~o---.~~oo~--,5uooo~~

Thickness of Aluminum in m0 m2

Fig. 2-Aluminum absorption curve of germanium three days

after bombardment.

30

(10)

assignment to As77 rather than Ge69 or Ge 71 which would be positron

emitterso The 11-day germaniumD on the other handD gave a higher

posi-tive than negative count showing that it decays to galliumo

By absorption measurement s it was

sho~

that a t?ray with a range of

1.0 g/om2 of aluminum. (Figo 2) energy 2ol Mev0 decayed out rapidly and

hence was mcst l:i.kely assooiated with the 12 hour Ge 77 o This agrees

with the previous value of 2o0 Mev4 for the Ge 77

~

rayo Also associated

wl th tr:.is decay was a gannna ray with a half~thickness in aluminum of

6o4 g/cm2 D corresponding to an energy of Oo3 Mevo The 11-day germanium

t?

ray had a range of 230 mg/cm2D energy Oo65 Mev. (Figo 3)

ARSENIC

77

The only activity observed in the arsenic fractions was As for

which the half-life was measured as 38

!

Oo5 hours0 (Fig. 4) compared

to the previously reported value of 40 hours4 Feather analysis of an

aluminum absorption curve (Fig. 5) gave a range of 246 mg/cm2 (Fig.

6),

corresponding to an energy of Oo68 Mev in agreement w.i th the value of

0.7 listed in the Trilinear Cbart5•

A portion of the arsenic sample was mounted for the thin-lens

mag-netic

~-ray

spe.otrometer and the

~-ray

spectrum was measured by E. No

Jensen of this laboratory6• The value so obtained was 0.679 Mev,

show-ing that the Feather method was reliable. TheE?-ray spectrum showed a

deviation from the straight-line Fermi plot at law energies, indicating

the possible presence of a component with an energy of Oo36 Mev and a

(11)

Q)

.... Q)

c.

ISC-89

10,000 ~---,

5,000

1,000 0

10.9 Days

Days After Bombardment

Fig. 3-Decay curve of germanium obtained from the second separation.

10,000 . - - - ,

.

~

·e

li

5,000

1,000

... 500

.

c "

0

<>

100

38 Hours

6 8 9 10 12 13 14 15

Days After Bombardment

Fig. 4 -Decay curve of arsenic obtained from the second separation.

25

[image:11.562.9.557.19.704.2]
(12)

300 E " c

·e

"

ct

-

0 .,E

~

E £

...

c 0 a: c:

0 200

Q.

Q. 0

ct

~.~r---,

100

.

'; 10

.£ E

.

~

1.0

0.1

0.1

Fig. 5-Aluminum absorption curve of arsenic.

0.2 0.3 0.4

mg.-( 2

'""•246

/Om~

0.68 Mev Beta Roy

0.5 0.6 0.7 0.8 0.9

Fraction of Range

Fig. 6 - Feather Analysis of Arsenic.

[image:12.568.11.554.10.691.2]
(13)

ISC-89 9

Jensen's current opinion that this is an artifact due to the reJativeJy

thick sample (0.8 mg/cm2 ) used in this case, and that a thin source would

probably not show thiso

Conversion lines from gamma rays were not seen in the results from

the beta spectrometer, but lead absorption curves (Figo 7) showed two

'0-rays of fairly low intensity~ Half-thickness values in lead were

85 mg/cm2 and 3o4 g/cm2 corresponding to energies of

0~05

and Oo42

~

.04

Mevo

GALLIUM

Three distinct gallium radioactivities were produced by the fast

neutron bombardment of germanium~ Decay periods of 15 hours, 53 hours and 14ol days are shown in Figure So A decay curve1followed over a period

of four half-lives indicates that the long-lived act:ivity has a half-life

I

of 14e5 days (Figure 9)o The 15-hour activity was identified with 14-hour

aa

72 ; the other two do not correspond to known gallium isotopeso

Several absorption curves in aluminum (Figo 101 and copper (Figo 11)

were taken at intervals during the course of the decay. The aluminum

curves were subjected to Feather analysiso It was observed that Oo29

and 0.71 Mev .{3-particles and a 34 Kev t"ray are associated with the

1405 day activity. The portion of the curves that is interpreted as

the Oo71 Mev

}?

might instead be due to a germanium X-ray, though its

intensity re la ti ve to the other components seems too high for this. The

(14)

.!!

E ~

..

.

"'

0

<)

5,000

1,000

500

100

..

;: "'

0

u

500r--- ---,

100

Roy

- 0.05 Mev Gamma Roy

10

0 3000 5000

Lead in mVcm2 Fig. 7 - Lead absorption curve of arsenic.

Dayt Afltr Bombordmtnl

[image:14.568.13.553.11.686.2]
(15)

JSC-89 11

IO,o o o r - - - ,

5,000

1,000

500

0

0 10 IS 20 2S 30 3S 40 4S so

Oaya Allor Bombardment

Fig. 9-Decay curve of gallium with some 38 hour arsenic present.

~r---~

so,ooo

10,000

s,ooo •

I

i.

J

1,000 0.71 Mev Beta Ray

soo

""0.04 Mev Gamma Ray IOC

0 100 200 300 400 soo

Thlckntu of Aluminum In m.Jc;;;.

[image:15.564.17.550.13.717.2]
(16)

!! ::J c:

e

~ •

...

• c ::J 0 ( ) 300~

----~---,

~

~---1.6-3~M--ev

__ G_a_m_m_a __

R_a_y---~---J

100 50 10 0 • ~ c:

e

i

...

..

c ::J 0

()

1-- - -0.034 Mev Gamma Ray

:l.

I I I I I I

1.0 eo 3.0 4.0 5.0 6.0

Thieknna of copptr -~cm2

Fig. 11-Copper absorption curve of gallium.

I O , O O O r - - - ,

5,000

1,000

~00

100

0 '5 10 15

Days After Bam bardment

Fig. 12-Decay curve of zinc.

20

[image:16.560.15.544.9.705.2]
(17)

ISC-89

1

3

f

-particles were found to be negatively charged by observation of the counts taken in a magnetic fieldo

Consideration of the P-ray energies involved indicates that the

14.5-day activity was either a nuclear isomer of Ga70 or unreported Ga 74 o The

53-hour activity may be a nuclear isom;r of Ga70 or Ga73 ~ or it may be

caused by Ga74o The assignment of any of the activities to Ga74 appears

to be somewhat questionable on the basis of following observations.

Sagan.e9 Miyamoto and Ikawa7 observed a 9-day gall:lum activity as a result

of bombarding germanium with deuterons and assigned it to aa74o Siegel

and Glendenin8 did not observe this 9-day gallium activity as a fission

product of uranium. McCown, Woodward, and Pool2 attempted to produce

Ga. 74 by the d.JrJ... reaction on germanium metal enriched to 70 per cent Ge 76 •

However, the only gallium activity observed was the 14-hour period of

Ga 72 o It can be seen by considering the isotopic abundances., the expected

stability of the nuclei using the Bohr-iVheeler type of calculation and

the fission yield distribution that half-lives of this length are less

probable for Ga. 76 than for Ga 74 o In the light of this conflicting evidence we are reluctant to make any definite assignments until further

work is carried outo

The possibility of the 53-hour .or l4o5-day activities being due to

the presence of radioactive impurities was shown to be highly unlikely

through consideration of the amounts of the impurities known to be presento

(18)

germanium yielded half-lives of 14 hours and 14 days (Figure 12).

Beta-particles were detected with energies of 0.91 Mev and 2ol Mev (Figure 13).

There were two a-rays of rv0.2 Mev and 0.,04 Mev (Figure 14)o The (-ray

energies are somewhat uncertain because of the low intensity of the

activity, however the beta-gamma ratio was 110, indicating that these

were

a

-rays and not bremsstrahlung ..

The Oo91 Mev

J3

a:nd the /!1 Oo2 Mev (were shown to decay with a 14

hour half-life9 corresponding to the isomeric transi t:ion (0.44 Mev ([)

and

)?

ray (10 Mev) reported9 for zn69 ..

The characteristics and assignment of the 14 day activity remain.

Chemical evidence is strong against its being due to an impurity, though

this remains a slight possibili tyo The 2.1 Mev

j3

and 40 kev

o

ray

belong 'Go the 14 day activity o The

.j3

rays were shown to be negatively

cp~rged by counting in a magnetic fieldo

Ann, ol reaction in germanium can produce zn69 , zn71 and zn73 ., Of

these zn69 is the 14 hour activity

discu~sed

above and zn71 is reported

8 10

to emit a

r

-ray of 2.1 Mev energy with a half-life of 2o2 minutes o

From this information it is seen that the most probable assignment of

the 14-day activity would be the unreported zn73 or a nuclear isomer

of 2.2 minute zn71o Of tha se two 1) g.eneral energy considerations could

make it appear unlikely that such a long half-life could be assigned to

Zn73 since the heaviest stable isotope is Zn70 • Also fission product

73

sttidies8 indicate that the half-life of Zn must be less than 2 minutes ..

Assignment of the 14 day activity to a nuclear iso~r of zn71 might be

(19)

~

"'

c

·

e

..

..

Q.

"'

5

0

(.)

ISC-89

1,500 . . . - - - ,

1,000

500

100

50

10

5.0

1.0

Gamma Roy

Roy

Roy

1000 1200 1400

Thickness of Aluminum in m.!Jcme

Fig. 13- Aluminum absorption curve of zinc.

5or---~

• 10

; c

·e

~50 Q. "'

-

c :0 0 0 1.0

i\o0.22 Mev Gamma Ray

)ff---0.04 Mu Gamma Ray

0 1.0 2.0 3.0

Thickneu of Copper in .Jc"m2

Fig. 14-Copper absorption curve of zinc.

[image:19.564.19.551.21.708.2]
(20)

energy of the 2.2 minute zn7lo The low abundance of zn7° (0.6%)

pos-sibly canbined w.ith a low cross s~ction for neutron capture by this

isotope would make a 14 day activity hardly observable in neutron

ir-radi.ateJ zinc compared to the fairly high activity of 250 day zn65

obtained from zn64 (abundance 49%, cross section Oo5 x

lo-

24 cm2 ).

Experime~ts are in progress to check the possibility of this isomerismo

SUMMARY

The following table summarizes the results obtained in the presen~

work.

Type of Energy of radiation inMev

)Juclide Halt'-life Radiation Particles ~-rays

Ge71 11 days

13 ..

DK Oo65 None

Ge77 12 hours

f3-

r

~ 2ol Oo31

As77 38 hours

p-r

Oo68 Oo42p Oo05

9

Ga70 or Ga74 14o5 days

P-

I

r

Oo29, Oo71 Oo034

Ga70 Ga73 g or Ga74 53 hours

p

- I I

r

lo9 lo63

(21)

ISC-89

17

lo Lo M. Dennis and Eo Bo Johnson, J. Amo Chemo Sooo, 45, 1380 (1923)0

-2o Do Ao McCown, Lo Lo Woodward and Mo Lo Pool Phys. ~o 74g 1311 (1948)o

3o Go To Seaborg, Jo Jo Livingood and G. Friedlander.~~ Phys. ~o, ~~

320 (1941).

4o Eo Po Steinberg and D. W. Englekemeier N.NoEoSo MPTS Div .. 4 Volo 9

Paper 54~ New York McGraw-Hill, 1950o

5o \Vo H Sullivan, Trilinear Chart~ Nuclear Species, New Yorkg Wiley, 1949o

6., Eo No Jansen, Priv., oomrmm.ication, 1950o

7o R .. Sagane.o Go Miyamoto, and M., Ikawa, Phys .. ~o9 59, 904 (1941).,

8. J., Mo Siegel and L. Eo Glendenin, NeNoEoS., MPTS.o Divo 4, Volo 9

Paper 53, New York, McGraw~Hill (1950)o

9o J., Wo KennedyD Go To Seaborg and Eo Segre,~~ Ph.l_!o ~o ~9 1095 (1939)e

10. Do Je Hughes~ J., Wallace~ Eo Goldfarb and

c.

Eggler, Reported in

G .. T .. Seaborg,

B.!!,o

~o Phys., !£,~~ 597 (1948).,

END OF-DOCUMENT

Figure

Fig. separation3-Decay curve of germanium obtained from the second .
Fig. 5-Aluminum absorption curve of arsenic.
Fig. 7-Lead absorption curve of arsenic.
Fig. 9-Decay curve of gallium with some 38 hour arsenic present.
+3

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