Gamma-ray emission from short-lived bromine and iodine isotopes

INORG.

NUCL.

CHEM.

LETTERS

Vol.

11,

pp.

331-339,

1975.

Pergamon

Press.

Printed

in

Great

Britain.

GAMMA-RAY EMISSION FROM SHORT-LIVED BROMINE AND IODINE ISOTOPES

K.-L. Kratz, W. Lauppe and G. Herrmann Institut fGr Kernchemie der Universitgt Mainz D-65 Mainz, Germany (Received 19 December 1974)

ABSTRACT Half-lives and main y-rays have been assigned to 88-92Br and 137-1411. The mass assignments are based on the genetic relationship of these nuclides to known decay products. Element assignments have been supported by coincidence measurements of x-rays and y-rays of unseparated fission products from 235U(nth,f ).

INTRODUCTION We have developed a rapid chemical separation procedure based upon the formation of volatile methyl-halides during and after the slowing down of fission fragments in methane (i). Counting of samples could be started within o.5 sec after the end of irradiation. This permitted the identification of halogen delayed neutron precursors with half-lives of only a few tenths of a second (2). This method was also used to study y-ray emission from shortlived halogen isotopes up to o.25-sec 92Br and o.45-sec l&ll! the results will be summarized in the following note.

331

332

Short-lived Bromine and Iodine Isotopes

Vol. 11, No. 5.

EXPERIMENTAL Irradiations were carried out in the Mainz Triga reactor using thermal n e u t r o n bursts of 30 msec FWHM and a flux o£ lo 15 n.cm -2. Details of the automatic procedure

are given elsewhere

gas-phase

separation

(I).

A first series of m e a s u r e m e n t s was carried out with a separation time of 25 sec to confirm the properties lived'

h a l o g e n isotopes!

series of m e a s u r e m e n t s

i.e. 86'87Br and 1361

(3-5).

'longerSeveral

were made with d e c r e a s i n g separation

times a c c o r d i n g to the h a l f - l i v e s nuclides.

o£ the

For the fastest

o£ the s h o r t e r - l i v e d halogen

separation the start of count time

was o.7 sec a£ter the end of irradiation. The bromine

and iodine samples

showed some contamination,

i n c r e a s i n g with d e c r e a s i n g separation times, by rare gas nuclides and their alkali to incomplete

daughter products.

These c o n t a m i n a t i o n s were due

removal of rare gas activities and due to the in-

growth o£ krypton and xenon as h a l o g e n daughter nuclides. definite

a s s i g n m e n t of h a l o g e n y-rays

it was n e c e s s a r y to measure

a clean rare gas fraction to know their y-rays. o£ uranyl

stearate were irradiated,

were absorbed, same conditions Oamma-ray

Therefore

samples

the emanating rare gases

and their y-ray spectra were m e a s u r e d under the as used for the h a l o g e n £ractions.

singles

spectra in the energy range of o.I to 2.o

MeV were recorded with a C e ( L i ) - d e t e c t o r

of 3o cm 3 active volume

and a r e s o l u t i o n o£ 2.6 keV FWHM at 1333 keV.

The spectra were

stored in lo24 channels of a 16 K m e m o r y and then, sequential

For a

spectra had been recorded,

after 16

t r a n s f e r r e d to a tape unit.

The shortest m e a s u r i n g times were 0.2 sec. To improve counting statistics

in each series the spectra of up to 25o identical

experiments were accumulated.

Vol. 11, No. 5.

Short-lived B r o m i n e and Iodine Isotopes

The y-ray spectra

in coincidence

with two Ge(Li)-detectors 5.9 keV for the x-rays y-rays.

The m e a s u r i n g

333

with x-rays were

with resolutions

recorded

of 2oo eV FWHM at

and 2.o keV FWHM at 1333 keV for the times were 2, 5 and lo sec.

RESULTS AND DISCUSSION The low energy part of a coincidence x-rays

with y-rays

the y-ray singles

from unseparated spectra

is shown in Fig.

spectrum

235U samples,

of the iodine

1. A comparison

of the Xe-K~ together with

and the rare gas fraction

of the singles

spectra

indicates

I I0~ -

~

~

--~,

/

: 2 . 0 - 4.0sec

} u

>, N

--

~

101]

--

200

400

600 ,~ Channel

FIG. Gamma-ray isotopes

singles

spectra

(c). On top

Xe-K~ x-rays.

800

1000

number

i

of short-lived

(a): y-ray spectrum

iodine

(b) and rare gas

in coincidence

with

334

Short-lived Bromine and Iodine Isotopes

that only a few relatively Most of the halogen butions,

lines

complicating spectrum

evidence,

as demonstrated

Energies

are superimposed

in coincidence

and relative

halogen y-rays

strong iodine y-rays

their identification.

the y-ray

V o l . 11, N o . 5.

by rare gas contriIn these

by Fig.

la. of some of the observed

are given in Table i. There

is good agreement

of our results with the data in the literature.

genetic

relationship

cases on y-x-ray

properties,

of the energies

(6,7).

decay schemes

available

(ii) half-life,

(iii) the

(iv) in some

and (v) for even-even nuclei

the systematics Reliable

Our assignments

to known rare gas daughters,

coincidences,

cases

with x-rays may give further

intensities

are based on (i) chemical

appear clearly.

of the first excited

on

states

could not be constructed

with the

data.

"~

~-"~

-~:Tsec Xe-141

CH3Br + CH31 _

_

I0 s

0,45sec I

~ 11]

I

I

,

,

,

10 4

.

103

1D2 15 m, Time after irradialion [see]

FIG.

2

Growth-and-decay

curves

isotopes

and 1411 obtained by following

91'92Br

of 91'92Kr and 141Xe from their mother

of the lo9.7 and 142.6 keV y-ray peaks and the lo7.o keV peak in the iodine

the intensities

in the bromine

fraction.

fraction,

Vol. 11, No. 5.

Short-lived Bromine and Iodine Isotopes

335

ITABLE 1 Energies and relative intensities of y-rays associated with the decay of short-lived bromine and iodine isotopes.

Ey (keV)

Rel. Int.

Ey (keV)

y-singles

(%)

775.8 ± o.2

loo

8o2.5 ± o.6

25

868.3 ± o.6

15

lo53.5 ± 1.4

lo

1578.4 ± 1.5

15

242.6 ± o.2

4o

242 ± 1

4ol.o ± o.3

9o

4oo ± 1

422.9 ± o.5

3o

423 ± 1

Literature

Nuclide

88Br

89Br

9°Br

± 2

4o

143o ! 2

15ol

± 2

loo

1499 ± 2

469.5 ± o.6

lo

468 ± 1

569.5 ± o.7

Io

7o7.4 ± o.6

loo

73o.9 ± o.8

2o

92Br

7o5 ± 2

2o

1364 ± 2

185.6 ± o.7 +)

3o

185 ± i

262.7 ± o.4 +)

loo

263 ± i

364.8 ± o.8 +)

4o

364 ± I

8o3.3 ± 1.2 +)

8o

8o5 ± 2

74o

± 2

± 2

+)

Ey (keV)

776.8 -+ o.3

1431

1361 91Br

yx-coinc.

(9)

869

± 5

(10)

7o6

± 4

(10)

336

Short-lived Bromine and Iodine Isotopes

Vol. 11, No. 5.

Table I (continued)

Ey (keV)

Rel.lnt.

Ey (keV)

Literature

Nuclide 1371

1381

139I

14°I

1411

y-singles

(%)

575.6 ± o.6

lo

6ol.9 ± o.4

2o

6ol

1219.1 ± o.4

loo

1217

13o2.3 ± o.6

3o

1873

lo

± 2

yx-coinc.

295.4 ± o.5

5

295 ± 1

37o.4 ± o.5

5

370 ± I

466.1 ± o.5

5

467 ± 1

482.7 ± o.3

15

483 ± 1

588.7 ± o.i

Ioo

258.7 ± o.3

3o

258 ! 1

527.7 ~ o.4

ioo

527 ± I

536.8 ~ o.7

5o

536 ± 1

571.1 ± o. 3

6o

571 ± 1

847.9 ± o.8

5o

847 ± 2

377.1 ± o.4

loo

378 ± 1

Y

(keV)

(4) ± 2

483.4

(4,9)

(6)

589.5 (6) 590.0 ± 0.3 (9) 585 ± 4 (lo)

457 -+ 1

457.7 -+ o.2

35

545.5 -+ o.6 +)

20

191.9 -+ o.5 +)

3o

191 ± 1

3o3.3 -+ o.7 +)

6o

304 -+ 1

387.3 ± o.5 +)

4o

386 -+ 1

578.8 ± o.4 +)

loo

578 -+ i

+) Tentative assignment

E

372

± 3

(lo)

376.8

(6)

457.9

(6)

Vol. 11, No. 5.

Short-lived Bromine and Iodine Isotopes

337

TABLE 2 Half-lives of short-lived halogen isotopes from y-ray spectroscopic measurements. Half-life (sec) This work

Nuclide

direct a)

Literature

indirect b)

88Br

16.2

-+ o.4

17.5 -+ i.I c) 15.88 + o.ll d)

89Br

4.5

+- o.4

4.55 -+ o.o9 d)

9°Br

1.63 -+ o.14

1.71 + o.ll

1.71 + o.14 e)

91Br

o.64 -+ o.o8

o.64 -+ o.o7

o.63 -+ o.o4 e,f)

92Br

o.3

o.25 + o.o7

o.26 -+ o.o4 e)

137I

24.2

+ o.15 +- 0.5

24.62 + o.o8 d)

1381

6.33 -+ o.o8

139I

2.42 -+ o.27

2.4

14°I

o.87 -+ o.o4

o.87 + o.13

o.89 -+ o.12 e) o.86 -+ 0.o4 f)

1411

0.45 -+ o. Io

0.48 -+ o.12

o.41 -+ 0.08 e) 0.42 -+ o.o8 f)

(1421)

6.9 + 2.4 c) 6.55 -+ o.ll d) + o.4

2.61 -+ o.ll d)

~ 0.2

a) Through decay of prominent halogen y-rays. b) Via the growth and decay of y-rays of rare gas daughters.

c) Through decay of prominent halogen y-rays (9). d) Value from neutron decay curves recommended in the data compilation Ref. (ll). e) From neutron decay curves (2). f) Via the growth of long-lived decay products (12).

338

Short-lived Bromine and Iodine Isotopes

Vol. 11, No. 5.

Our d~ta permit also the mass assignment of s h o r t - l i v e d h a l o g e n isotopes via the g r o w t h - a n d - d e c a y curves of strong y-rays of their rare gas daughters d e t e r m i n a t i o n of the half-lives the activities

(7,8). Fig. 2 shows the

of 91'92Br and of 1411 from

of 91'92Kr and 141Xe,

respectively.

For krypton

isotopes with h i g h e r mass numbers no ingrowth effects could be detected. evidence

In the xenon region there is still a slight

for a

mo.2

The half-lives

sec growth of 142Xe from 1421.

of the halogen nuclides o b t a i n e d from the

decay of strong y-rays and from the g r o w t h - a n d - d e c a y curves of their rare gas daughters

are listed in Table 2. The results

agree w i t h i n the error limits with other existing data. The data o b t a i n e d in the present work extend the knowledge about the decay properties beta stability line.

of n e u t r o n rich nuclei

Bromine and iodine isotopes decaying into

even-even krypton and xenon nuclei in the systematics a decrease

far from the

show the known smooth trends

of the energies of the first excited states:

in energies of the 2 + levels and an increase in the

E4+/E2 + ratios with increasing d i s p l a c e m e n t from the closed n e u t r o n shells N = 5o and N = 82.

ACKNOWLEDGEMENT We are indepted to the staff of the Mainz research reactor for numerous

irradiations,

of the experimental work, analysis.

The financial

to W. Eckhardt

for his help in some

and to H. Franz for his aid in data

support from the B u n d e s m i n i s t e r i u m

F o r s c h u n g und Technologie

is also gratefully acknowledged.

fGr

Vol. 11, No. 5.

Short-lived Bromine and Iodine Isotopes

339

REFERENCES

(I)

K.-L. Kratz and G. Herrmann, Radiochem. Radioanal.

Letters

~_2, 385 (1973). (2)

K.-L. Kratz and G. Herrmann, Nucl. Phys. A 229, 179 (1974).

(3)

A. Lundan, Z. Physik 242, lo7 (1971).

(4)

L.C. Carraz, J. Blachot, E. Monnand and A. Moussa, Nucl. Phys. A 158, 4o3 (197o).

(5)

E. Achterberg, F.C. Iglesias, A.E. Jech, J.A. Moragues, M.L. Perez, J.J. Scheurer and J.F. Suarez, Phys. Rev. C 5, 1587 (1973).

(6)

J.B. Wilhelmy, S.G. Thompson, R.C. Jared and E. Cheifetz, Report UCRL-19931 (197o).

(7)

K.-L. Kratz, Doctoral dissertation, Mainz 1972.

(8)

G. Erdtmann and W. Soyka, Tables of y-lines, Jgl-loo3-AC (1973).

(9) (lo)

A. Lundan and K. Anttila, Nucl. Instr. Meth. 79, 333 (197o) F. Horsch, Proc. Int. Conf. on the Properties of Nuclei far from the Region of Beta-stability,

CERN-Report 7o-3o,

p. 917 (197o).

(ll)

L. Tomlinson, Atomic Data and Nuclear Data Tables A 12, 179 (1973).

(12)

H. Ahrens, P. Patzelt and G. Herrmann, J. Inorg. Nucl. Chem.

submitted to