Electromagnetic properties of neutron-rich nuclei adjacent to the Z = 50 shell closure

Physics Le e s B 753 (2016) 86–90
Con en s lis s a ailable a ScienceDi ec
Physics Le e s B
www.else ie .com/loca e/physle b
Elec omagne ic p ope ies o neu on- ich nuclei adjacen o he
Z=50 shell closu e
M. Rejmund a, A. Na in a,∗, S. Biswas b, A. Lemasson a, M. Caamaño c, E. Clémen a,
O. Delaune a, F. Fa ge a, G. de F ance a, B. Jacquo a, P. Van Isacke a
aGANIL, CEA/DSM – CNRS/IN2P3, Bd Hen i Becque el, BP 55027, F-14076 Caen Cedex 5, F ance
bDNAP, Ta a Ins i u e o Fundamen al Resea ch, Mumbai 400005, India
cUSC, Uni e sidad de San iago de Compos ela, E-15706 San iago de Compos ela, Spain
a i c l e i n o a b s a c
A icle his o y:
Recei ed 14 Sep embe 2015
Recei ed in e ised o m 10 No embe 2015
Accep ed 24 No embe 2015
A ailable online 8 Decembe 2015
Edi o : V. Me ag
Keywo ds:
Iso opic iden ifica ion
La ge isospin and high angula momen um
Spin o bi pa ne s
In-Sb iso opes
M1/E2 ansi ions
Senio i y
Low-lying high-spin y as s a es in he exo ic odd–odd iso opes
124–128Sb (Z=51) and
118–128In (Z=49),
s udied o he fi s ime, show a s iking di e ence in hei obse ed γ- ay decay. Wi h a single alence
p o on pa icle/hole occupying he g7/2/g9/2spin-o bi pa ne s, dominan elec ic quad upole ansi ions
occu in Sb as opposed o magne ic dipole ansi ions in In. The obse ed p ope ies a e explained on
he basis o gene al p inciples o symme y and wi h la ge-scale shell-model calcula ions, and e eal
no el aspec s o he compe i ion be ween he neu on–p o on in e ac ion and he like-nucleon pai ing
in e ac ion.
©2015 The Au ho s. Published by Else ie B.V. This is an open access a icle unde he CC BY license
(h p://c ea i ecommons.o g/licenses/by/4.0/). Funded by SCOAP3.
Nuclea magne ic dipole (M1) momen s and ansi ions, ha ing
con ibu ions om bo h neu ons and p o ons, a e especially sui ed
o s udying spin and isospin cha ac e is ics o nuclei [1]. The mag-
ne ic momen μ(o g ac o , gJ=μ/μN, whe e Jis he nuclea
angula momen um) o a le el in an odd-mass nucleus is, in he
ex eme single-pa icle limi , gi en by he Schmid alue [2] ha
esul s om he pa allel o an i-pa allel coupling o he o bi al an-
gula momen um and he spin o he unpai ed nucleon. Obse ed
de ia ions om he Schmid alue ha e a ac ed a en ion since
he 1950s [3–5] and hei unde s anding emains an open p ob-
lem o his day [6–8]. The de ia ions a e a ibu ed mainly o co e
pola iza ion (coupling o λπ=1+pa icle-hole s a es in spin-o bi
pa ne shells) and o meson exchange cu en s (modifica ion o
he i ual-meson cloud a ound a nucleon, due o he p esence o
o he nucleons). M1 ansi ions be ween sho -li ed s a es eflec
he esemblance o he wa e unc ion o ini ial and final s a es,
p o ide in o ma ion ha is complemen a y o ha ob ained om
magne ic momen s, and ha e played a c i ical ole in un eiling he
exis ence o di e en modes o nuclea exci a ions [9–11]. Selec-
ion ules in M1 ansi ions can also be used o p obe symme ies
*Co esponding au ho .
E-mail add ess: na[email p o ec ed] (A. Na in).
and quan um numbe s. One such symme y is senio i y (essen-
ially he numbe o unpai ed nucleons), which is known o be
an app oxima e quan um numbe o iden ical nucleons in a sin-
gle shell [12,13] bu s ongly b oken in nuclei wi h neu ons and
p o ons in he alence shell.
The s ong spin-o bi coupling in he nucleus, a decisi e ing e-
dien o de e mining nuclea shell s uc u e, leads o a spli ing
o o bi s wi h j = +1/2 and j = −1/2. Among he a ious
gaps so c ea ed, he one a Z=50 is unique since i is he only
one wi h adjacen spin-o bi pa ne o bi s. The measu ed mag-
ne ic momen s o odd-mass Sb [14] and In [15] de ia e om hei
Schmid limi s (in an opposi e ashion), as can be unde s ood om
co e pola iza ion and meson exchange, and accoun ed o by a
eno maliza ion o he M1 ope a o wi h he inclusion o a enso
e m [6,7]. The e olu ion o he magne ic momen s wi h N[16]
is p esumably due o pa icle-co e coupling [14,17] bu why his
a ia ion occu s in Sb and no in In emains unclea .
In neu on- ich Sb and In iso opes, he alence p o on pa -
icle and hole occupy well-isola ed o bi s, g7/2o g9/2, espec-
i ely. These iso opes hus p o ide a unique possibili y o s udy
he ole o he indi idual magne ic p ope ies o a alence pa i-
cle/hole in spin-o bi pa ne o bi s in M1 ansi ions. Addi ionally,
he cha ac e iza ion o exci ed s a es o hese iso opes will allow
h p://dx.doi.o g/10.1016/j.physle b.2015.11.077
0370-2693/©2015 The Au ho s. Published by Else ie B.V. This is an open access a icle unde he CC BY license (h p://c ea i ecommons.o g/licenses/by/4.0/). Funded by
SCOAP3.
M. Rejmund e al. / Physics Le e s B 753 (2016) 86–90 87
Fig. 1. (Colo online.) A-and Z-iden ified Dopple -co ec ed γ- ay spec a o he
odd–odd
118–128In iso opes ( o ene gies g ea e han 600 keV he binning is dou-
bled). A smoo h backg ound is sub ac ed om hese spec a. The dashed line con-
nec s he mos popula ed ansi ion o each iso ope, co esponding o he decay o
he lowes popula ed exci ed s a e.
us o add ess he ques ions whe he he pa icle/hole na u e o
he p o on influences he s uc u al e olu ion wi h Nand o wha
ex en he p esence o one single alence p o on des oys he se-
nio i y symme y o he neu ons. Wi h he abo e mo i a ion, we
epo in his le e on elec omagne ic ansi ions, deduced om
p omp γspec oscopy o iso opically iden ified Sb and In iso opes
wi h N=73, 75, 77 p oduced in fission a an ene gy a ound he
Coulomb ba ie .
Odd-mass Sb and In iso opes ha e been in es iga ed by iso-
me decay and in-beam spec oscopy [18–21]. Odd–odd iso opes
ha e only been s udied by β-decay [22–28] and he spec oscopy
o hei high-spin s a es in he icini y o N80 is unknown. Ex-
ci ed s a es in nuclei a om s abili y ha e become accessible by
means o adioac i e-ion beams while hose a high angula mo-
men um ha e been s udied using he combina ion o la ge γ- ay
a ays wi h s able beams. Mo e ecen ly, he inc eased sensi i i y
o iso opic iden ifica ion o fission agmen s a ene gies a ound
he Coulomb ba ie , using a la ge-accep ance spec ome e cou-
pled wi h an efficien γ- ay de ec o a ay, ha e allowed he s udy
o nuclei a he ex emes o bo h spin and isospin [29,30].
The measu emen s we e made a GANIL using he magne ic
spec ome e VAMOS++ [31,32] in coincidence wi h he γ- ay
de ec o a ay EXOGAM [33]. F agmen s om usion–fission and
ans e -induced fission we e p oduced in collisions o
238U, a an
ene gy o 1.29 GeV, wi h a 10 μm- hick Be a ge . The ypical in-
ensi y o he beam was 109pa icles/s. The ime-o -fligh and he
posi ions o incoming ions, along wi h he known ion op ical p op-
e ies o VAMOS++, we e used o ob ain on an e en -by-e en basis
he magne ic igidi y Bρ, he eloci y ec o o he fission ag-
men VFF, and he mass-o e -cha ge A/q. The Ziden ifica ion o
he fission agmen was ob ained om he co ela ion o he en-
e gy loss and he o al ene gy. The ene gy o γ ays emi ed by he
nuclei was ans o med o he es ame by combining he mea-
su ed di ec ion o he γ- ay (using he segmen a ion o EXOGAM)
and VFF. Fu he de ails o he expe imen al me hod can be ound
in Re s. [29,30].
Fig. 2. A-and Z-iden ified Dopple -co ec ed γ- ay coincidence spec a o he
122,124,126In iso opes (a–c) and
126,128Sb iso opes (d–e).
The iso opically iden ified γ- ay spec a o he e en-mass
124–128Sb and
118–128In we e measu ed. Figu e 1 shows he spec a
o he mos exo ic iso ones measu ed in his wo k. All epo ed
γ- ay ansi ions a e obse ed o he fi s ime. The dashed line
indica es he e olu ion, as a unc ion o N, o he ene gy di e ence
be ween he wo lowes popula ed le els. I smoo hly dec eases
wi h inc easing N; a N=79 he end e e ses ( he 323 keV an-
si ion is he mos in ense) implying a change in s uc u e. In he
ollowing discussion we limi ou sel es o he mos neu on- ich
iso opes o Sb and In s udied he e. Figu e 2 shows he γ–γcoin-
cidence spec a o he nuclei whe e i was possible. The de i ed
pa ial le el schemes o N=73, 75, 77, ob ained using γ–γcoin-
cidences and ela i e in ensi ies, a e shown in Fig. 3.
The fission p ocess a o s he popula ion o y as s a es and he
p esen expe imen al se up is sensi i e only o s a es wi h li e imes
sho e han ∼2ns(as s a es wi h la ge li e imes decay a om
he Comp on supp essed a ay). The e o e, all J=2 ansi ions
can be assumed E2 as any o he mul ipola i y leads o le els ha
a e oo long-li ed o be de ec ed. Since c osso e ansi ions a e
obse ed, J=1is adop ed in he sequence o adjacen le els.
The co esponding ansi ions a e assumed o be M1, which a e
s ongly a o ed o e E2 o low-ene gy γ ays. I is unlikely ha
he J=1 sequences a e E1 ansi ions, hence he conce ned le -
els can be assigned he same pa i y. The wid h o he a ows in
Fig. 3 ep esen s he b anching a io, no malized o he same decay
p obabili y o each le el, wi h M1 (E2) ansi ions in ed (blue).
The a ios o educed ansi ion p obabili ies B(M1)/B(E2), ob-
ained om he measu ed b anching a ios, and he γ- ay ene gies
a e also shown. Wha s ands ou om Fig. 3 is: (i) he unexpec -
edly di e en decay pa e n, wi h a dominance o E2 ansi ions
in Sb and o M1 ansi ions in In; (ii) a s ong a ia ion (which we
conjec u e o be a s agge ing) wi h inc easing spin o B(M1)/B(E2)
a ios in he In iso opes; (iii) a smoo h inc ease o Sb and dec ease
o In, wi h neu on numbe , o he ene gy di e ence be ween he
wo lowes s a es. These obse a ions a e in e p e ed below.
The shell model in he ull ele an single-pa icle space leads
o ma ices o e y la ge dimension. Calcula ions a e he e o e ca -
ied ou in a es ic ed single-pa icle space consis ing o he neu-
88 M. Rejmund e al. / Physics Le e s B 753 (2016) 86–90
Fig. 3. (Colo online.) Pa ial le el schemes o he Sb and In iso opes buil on he
y as low-ene gy high-spin s a es p oposed in his wo k. Exci a ion ene gies (in keV)
a e ela i e o he 8−(Sb) o 9−(In) le el. T ansi ions in ed (blue) a e M1 (E2). The
wid h o he a ows ep esen s he b anching a io, no malized o he same decay
p obabili y o each le el. Also shown a e he deduced B(M1)/B(E2) a ios.
on (ν) d3/2, s1/2, h11/2o bi s, and he p o on (π) g9/2, p1/2,
g7/2o bi s nea he Fe mi su ace. The in e ac ion used is de-
i ed s a ing om he CD Bonn po en ial (jj45pn and jj55pn [34])
and calcula ions a e pe o med wi h he codes NATHAN [35] and
OXBASH [36]. The diagonal ma ix elemen s o he neu ons a e
adjus ed o accoun o missing co ela ions in he es ic ed model
space. E ec i e cha ges o eν=0.9 and eπ=1.8a e chosen so
as o ep oduce he measu ed B(E2) alues in he Sn and Te iso-
opes [37]. The o bi al and spin pa s o he M1 ope a o a e
aken as sugges ed by a mic oscopic calcula ion [7,14] and no en-
so e m is included (see below). Calcula ed low-spin le els a e
omi ed om he spec um and only he y as le els buil on he
lowes high-spin s a e (8−in Sb and 9−in In) a e shown in Fig. 4
( he fission p ocess a o s he popula ion o y as s a es). Fogel-
be g e al. [38,39] epo ed low-lying low-spin posi i e-pa i y (like
1+, 3+, 5+) s a es in
122,124,126In, no obse ed in he p esen wo k.
The p esence o he c osso e ansi ions connec ing he lowes
s a es obse ed in he p esen wo k allows o ule ou a change
o he pa i y o he le els in he sequence. The longe li e imes o
he M2 and highe mul ipola i y ansi ions, a e beyond he sensi-
i i y o he p esen expe imen (2ns). The ene gy di e ences
be ween he p oposed E(9−) −E(8−)(Sb) and E(10−) −E(9−)
(In) s a es (Fig. 3) and also hose o he highe -lying s a es, e ol e
smoo hly as a unc ion o Nin good ag eemen wi h he calcula-
ions (Fig. 4). The calcula ions o he In iso opes show ha he
B(M1) alues a e gene ally la ge, ∼1μ2
N, and he B(E2) alues
amoun o ∼200 e2 m4. In he Sb iso opes he B(M1) alues a e
smalle while B(E2) alues a e la ge han in In. The calcula ed
B(M1) alues also show a s agge ing as a unc ion o spin [ e-
la ed o obse a ion (ii)]. The good ag eemen o he calcula ions
wi h he obse a ions cons i u es he basis o he en a i e spin-
pa i y assignmen s and hus he M1 o E2 cha ac e o he ele an
Fig. 4. (Colo online.) Same as Fig. 3 o he ull shell-model calcula ion (see ex ).
The numbe s on he a ows a e he B(M1)o B(E2) alues, in uni s o μ2
Nand
e2 m4, espec i ely. To compa e wi h he B(M1)/B(E2) a ios quo ed in Fig. 3, he
B(M1) alue should be di ided by he B(E2) alue o he ansi ion s a ing om
he same le el.
ansi ions in Fig. 3. Fogelbe g e al. [39] measu ed he β-decay o
he high-spin s a es in
120,122,124,126,128In and en a i ely sugges ed
aJπo 8− o hese s a es. The calcula ions p edic he 8−s a e
o be he lowes in he ligh e In (A ≤120) iso opes, in
122In i is
close in ene gy o he 9−s a e whe eas in
124In i lies close o he
10−s a e and in
126In i is ∼500 keV abo e he 10−. I he low-
es s a e is assumed o be 8−, he co esponding sequence o he
exci ed s a es 8−, 9−, 10−would lead o a cascade o s ong M1
ansi ions, wi hou showing a s agge ing in B(M1)/B(E2) a ios
(as obse ed), since hese s a es belong o he same mul iple .
A deepe insigh in o he h ee ea u es seen in he da a (and
hei amifica ions) can be ob ained om a simplified e sion o
he abo e shell-model calcula ion whe e he obse ed low-ene gy,
nega i e-pa i y s a es a e conside ed o a ise om a p o on pa -
icle jπ=g7/2(Sb) o a p o on hole j−1
π=g−1
9/2(In) coupled o
nνneu ons in jν=h11/2. The obse ed dominance o E2 ansi-
ions in Sb and o M1 ansi ions in In [obse a ion (i)] can be
explained as ollows: i neu ons and p o ons a e confined o spe-
cific o bi s jνand jπ, he M1 ma ix elemen s a e p opo ional o
he di e ence o g ac o s, g(jν) −g(jπ). The calcula ed e ec i e
M1 ope a o [7] o a g( =4) p o on in his mass egion [14]
has g(πg7/2) =0.84 and g(πg9/2) =1.43. These compa e well
wi h he measu ed alues g(7/2+
1) ≈0.71–0.86 in odd-mass Sb
(depends on N) and g(9/2+
1) ≈1.22 in odd-mass In [16]. The co -
ec ions o he ee M1 ope a o (which do no include e ec s om
λπ= 1+co e pola iza ion [17] no wo-body e ms [40]) mainly
conce n he o bi al (+14%) and he spin pa s (−35%), as he en-
so e m con ibu es only 3% o he final esul . No e ec i e M1
ope a o is known o an h( =5) neu on in his mass egion. As-
suming he same spin quenching (−35%) o neu ons and p o ons,
one finds g(νh11/2) =−0.23, o be compa ed wi h he measu ed
alue g(11/2−
1) ≈−0.25 in odd-mass Sn [16]. The g ac o s hus
M. Rejmund e al. / Physics Le e s B 753 (2016) 86–90 89
de e mined lead o B(M1) alues ha a e ∼2 imes la ge in In
han in Sb, as obse ed in Fig. 4.
The esul s o he simplified shell model can be u he in e -
p e ed i a senio i y (o b oken-pai ) classifica ion is adop ed o
he neu ons. The in e ac ion be ween he neu ons has senio i y
as an app oxima e symme y, esul ing in a spec um ha , o an
odd numbe o neu ons in νh11/2, has a g ound s a e wi h senio -
i y υν=1 and angula momen um Jν=11/2(no b oken pai ),
and exci ed s a es wi h υν=3o 5 (one o wo b oken pai s).
I can be shown (based on fi s -o de pe u ba ion heo y) ha a
s a e wi h nνneu ons wi h senio i y υνin he o bi jνand nπ
p o ons wi h senio i y υπin he o bi jπis shi ed in ene gy by
he neu on–p o on (np) in e ac ion by an amoun Eνπ ,
Eνπ =nνnπ¯
Vjνjπ+υνυπ
1
2VαναπJ
jνjπ+VαναπJ
jνj−1
π
+ ν πυνυπ1
2VαναπJ
jνjπ−VαναπJ
jνj−1
π−¯
Vjνjπ,(1)
whe e ρ(ρ=νo π) is ela ed o he ac ional filling o he
o bi s, ρ=2(nρ−υρ)/(2jρ+1 −2υρ) −1. Th ee linea combina-
ions o he np in e ac ion ma ix elemen s VJ
jνjπoccu , namely
he monopole a e age
¯
Vjνjπ≡J[J]VJ
jνjπ/([jν][ jπ])and he
sums
VαναπJ
jνjπ≡[Jν][ Jπ]
J
[J]VJ
jνjπ
υ
νJ
ν
υ
πJ
π
×cυ
νJ
ν
υνυνJνcυ
πJ
π
υπυπJπ2⎡
⎣
jνjπJπJν
JJ
πJJ

ν
jνjπJπJν
⎤
⎦,
(2)
and
VαναπJ
jνj−1
π
≡−[Jν][ Jπ]
J
[J]VJ
jνjπ
υ
νJ
ν
υ
πJ
π
×cυ
νJ
ν
υνυνJνcυ
πJ
π
υπυπJπ2⎧
⎨
⎩
jνjπJπJν
JJ
πJJ

ν
jνjπJπJν
⎫
⎬
⎭
,
(3)
whe e [x] ≡2x +1, αρs ands o υρJρ, cυJ
nυJis a coefficien
o ac ional pa en age [12], cυJ
nυJ≡[jn−1(υJ)J|} jnυJ], and he
symbol in cu ly (squa e) b acke s is a 12 jcoefficien o he fi s
(second) kind [41]. Equa ions (2) and (3) a e he gene aliza ion o
nnucleons o he pa icle-hole heo em p o en in 1956 by Pandya
o n =2[42].
Equa ion (1), wi h np ma ix elemen s VJ
jνjπ aken om an em-
pi ical analysis [43] o , as is done he e, om he ull shell-model
calcula ion, is used o elucida e he e olu ion o s a es wi h neu-
on numbe . Fig. 5 shows he diagonal in e ac ion ene gies Eνπ
o he υν=1, Jν=11/2 (blue dashed line) and he υν=3,
Jν=9/2( ed dash-do ed line) neu on configu a ions o he
8−(Sb) o 9−(In) s a e, as a unc ion o he numbe o neu ons
nνin νh11/2. A c ossing o he υν=1 and υν=3 configu a ions
(indica ed by he a ows) occu s o bo h Sb and In. This is in con-
as o he e olu ion o he 9−(Sb) o 10−(In) s a e (no shown)
whe e he υν=1 configu a ion is always ound o be lowes in
ene gy o all nν.
Fig. 5 also shows he e olu ion wi h nνo he ela i e ene gy
o he wo same s a es a e diagonaliza ion (black solid line). The
ene gy di e ences E(9−) −E(8−)(Sb) and E(10−) −E(9−)(In)
can be seen o a y smoo hly o mos alues o nν, inc easing
Fig. 5. (Colo online.) E olu ion o he ela i e ene gy o wo high-spin s a es in
odd–odd Sb and In iso opes, as p edic ed by a simplified shell-model calcula ion.
The blue iangles (dashed line) and ed iangles (dash-do ed line) a e diagonal
in e ac ion ene gies Eνπ o he 8−(Sb) o 9−(In) s a e a ising om a υν=1,
Jν=11/2and a υν=3, Jν=9/2neu on configu a ion, espec i ely. The a ows
indica e he c ossing o configu a ions. The black do s (solid line) a e ob ained a e
diagonaliza ion. The pie cha s indica e he squa es o he ampli udes (a e mixing)
o he υν=1, 3, and 5 componen s in blue, ed, and whi e, espec i ely, o he
8−(Sb) o 9−(In) s a e. The g ay a ea co esponds o he occupancies o νh11/2
ele an o he iso opes s udied he e.
wi h nνin Sb and dec easing in In, as seen expe imen ally [ob-
se a ion (iii)] and in he ull shell-model calcula ion. Also shown
in Fig. 5 (as pie cha s) a e he squa es o he ampli udes o he
υν=1, 3, and 5 componen s o he wa e unc ion (a e mixing)
o he lowes 8−(Sb) o 9−(In) s a e. The e e sal o senio i-
ies is eflec ed in he pie cha s. Addi ionally, Fig. 5 e eals he
pa icle-hole symme y as a simila i y be ween he p ope ies o
an Sb iso ope wi h nνneu ons and hose o an In iso ope wi h
12 −nνneu ons. This gene ic beha io a ises due o he ‘Pandya’
s uc u e o Eq. (1) ( eminiscen o he co esponding exp ession
in e ms o quasi-pa icles [44]).
The su p ising and new ea u e e ealed by ou s udy is ha
he na u al senio i y o de ing is easily b oken. Fo he iso opes
o in e es he e, wi h 7 nν9 (occupancies o νh11/2as ob-
ained in he ull shell-model calcula ion), he senio i y in e sion
occu s in In, he υν=3 configu a ion being lowe in ene gy and
he dominan componen o he wa e unc ion. The ea u e o a-
o ing ene ge ically he s a e wi h one b oken pai o e ha wi h
no b oken pai s is due o he in e ac ion o a single p o on wi h he
neu ons. The cha ac e o he p o on (i.e., whe he i is a pa icle
o a hole) is o c ucial impo ance in his mechanism. The in e -
play o like-nucleon pai ing and neu on–p o on in e ac ion has
been he opic o p e ious s udies. Fo example, odd–e en s ag-
ge ing e ec s o binding ene gies [45] depend on his in e play
and, in pa icula , on he cha ac e (i.e. pa icle o hole) o he odd
nucleon [46]. The p esen in e p e a ion confi ms indeed he im-
po ance o his cha ac e in he b eaking o senio i y.
In summa y, he measu ed elec omagne ic decay o neu on-
ich odd–odd Sb and In iso opes is ound o be s ikingly di e en ,
and can be explained om he magne ic momen o a p o on in
spin-o bi pa ne o bi s. The wo k highligh s he impo an ole
90 M. Rejmund e al. / Physics Le e s B 753 (2016) 86–90
o a single p o on (pa icle o hole) in he mixing o he senio i y
quan um numbe , leading o he dominance o he highe -senio i y
configu a ion in he In iso opes. This esul is ound o be inde-
penden o he in e ac ion and demons a es he impo ance o
he neu on–p o on in e ac ion o e he like-nucleon pai ing in-
e ac ion in hese nuclei a om s abili y. This s udy calls o
sys ema ic measu emen s o li e imes and spec oscopic ac o s in
his egion o he nuclea cha . Apa om hei in insic in e -
es as ega ds he e olu ion o nuclea s uc u e a om s abili y,
hey could p o ide inpu s o a deepe unde s anding o he com-
ponen s o he e ec i e M1 ope a o .
Acknowledgemen s
We hank S. Bha acha yya and C. Schmi o help in a ious
aspec s o da a collec ion, analysis and many use ul discussions.
We acknowledge he impo an echnical con ibu ions o J. Goupil,
G. F emon , L. Ménage , J. Rope , C. Spi aels, and he GANIL accel-
e a o s a . We also hank B.A. B own o p o iding he jj55pna
and jj45pna in e ac ion files and V. Zele insky o e y use ul in-
sigh s o imp o ing he manusc ip . S.B. acknowledges financial
suppo o he s ay a GANIL h ough he LIA F ance-India ag ee-
men .
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