One-line γ ray spectroscopic investigation of the 180Hg(T 1/2 = 3 s) decay chain

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Submitted on 1 Jan 1977

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One-line γ ray spectroscopic investigation of the

180Hg(T 1/2 = 3 s) decay chain

J.P. Husson, C.F. Liang, C. Richard-Serre

To cite this version:

ONE-LINE

_03B3

RAY

SPECTROSCOPIC

INVESTIGATION

OF

THE

_{180Hg(T1/2 =}

3

_s)

DECAY CHAIN

J. P. HUSSON

Institut de

_Physique

_Nucléaire,

91406

_Orsay,

France C. F. LIANG

C.S.N.S.M.,

Bât. 104,

91406

_Orsay,

France and C. RICHARD-SERRE

IN2P3/CERN,

E.P.

_{Division, 1211,}

Geneva,

Switzerland

and

The ISOLDE Collaboration

CERN,

Geneva,

Switzerland

(Re~u

le 5 avril

1977,

revise le

_{6 juin}

1977,

accepte

le

_{7 juin 1977)}

Résumé. 2014

Avec le

_séparateur

ISOLDE 2 reconstruit, nous avons étudié en

_ligne

_{pour la}

_première

fois les

_produits

de

_{désintégration}

_{du 18080Hg.}

Les

_périodes

de

_{désintégration,}

les intensités des

prin-cipales

transitions y des

désintégrations

du 180Hg(T1/2

= 3,0 _± 0,3 s) _et de

18079Au(T1/2

= 8,1 _± 0,3 s)

et un schéma

_partiel

des états excités

de 18078Pt

sont

_présentés.

Abstract. - With the rebuilt ISOLDE 2

facility we have _investigated on-line the

_18080Hg

_decay

products.

The _{decay half-lives,} the

_energies

and intensities of the main 03B3 lines of both

180Hg(T1/2

= 3.0 _± 0.3 s) and

18079Au(T1/2

= 8.1 _± 0.3 s) ,

and a tentative decay scheme of

18078Pt

are

_given.

Classification

Physics Abstracts 21.10H - 23.20C

1. Introduction.

_{- Using}

the ISOLDE 2

_facility

one-line with the reconstructed 600

_MeV-proton

syn-chrocyclotron,

we have

_investigated

the A = 180

mercury

decay products

for the first time with our

new

_{tape transport system.}

The molten lead

_target

is

bombarded

_by

600 MeV

_protons,

_spallation

reactions

(p, 3pxn)

are induced and neutron deficient mer-cury nuclei are

_produced

and

mass-separated by

the ISOLDE 2

_separator.

The weakness of the

cross-section for the reaction

_{(p, 3p 26n)}

is such that an

increased

_intensity

of the

_proton

beam will be neces-sary for further studies.

Before this work the

_a-decay

_systematic

_study

of

_Hg

isotopes

and also the

_{delayed-proton}

emission cha-racteristics were studied

_by

another ISOLDE team

[1,

2].

In this letter we

_present

the half-live

measure-ments based on

_{multianalysis}

for the main y

transi-tions

_belonging

to

_{the 189Au}

_decay.

_Although

no y-y

coincidence

_experiments

could be

_performed,

we propose a

_{possible low-energy}

decay

scheme of

the

_ig8Pt

nucleus.

2.

_{Experimental procedure.}

- Due to the

y

back-ground

and to the low

_production

of this mass

(~10

at/s)

we

_performed

a

_~-y

coincidence

experi-ment. The

_separated

beam of

_180Hg

ions was

depo-sited on the

_tape

of the new

_moving

_tape

collector

system.

The _tape is then moved to the centre of a 4 7c

plastic

scintillator detector. A LASCO 50

cm3

_Ge(Li)

detector is

_positioned

in front of this

detector;

the

activity

of interest is enhanced

_by

_proper

_timing

selection of

collection,

delay

and

_counting

_time;

this

procedure

is

_repeated

as

_long

as is

required.

The _y energy spectrum in coincidence with the

_{plastic #}

counter

_pulses

is converted in an

Analog

to

_Digital

Converter

_{(Intertechnique}

CT

₁₀₃₎

on-line with a

Plurimat

_computer

_system. The

_experimental

set _up

arrangement is similar to that described

by

F. K.

Wohn et al.

_[3].

Two

_experiments

were done

_{simultaneously}

_during

a 48 hours

_period.

On the Plurimat

_cQmputer

_system

a

time-y

energy multianalysis (8

x At x

1024 channels)

was recorded

(At,

= 4

s,

At2

= 6

s).

On _a

_separate

L-246 JOURNAL DE _{PHYSIQUE -} LETTRES

multichannel

_analyser

a 4 k _{y-energy spectrum} was

constantly

accumulated

during

the

_{multianalysis}

expe-riment.

3. Results. - We have identified the main

y lines

belonging

to both _mercury and

_{gold decays}

(see Table

_I,

_Fig.

_1,

_2).

We have followed the

decay

of the main y lines in order to measure the half-lives and to confirm the attribution of the transitions to both

decays.

With a

least-squares fitting

code we obtain

18 OHg ’89Au

the half-life

Tl~~

= 3.0 _± 0.3 _s

for

_{’8 OAu ’88Au}

the half-life

T1~2

= 8.1 ± 0.3 s. A

_preliminary

result from the ISOLDE

_{Group [4]}

for the

_gold

_decay

_gave

T1~2 ~ 8.5 s .

The first value for the 2 + -~ 0~ transition _energy in

180 Au ~ 180pt

_{given by}

P.

_{Hornshcpj et}

al.

_[2]

was 150 ± 15

keV,

obtained from the

delayed-proton

emission

_study

of

_{181 Hg ;}

we find 152.3 _± 0.3 keV.

TABLE I

Energies

and relative intensities

_of

the main _y tr~ansitions observed

(1) Transition _belonging to both decays transitions in ( ) are weak.

FIG. 1. - Accumulated

y-ray spectra from Hg -+ Au -~ Pt _decays of mass 180 ₍₊ Hg -~ Au, · Au - _Pt, APt -+ Ir -+ _{Os). Spectrum} 1 is recorded with 8 s collection, 0 s _delay, and 8 x 4 s measurement (Hg -~ Au -~ Pt favoured). Spectrum 2 is recorded with 15 s _collection, 8 s

t(s) >

FIG. _2.-Example of the half-life determination in the A = _{180 chain.}

It is

_possible

that some of our _y lines attributions

are

_perturbed

_by

the

_decay

of the

_parallel

chain

_coming

from the a

_branching

of

Unfortunately

the _y transitions of these

decays

are

unknown

_[5].

We have considered that

_only

the _y lines whose relative

_intensity

with

_respect

to the

_strongest

_y line at 152.3 keV was conserved with two different

timing

measurements could be

_assigned

to the

180 Au

decay.

On the other hand no

_ambiguity

occurs for the y lines attributed to the

_{180Hg ~}

180Au

_decay.

4. Discussion. - Due

to the weakness of the

pro-duction we could not

_perform

_{any y-y} or

_e--y

coinci-dence

_experiments

to

_support

our level scheme

proposal.

By performing simple

sum

_{relationships}

calculations

with the transition

_energies

and

_comparing

with the excited levels

_systematics

of the heavier

_platinum

nuclei

_{[6, 7]}

_(see

_Fig.

₃₎

we _propose a

partial

scheme

(see

Fig.

4).

We believe we have identified the

2 i ,

4i , 2;, 3i, 2:

states.

FIG. 4. - Partial

decay scheme of _{~89Au -~}

_188Pt.

Present work

L-248 JOURNAL DE PHYSIQUE - LETTRES

These

_assumptions

are in _agreement with our

previous interpretation [6,

7]

of the behaviour of the neutron deficient

_{platinum isotopes :}

in

_fact,

the

prolate-oblate shape

transition occurs from

186Pt

to

188Pt and the three

nuclei i8o,i82.i84p~

show a rather similar level structure not _yet

_{perturbed, slowly}

varying

with little _energy differences. In

_particular

the

180pt

nucleus cannot be considered as

_truly

rota-tional : the ratio

is still far from the 0.7 rotational limit value as is the energy ratio

~4~/J52~ =

2.68

compared

to the 3.3

limit;

the three nuclei

180,182, 184pt

remain

slightly

deformed

(P

>

₀₎

but still transitional.

In

conclusion,

other

_experiments

are _necessary

to confirm this tentative

_{interpretation}

of the

180pt

nucleus

₍₀₁

excited state

location,

etc...)

but we

believe that this

_nucleus,

far from

_{the P}

_stability

line,

is

_{slightly prolate,}

and below 1.2

_MeV,

shows similar

_properties

to those of

182,184 Pt

nuclei.

The authors are indebted to G.

_Walter,

R. Huck and A.

_Knipper

for

_providing

the

_plastic

scintillator

_set-up

which made the

_experiment

_possible.

References

[1] HANSEN, P. G., NIELSEN, H. L., WILSKY, K., ALPSTEN, M.,

FINGER, M., LINDAHL, A., NAUMANN, R. A. and NIELSEN,

O. B., Nucl. _Phys. A 148 ₍₁₉₇₀₎ 249.

[2] HORNSHØJ, P., WILSKY, K., HANSEN, P. G., JONSON, B. and

NIELSEN, O. B., Nucl. Phys. A 187 (1972) 599 ;

JONSON, B., Ph. D. Thesis (1972) (unpublished).

[3] WOHN, F. K., GLASCOCK, M. D., TALBERT Jr., W. L., HSUE,

S. T. and HANSON, R. J., Phys. Rev. C 13 (1976) 2492.

[4] WESTGAARD, L., CERN EP Internal _Report 76-04 Production and Study of short-lived radioactive nuclei.

[5] Nuclear data sheets 1976.

[6] FINGER, M., FOUCHER, R., HUSSON, J. P., JASTRZEBSKI, J.,

JOHNSON, A., ASTNER, G., ERDAL, B. R., KJELBERG, A., PATZELT, P., HOGLUND, A., MALMSKOG, S. G. and HENCK,

R., Nucl. _Phys. A 188 ₍₁₉₇₂₎ 369.

[7] HUSSON, J. _P., FOUCHER, R., KNIPPER, A., KLOTZ, G., WALTER, G., LIANG, C. F. et RICHARD-SERRE, C., Proceedings of the 3rd International conference on nuclei far from 03B2