Production cross section and decay study of 243Es and 249Md
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P oduc ion c oss sec ion and decay s udy o 243Es and 249Md
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B isele , R.; Theisen, Ch.; Vandeb ouck, M.; Ma chix, A.; Ai iau, M.; Au anen,
Kalle; Bad an, Hussam; Boilley, D.; Cal e ley, Tom; Cox, Daniel; Déche y, F.; Bisso,
F. De anchi; D oua , A.; Gall, B.; Goigoux, T.; G ahn, Tuomas; G eenlees, Paul;
Hauschild, K.; He zan, And ej; He zbe g, R. D.; Jakobsson, Ul ika; Julin, Rauno;
Juu inen, Saka i; Konki, Joonas; Leino, Ma i; Ligh oo , A.; Lopez-Ma ens, A.;
Mis y, A.; Nieminen, Päi i; Paka inen, Janne; Papadakis, Philippos; Pa anen,
Ja i; Peu a, Pauli; Rahkila, Panu; Rube , J.; Ruo salainen, Panu; Sandzelius,
Mikael; Sa én, Jan; Scholey, Ca he ine; So i, Juha; S olze, Sanna; Sulignano, B.;
Uusi alo, Juha; Wa d, A.; Zielinska, M.
B isele , R., Theisen, Ch., Vandeb ouck, M., Ma chix, A., Ai iau, M., Au anen, K., Bad an, H.,
Boilley, D., Cal e ley, T., Cox, D., Déche y, F., Bisso, F. D., D oua , A., Gall, B., Goigoux, T.,
G ahn, T., G eenlees, P., Hauschild, K., He zan, A., . . . Zielinska, M. (2019). P oduc ion c oss
sec ion and decay s udy o 243Es and 249Md. Physical Re iew C, 99(2), A icle 024614.
h ps://doi.o g/10.1103/phys e c.99.024614
2019
PHYSICAL REVIEW C 99, 024614 (2019)
P oduc ion c oss sec ion and decay s udy o 243Es and 249Md
R. B isele ,1Ch. Theisen,1,*M. Vandeb ouck,1A. Ma chix,1M. Ai iau,1K. Au anen,2,†H. Bad an,2D. Boilley,3,4
T. Cal e ley,2,5D. Cox,2,5,‡F. Déche y,1,6F. De anchi Bisso,2A. D oua ,1B. Gall,6T. Goigoux,1T. G ahn,2P. T. G eenlees,2
K. Hauschild,7A. He zan,2,§R. D. He zbe g,5U. Jakobsson,2,R. Julin,2S. Juu inen,2J. Konki,2,¶M. Leino,2A. Ligh oo ,2
A. Lopez-Ma ens,7A. Mis y,5,#P. Nieminen,2,** J. Paka inen,2P. Papadakis,2,5J. Pa anen,2P. Peu a,2P. Rahkila,2
J. Rube ,6P. Ruo salainen,2M. Sandzelius,2J. Sa en,2C. Scholey,2J. So i,2,†† S. S olze,2,†B. Sulignano,1J. Uusi alo,2
A. Wa d,5and M. Zieli´
nska1
1I u, CEA, Uni e si é Pa is-Saclay, F-91191 Gi -su -Y e e, F ance
2Depa men o Physics, Uni e si y o Jy askyla, P.O. Box 35, FI-40014 Jy askyla, Finland
3G and Accélé a eu Na ional d’Ions Lou ds (GANIL), CEA/DSM - CNRS/IN2P3, Bd Hen i Becque el, BP 55027,
F-14076 Caen Cedex 5, F ance
4No mandie Uni e si é, UNICAEN, Caen, F ance
5Depa men o Physics, Uni e si y o Li e pool, Oli e Lodge Labo a o y, Li e pool L69 7ZE, Uni ed Kingdom
6Ins i u Plu idisciplinai e Hube Cu ien, F-67037 S asbou g, F ance
7CSNSM, IN2P3-CNRS, F-91405 O say Campus, F ance
(Recei ed 28 Sep embe 2018; published 14 Feb ua y 2019)
In he s udy o he odd-Z,e en-Nnuclei 243Es and 249Md, pe o med a he Uni e si y o Jy äskylä, he
usion-e apo a ion eac ions 197Au(48Ca,2n)243Es and 203Tl(48Ca,2n)249Md ha e been used o he i s ime.
Fusion-e apo a ion esidues we e selec ed and de ec ed using a gas- illed sepa a o coupled wi h i s ocal-plane
spec ome e . Fo 243Es, he ecoil decay co ela ion analysis yielded a hal -li e o 24 ±3 s and a maximum
p oduc ion c oss sec ion o 37 ±10 nb. In he same way, a hal -li e o 26 ±1s,anα-b anching a io o 75 ±5%,
and a maximum p oduc ion c oss sec ion o 300 ±80 nb we e de e mined o 249Md. The decay p ope ies o
245Es, he daugh e o 249Md, we e also measu ed: an α-b anching a io o 54 ±7% and a hal -li e o 65 ±6s.
Expe imen al c oss sec ions we e compa ed o he esul s o calcula ions pe o med using he KEWPIE2 s a is ical
usion-e apo a ion code.
DOI: 10.1103/PhysRe C.99.024614
I. INTRODUCTION
De e mining he bounda ies o he nuclea cha , pa ic-
ula ly, in he egion o supe hea y nuclei (SHN), is one
*[email p o ec ed]
†P esen add ess: Physics Di ision, A gonne Na ional Labo a o y,
9700 Sou h Cass A enue, Lemon , Illinois 60439, USA.
‡P esen add ess: Uni e si y o Lund, Box 118, 221 00 Lund,
Sweden.
§P esen add ess: Ins i u e o Physics, Slo ak Academy o Sci-
ences, SK-84511 B a isla a, Slo akia.
P esen add ess: Depa men o Chemis y, Labo a o y o Radio-
chemis y, Uni e si y o Helsinki, P.O. Box 55, FI-00014 Finland.
¶P esen add ess: CERN, CH-1211 Gene a 23, Swi ze land.
#P esen add ess: GSI Helmhol zzen um ü Schwe ionen-
o schung GmbH, 64291 Da ms ad , Ge many.
**P esen add ess: Fo um Oyj, Powe Di ision, P.O. Box 100,
00048 Fo um, Finland.
††P esen add ess: Sodankylä Geophysical Obse a o y, Uni e si y
o Oulu, 90014 Oulu, Finland.
Published by he Ame ican Physical Socie y unde he e ms o he
C ea i e Commons A ibu ion 4.0 In e na ional license. Fu he
dis ibu ion o his wo k mus main ain a ibu ion o he au ho (s)
and he published a icle’s i le, jou nal ci a ion, and DOI.
o he key ques ions d i ing undamen al nuclea physics.
The SHN owe hei exis ence o shell e ec s as wi hou
hem he Coulomb epulsion would make he nuclei beyond
Z=104 uns able agains ission [1]. In his con ex , de ailed
spec oscopy o e y hea y nuclei (VHN) and SHN is o
pa amoun impo ance o p o ide in o ma ion on he nuclea
landscape close o he high-Alimi o he nuclea cha as well
as on he na u e o he p edic ed island o s abili y. The chal-
lenge o hese expe imen s is ela ed o low p oduc ion c oss
sec ions and, in odd-mass nuclei, o he complexi y o spec a
whe e a ious collec i e and single-pa icle exci a ions may
lie close in ene gy. On he o he hand, he s udies o odd-mass
nuclei a e ewa ded by he weal h o in o ma ion ega ding
single-pa icle s a es, exceeding wha can be ob ained o
e en-e en nuclei [2].
Rega ding he known exci ed s a es o single-pa icle o
collec i e na u e, li le da a is a ailable o Es (Z=99) and
Md (Z=101) iso opes [2,3]. Be o e in-beam spec oscopy
o hese odd-Znuclei can be a emp ed, easibili y s udies
a e a p e equisi e, in pa icula , measu emen s o p oduc ion
c oss sec ions. Such measu emen s also help o imp o e he
desc ip ion o he usion-e apo a ion eac ion mechanism,
p o iding new cons ain s o he models.
In his pape , he p oduc ion c oss sec ions o 243Es and
249Md popula ed di ec ly in he usion-e apo a ion eac ions
2469-9985/2019/99(2)/024614(9) 024614-1 Published by he Ame ican Physical Socie y
R. BRISELET e al. PHYSICAL REVIEW C 99, 024614 (2019)
197Au(48Ca,2n)243Es and 203Tl(48Ca,2n)249Md a e epo ed.
The a ge s and p ojec iles we e chosen as a comp omise
be ween he p edic ed p oduc ion c oss sec ions and he
ansmission in he sepa a o . In pa icula , e y asymme ic
eac ions using ac inide a ge s we e no conside ed as in such
cases: (i) The la ge angula dispe sion due o he low ecoil
eloci y and neu on emission esul s in a poo ansmission,
(ii) he low ecoil ene gy educes he de ec ion e iciency a
he ocal plane, bo h e ec s being no ully compensa ed by
enhanced c oss sec ions.
The p esen pape also allowed he hal -li es and decay
p ope ies o hese nuclei o be upda ed as well as hose
o 245Es, popula ed by he αdecay o 249Md. I should be
no ed ha α-decay b anching a ios and, o a lesse ex en ,
hal -li es a e needed o deduce p oduc ion c oss sec ions.
Finally, he measu ed p oduc ion c oss sec ions o 243Es and
249Md a e discussed in he con ex o he Z≃100 egion
and compa ed o he p edic ions o he KEWPIE2 s a is ical
usion-e apo a ion code [4].
II. EXPERIMENTAL SETUP
The expe imen s we e pe o med a he Accele a o Lab-
o a o y o he Uni e si y o Jy äskylä (JYFL). The usion-
e apo a ion esidues, including 243Es and 249Md, we e sepa-
a ed om he ission agmen s, he p ima y 48Ca beam and
he beam- and a ge -like eac ion p oduc s using he ecoil
ion anspo uni (RITU) gas- illed sepa a o [5,6], which
was ope a ed a a He p essu e o 0.4–0.6 mba s. The RITU
ansmission is es ima ed o be app oxima ely 30% o he
eac ions conside ed he e. The beam cu en was measu ed
a egula in e als using a Fa aday cup and moni o ed using
he de ec o s coun ing a e, hus, allowing he beam dose o be
deduced wi h an unce ain y o 20%.
A he ocal plane o RITU, he sepa a ed usion-
e apo a ion esidues we e i s de ec ed in a posi ion-
sensi i e mul iwi e p opo ional coun e (MWPC) and hen
implan ed in wo adjacen double-sided silicon s ip de-
ec o s (DSSDs), bo h de ec o s being pa o he γ e-
coil elec on α- agging (GREAT) spec ome e [7]. The
MWPC p o ided a ime-o - ligh (ToF) and ene gy loss
(E) measu emen , allowing: (i) selec ion o he usion-
e apo a ion esidues using a ToF-Eiden i ica ion ma-
ix and (ii) co ela ions wi h he DSSD, which enable
he ecoiling esidues (coincidence) o be disc imina ed
om he decay p oduc s (an icoincidence). Each DSSD is
300-μm hick and consis s o 60 ×40 s ips wi h a 1-mm
s ip pi ch. The Yside o he DSSD was calib a ed using an
ex e nal mixed 239Pu,241Am, and 244Cm-αsou ce. An ene gy
o se is applied o accoun o he ene gy loss o he αpa icle
in he de ec o en ance window (in he case o an ex e nal
sou ce) and o he daugh e nucleus ecoil (decay om
he de ec o a e implan a ion) so ha he esul ing ene gy
co esponds o he li e a u e alue o he nuclei s udied in he
p esen pape . The Xside was ampli ied wi h a highe gain
o measu e low-ene gy con e sion elec ons and calib a ed
using an ex e nal 133Ba sou ce. Signals om all de ec o s
we e p ocessed by a igge less acquisi ion sys em known
as he o al da a eadou [8]. The ecoil decay co ela ion
[keV]
DSSD
E
7000 8000 9000
Coun s/10 keV
0
5
10
15
co ela ionsαRecoil-
Es
243
FIG. 1. α-pa icle ene gy spec um o 243Es measu ed in he
DSSD esul ing om ecoil-αco ela ions using a maximum sea ch
ime o 268 s.
analysis was pe o med using he so wa e package GRAIN [9]:
A e he i s selec ion using he ToF-Eiden i ica ion ma-
ix, he usion-e apo a ion esidues ( ecoils) we e iden i ied
using he ene gy o he αpa icles egis e ed in he same
pixel o he DSSD subsequen o he implan a ion o a ecoil.
The SAGE a ay [10] su ounded he a ge o he p omp
γand con e sion-elec on de ec ion, howe e , da a om his
de ec o we e no used in he p esen wo k.
III. 243Es DECAY PROPERTIES AND PRODUCTION
CROSS SECTION
A. Decay and hal -li e measu emen
The 243Es iso ope was disco e ed in he 1970s by Es-
kola e al. using he 233U(15N,5n)243Es eac ion [11], and
la e e isi ed in he 1990 s by Ha sukawa e al. using he
233U(14N,4n)243Es eac ion [12]. A mo e ecen s udy, pe -
o med wi h he SHIP sepa a o a GSI by An alic e al. [13],
has shown ha 243Es decays o i s daugh e ia an αpa icle
wi h an ene gy o 7893 ±10 keV wi h a hal -li e o T1/2=
23 ±3 s and an α-decay b anching a io o 61 ±6%. An
α-pa icle ine-s uc u e was en a i ely obse ed wi h peaks
a 7745 ±20 and 7850 ±20 keV. In he wo k o An alic
e al. [13], 243Es was popula ed in he decay o he mo he
nucleus 247Md, whe eas in he p esen pape , i was di ec ly
p oduced in he 197Au(48Ca,2n)243Es eac ion, wi h a 21-pnA
48Ca beam a ∼210-MeV ene gy impinging on a 197Au a ge .
The 48Ca +197Au eac ion has al eady been s udied in he
1990s by Gäggele e al. [14], howe e , ew spec oscopic da a
we e a ailable a ha ime, p e en ing he disc imina ion o
usion-e apo a ion esidues om 2nand 3nchannels.
Figu e 1p esen s he α-pa icle ene gy spec um measu ed
in he DSSD esul ing om ecoil-αco ela ions wi h he
decay o 243Es clea ly isible.
The ime dis ibu ion (T)o heαdecay wi h espec
o he implan a ion, selec ing he 243Es α-decay ene gy, is
p esen ed in Fig. 2. In he inse , he ime dis ibu ion is d awn
as a unc ion o ln(T) using a maximum sea ch ime o
10 h. The peak a ln(T)=10.5 co esponds o he 243Es
decay, whe eas ha a ound ln(T)=16 is ela ed o andom
024614-2
PRODUCTION CROSS SECTION AND DECAY STUDY OF … PHYSICAL REVIEW C 99, 024614 (2019)
T [s]
0 50 100 150 200 250 300 350
Coun s/8 s
1
10
3 sEs) = 24
243
(
1/2
T
ln( T[ms])
0 2 4 6 8 101214161820
Coun s
0
2
4
6
8
10
12
14
Es
243
andom
FIG. 2. Time dis ibu ion o αdecays wi h espec o he 243Es
usion-e apo a ion esidue implan a ion. The inse shows he same
da a as a unc ion o ln(T) wi h Texp essed in milliseconds. I
should be no ed ha he ange is di e en o he wo spec a: 350 s
o he main panel and 135 h o he inse . The i using a wo-
componen decay cu e ( eal and andom) is shown wi h a solid line.
co ela ions occu ing a an a e age ime in e al o ≈5000 s.
The spec um in he main panel can be i ed using he unc ion
[15],
(T)=Ae−(λ+ )T+Be− T,(1)
whe e λis he decay cons an o he nucleus o in e es and
is he andom co ela ion a e. Simila ly, he spec um in he
inse can be i ed ollowing he me hod desc ibed in Re . [16].
As expec ed, bo h p ocedu es gi e he same esul , yielding
he hal -li e o T1/2=24 ±3 s, in ag eemen wi h he esul s
o he expe imen pe o med a SHIP [13].
The inse o Fig. 2demons a es ha he 243Es decay e en s
can be well sepa a ed om he backg ound in he de ined
ange o ln(T)<12.5, which co esponds o a ime window
o 268 s a e he ecoil implan a ion. This sea ch ime is used
in he nex sec ion in o de o de e mine he numbe o e en s
co esponding o he αdecay o 243Es.
The ecoil-α-αco ela ions we e used o sea ch o he
decay o 239Bk ollowing he 243Es decay. The nega i e ou -
come o his sea ch is again consis en wi h he esul s o he
measu emen a SHIP [13]. The decay p ope ies o nuclei
s udied in he p esen pape a e summa ized in Table I.
B. P oduc ion c oss sec ion
In o de o s udy he p oduc ion c oss sec ion o 243Es
using he usion-e apo a ion eac ion 197Au(48Ca,2n)243Es,
wo di e en beam ene gies we e used. The a ge used o
his measu emen was a 270 ±13-μgcm−2- hick 197Au sel -
suppo ing oil. The cyclo on deli e ed a 213.0±1.0-MeV
beam i s passing h ough he 100-μgcm−2ca bon window
o he SAGE elec on spec ome e . The i s pa o he s udy
was pe o med wi h a beam ene gy in he middle o he a ge
(MoT) es ima ed o be 210.0±1.0 MeV. Then, a ca bon
deg ade oil o 100 μgcm−2was placed ups eam o educe
he inciden ene gy (MoT) o 208.0±1.0 MeV. The spec um
p esen ed in Fig. 1co esponds o he o al s a is ics, namely,
wi h and wi hou he deg ade .
TABLE I. Summa y o decay p ope ies ob ained in he p esen
pape compa ed o he li e a u e alues.
Nucleus Hal -li e (s) α-decay b anching a io (%) Re e ence
243Es 24 ±3239Bk no obse ed This pape
23 ±361±6[13]
245Es 65 ±654±7 This pape
40 ±10 [17]
80+96
−28 80+20
−50 [18]
66 ±6[12]
55+12
−8.4[19]
249Md 26 ±175±5 This pape
25+14
−7>60 [18]
19+3
−2[20]
23.8+3.8
−2.9[19]
23 ±3[21]
75 [22]
The numbe o coun s a ibu ed o he 243Es αdecay was
ob ained using a maximum sea ch ime o 268 s. The con i-
bu ion om andom co ela ions was es ima ed by in eg a ing
he andom co ela ions componen [second e m in Eq. (1)
in he case λ ] using his ime window. A e sub ac ing
his backg ound, he numbe o αpa icles s emming om
243Es was de e mined o be 50 ±7(32±6) wi hou (wi h)
he ca bon deg ade oil. The unce ain ies we e e alua ed ol-
lowing he me hod desc ibed in Re . [23]. In he p esen wo k,
he s a is ics is la ge enough o conside s anda d no mal
dis ibu ions, he e o e, symme ic unce ain ies a e adop ed.
Du ing he acquisi ion ime wi hou and wi h he deg ade ,
he numbe o 48Ca nuclei ha impinged on he 197Au a -
ge was equal o (1.6±0.3) ×1016 and (1.2±0.2) ×1016,
espec i ely. Taking in o accoun he 197Au a ge hickness,
he α-decay b anching a io o 61 ±6% [13], he α-de ec ion
e iciency o 55%, and assuming a RITU ansmission o
30%, a p oduc ion c oss sec ion σ(243Es) =37 ±10 nb was
deduced o a beam ene gy o 210.0±1.0 MeV (wi hou
he deg ade ), and σ(243Es) =32 ±9 nb o a beam ene gy
o 208.0±1.0 MeV (wi h he deg ade ). Only s a is ical un-
ce ain ies co esponding o he beam dose, numbe o α
pa icles, and α-decay b anching a io a e gi en. The RITU
ansmission o 30% is ac ually a ansmission ×de ec ion
e iciency including he ansmission h ough he sepa a o ,
he ime-o - ligh , and he DSSD de ec ion e iciencies. The
esul s a e p esen ed in Table II.
TABLE II. P oduc ion c oss sec ions o 243Es using he usion-
e apo a ion eac ion 197Au(48Ca,2n)243Es measu ed o wo di e -
en 48Ca beam ene gies (Ebeam co esponds o he middle o a ge ).
Nαis he numbe o obse ed αdecays a e backg ound sub ac ion.
Ebeam (MeV) 48Ca dose Nασ(nb)
210.0±1.0(1.6±0.3) ×1016 50 ±737±10
208.0±1.0(1.2±0.2) ×1016 32 ±632±9
024614-3
R. BRISELET e al. PHYSICAL REVIEW C 99, 024614 (2019)
[keV]
DSSD
E
6500 7000 7500 8000 8500 9000
0
10
20
30 co ela ionsα-αRecoil-
Daugh e
(c)
10
20
30
40 co ela ionsα-αRecoil-
Mo he
(b)
20
40
60
80 co ela ionsαRecoil- (a)
Fm
249
Es
245
Md
249
Coun s/10 keV
FIG. 3. α-pa icle ene gy spec a o 249Md,249Fm and 245Es
esul ing om (a) ecoil-αand (b), (c) ecoil-α-αco ela ions using
a maximum sea ch ime o 10 min.
IV. 249Md DECAY PROPERTIES AND PRODUCTION
CROSS SECTION
The odd-Znucleus 249Md was popula ed using he usion-
e apo a ion eac ion 203Tl(48Ca,2n)249Md in h ee di e en
i adia ion campaigns. The i s campaign was ocused on
c oss-sec ion measu emen s a wo di e en bomba ding en-
e gies o 214.3±1.1 and 212.7±1.1 MeV. The esul s a e
epo ed in Sec. IV B. The wo subsequen campaigns aimed
p incipally a he in-beam and decay spec oscopy o 249Md,
esul s o which will be epo ed in a o hcoming pape . The
da a collec ed in he h ee campaigns we e used o de i e he
245Es and 249Md hal -li es and α-decay-b anching a ios as
p esen ed in he ollowing sec ion.
A. 249Md and 245Es decay and hal -li e measu emen
The α-pa icle ene gy spec a ob ained using ecoil-αand
ecoil-α-αco ela ions wi h he s a is ics o he h ee cam-
paigns summed oge he a e p esen ed in Fig. 3. A maximum
sea ch ime o 10 min a e he iden i ica ion o an implan ed
ecoiling nucleus was used. 249Md ea u es an elec on cap-
u e (EC)/β+-decay b anch eeding 249Fm. The αdecay o
he la e is obse ed using ecoil-αco ela ions since he
de ec ion sys em is insensi i e o he β+pa icle [see panel
(a)o Fig.3]. The 245Es αdecay obse ed using ecoil-α
co ela ions co esponds o he e en s when he αpa icle
emi ed om 249Md escapes om he DSSD wi hou being
de ec ed. The αdecay o 249Fm is mo e clea ly isible in
Fig. 4, which ep esen s he α-decay ime on a loga i hmic
scale as a unc ion o he α-pa icle ene gy. Using ecoil-α-α
co ela ions allows he mo he 249Md and daugh e 245Es α
decays o be isola ed as shown in he (b) and (c) panels
o Fig. 3. F om he li e a u e, he α-pa icle ene gies a e as
ollows: Eα(249Md) =8026 ±10 keV [21], and Eα(245Es) =
7730 ±1keV [12]. The sa elli e peaks in he αdecay o
249Md a 7956 and 8087 keV, sugges ed in Re . [21], a e also
en a i ely obse ed in he p esen pape .
[keV]
DSSD
E
7200 7400 7600 7800 8000 8200 8400
T[ms])Δln(
4
6
8
10
12
14 Fm
249 Es
245 Md
249
FIG. 4. α-decay ime dis ibu ion on a loga i hmic scale ( om
∼7ms o∼20 min) as a unc ion o he decay ene gy.
Figu e 5shows he ime dis ibu ion o he 249Md αdecay
wi h espec o he implan a ion ime. The dis ibu ion plo ed
as a unc ion o ln(T) o a maximum sea ch ime o 24 h
is shown in he inse . As shown in his plo , he andom
co ela ions a e negligible, he e o e, he ime dis ibu ion
displayed in he main panel can be i ed wi h a single ex-
ponen ial unc ion. A hal -li e o T1/2=26 ±1 s is ob ained
using a maximum sea ch ime o 300 s. This alue can be
compa ed wi h p e iously measu ed hal -li es. The 249Md
decay has been s udied a SHIP by Heßbe ge and co-wo ke s
ollowing he αdecay o 257Db(→253L →249Md) [18,20]
T [s]Δ
0 50 100 150 200 250 300
Coun s/s
1
10
T[ms])Δln(
0 2 4 6 8 10 12 14 16
Coun s
0
5
10
15
20
1 s±Md) = 26
249
(
1/2
T
FIG. 5. Time dis ibu ion o αdecays wi h espec o he 249Md
usion-e apo a ion esidue implan a ion. The inse shows he same
da a as a unc ion o ln(T) wi h Texp essed in milliseconds. I
should be no ed ha he ange is di e en o he wo spec a: 300 s
o he main panel and 18.2 h o he inse . The i using a one-
componen decay cu e is shown wi h a solid line.
024614-4
PRODUCTION CROSS SECTION AND DECAY STUDY OF … PHYSICAL REVIEW C 99, 024614 (2019)
T [s]Δ
0 100 200 300 400 500 600
Coun s/10 s
1
10
T[s])Δln(
0123456789
Coun s
0
2
4
6
8
6 s±Es) = 65
245
(
1/2
T
FIG. 6. Time dis ibu ion o he αdecay o 245Es wi h espec o
he 249Md αdecay. The inse shows he same da a as a unc ion o
ln(T) wi h Texp essed in seconds. I should be no ed ha he
ange is di e en o he wo spec a: 600 s o he main panel and
2.25 h o he inse . The i using a one-componen decay cu e is
shown wi h a solid line.
and he αdecay o 253L [21] and by Ga es e al. using
he Be keley gas- illed sepa a o ollowing he αdecay o
257Db [19]. Ou e ised hal -li e o 249Md ob ained ia di ec
p oduc ion and wi h highe s a is ics is compa ible wi h he
alues ob ained in hese wo ks: 25+14
−7s[18], 19+3
−2s[20],
23 ±3s[21], 23.8+3.8
−2.9s[19]; see also Table I.
Simila ly, Fig. 6p esen s he ime dis ibu ion o he
245Es αdecay wi h espec o ha o 249Md, he ime ep e-
sen ed in linea and as a unc ion o ln(T) scales. Again,
he backg ound is ound o be negligible. The dis ibu-
ion was hen i ed wi h a single componen . The hal -
li e T1/2(243Es) =65 ±6 s was ex ac ed, a alue compa -
ible wi h hose ob ained by Heßbe ge e al. ollowing
he αdecay o 257Db(→253L →249Md →245Es): 80+96
−28 s
[18], by Ha sukawa e al. a e di ec syn hesis using
he usion-e apo a ion eac ions 238U(14N,7n)245Es and
237Np(12C,4n)245Es: 66 ±6s[12], and by Ga es e al. ol-
lowing he αdecay o 257Db: 55+12
−8.4s[19]; see also Table I.
The α-decay-b anching a io o 249Md is de ined as he
a io o he α-decay b anch o 245Es, o he o al decay
s eng h, including he EC/β+b anch o 249Fm. The la e is
e alua ed using he numbe o e en s a ibu ed o he 249Fm α
decay om Figs. 3and 4, co ec ed o he 249Fm α-decay-
b anching a io. A co ec ion is also applied o ake in o ac-
coun he ac ion o 249Fm nuclei ha decay du ing he sea ch
ime o 600 s. The 249Fm hal -li e o 2.6±0.7 min is aken
om he e alua ed da a [24]. The 249Fm α-decay b anching
a io o 15.6±1.0% is aken om Heßbe ge e al. [25],
which is mo e ecen han he e alua ion o Re . [24].1The
esul ing α-decay-b anching a io deduced in he p esen
1I should be no ed ha , in Re . [25], he hal -li e o 249Fm has no
been emeasu ed. The alue adop ed in his e e ence is ac ually ha
o he e alua ion o Re . [24], i.e., 2.6±0.7 min. In he mos ecen
NUBASE2016 e alua ion [26], he α-decay-b anching a io o 249Fm
wo k is bα(249Md) =75 ±5%. The e alua ed alue o
bα(249Md) >60% [24] co esponds o he measu emen o
Heßbe ge e al., which has been ob ained in he s udy o he
257Db decay chain [18]. A mo e ecen alue o bα(249Md) =
75%, quo ed wi hou unce ain y in he Ph.D. hesis o S e-
iche [22], is in pe ec ag eemen wi h ou measu emen ; see
also Table I.
The α-decay-b anching a io o 245Es can be ex ac ed
in wo dis inc ways. The i s possibili y is o de i e i as
he a io o he numbe o e en s co esponding o 249Md
ob ained using ecoil-α-αand ecoil-αco ela ions, co ec ed
o he DSSD e iciency o a ull-ene gy measu emen α=
55% unde he condi ion ha he ecoil-α-αco ela ions a e
ob ained by ga ing on he ull-ene gy peaks only,
bα(245Es) =N ecoil-α-α(249Md)
N ecoil-α(249Md)
1
α
.(2)
The second op ion is o ob ain i as he a io o coun s co e-
sponding o 245Es and 249Md in he o al α-pa icle spec um.
Bo h me hods lead o he same alue o bα(245Es) =54 ±
7%. Fo compa ison, he p e iously epo ed alues we e
bα(245Es) =40 ±10% (Eskola [17]), bα(245Es) =80+20
−50%
(Heßbe ge e al. [18]). The decay p ope ies o 249Md and
245Es a e summa ized in Table I.
B. P oduc ion c oss sec ion
The usion-e apo a ion eac ion 203Tl(48Ca,2n)249Md was
s udied a wo di e en bomba ding ene gies. The cy-
clo on deli e ed a 218-MeV beam i s passing h ough he
100-μgcm−2ca bon window o he SAGE elec on spec om-
e e . The 203Tl a ge ha ing a hickness o 318 ±16 μgcm−2
was e apo a ed on a ca bon oil o 20 μgcm−2and co e ed
by a 10-μgcm−2ca bon p o ec ion laye . The esul ing ene gy
in he middle o he 203Tl a ge was es ima ed o be 214.3±
1.1 MeV. Using in addi ion an 80-μgcm−2ca bon deg ade
oil esul ed in an ene gy o 212.7±1.1MeVMoT.
The spec a we e ob ained using a sea ch ime o 207 s,
i.e., eigh 249Md hal -li es. Con a y o he 243Es case, he
backg ound was ound o be negligible.
The o al numbe o 48Ca pa icles ha impinged on
he a ge was (1.8±0.4) ×1015 [(1.5±0.3) ×1015] o he
measu emen wi hou (wi h) he ca bon deg ade oil. Using
a203Tl a ge hickness o 318 ±16 μgcm−2,anα-b anching
a io o 75 ±5%, a RITU ansmission ×de ec ion e iciency
o 30% and a ull-ene gy α-de ec ion e iciency o 55%, c oss
sec ions σ(249Md) o 300 ±80 and 70 ±40 nb a e deduced
o he inciden ene gies o 214.3 and 212.7 MeV, espec i ely.
Again, only s a is ical unce ain ies a e gi en. The esul s a e
summa ized in Table III.
V. DISCUSSION
In his sec ion, we discuss he new c oss-sec ion measu e-
men s o 243Es and 249Md. These esul s a e placed in he
is aken om Re . [24](33±9%), whe eas o he hal -li e only he
alue om Re . [27](96±6 s) is selec ed.
024614-5
R. BRISELET e al. PHYSICAL REVIEW C 99, 024614 (2019)
TABLE III. P oduc ion c oss sec ions o 249Md using he usion-
e apo a ion eac ion 203Tl(48Ca,2n)249Md measu ed o wo di e -
en 48Ca beam ene gies (Ebeam co esponds o he middle o he
a ge ).
Ebeam (MeV) 48Ca dose Nασ(nb)
214.3±1.1(1.8±0.4) ×1015 68 ±8 300 ±80
212.7±1.1(1.5±0.3) ×1015 12 ±470±40
con ex o expe imen al c oss sec ions o cold usion-
e apo a ion eac ions and he 2nchannel o Z≈100, p e-
sen ed in Fig. 7and compa ed o new eac ions dynamics
calcula ions using he s a is ical usion-e apo a ion code KEW-
PIE2[4].
A. 2nchannel usion-e apo a ion sys ema ics
I is gene ally acknowledged ha he usion-e apo a ion
eac ions can be desc ibed as h ee subsequen independen
p ocesses: cap u e, compound-nucleus o ma ion, and su -
i al o he esidual nucleus. The desc ip ion o he cap u e
s ep is a he well con olled in e ms o ba ie pene a ion
wi h no apid e olu ion as a unc ion o mass and cha ge
when using simila p ojec iles and a ge s. The o ma ion s ep
esul s in a sha p dec ease in he c oss sec ion o p ojec ile-
a ge combina ions wi h ZpZ 1600–1800, known as he
usion hind ance, which p e en s he o ma ion o a com-
pound nucleus by leading he dinuclea composi e owa ds he
quasi ission ou e. This e ec s a s o ac in he egion consid-
Z esidue
98 100 102 104 106 108
C oss sec ion [nb]
-3
10
-2
10
-1
10
1
10
2
10
3
10
Ca beam, his wo k
48
Ca beam
48
o he beam
250
252
253
254
249
251
244
246
250
243
244
238
240
241
255
256
257
259
260
261
264
FIG. 7. Sys ema ics o he usion-e apo a ion c oss sec ions in
he 2nchannel as a unc ion o Zo he esidual nucleus. The
illed ed squa es co espond o eac ions induced by a 48Ca beam,
whe eas he blue ci cles co espond o hose using o he beams. The
new 243Es and 249Md measu emen s a e deno ed by emp y squa e
symbols. The mass numbe Ao he esidual nucleus is gi en o he
igh o each symbol. Da a a e aken om Re s. [28](
238,240,241C ),
[29](
244C ), his pape (243Es,249Md), [30](
244,246Fm), [31](
250Fm),
[32](
251Md), [33](
250No), [34](
252,253No), [14](
254No,255L ), [35]
(256R ), [20](
257Db), [36](
259Sg), [21](
260Sg), [37](
261Bh), [38]
(264Hs).
e ed he e, and i can accoun o he exponen ial dec ease in
he c oss sec ions obse ed o la ge Z alues in Fig. 7. Con-
sequen ly, only he su i al s ep can accoun o he dec ease
in c oss sec ions below Z≈102. The global end displayed
by he c oss sec ions p esen ed in Fig. 7may be explained
by a combina ion o wo e ec s. Fi s , he ou old magic
cha ac e o he 48Ca +208Pb →256No∗ eac ion leads o a
low-Q alue and, he e o e, a highe su i al p obabili y in he
e apo a ion and de-exci a ion p ocesses. This enhancemen is
obse ed o 254No and neighbo ing esidual nuclei. Second,
he semimagici y a Z=100,N=152 leads o highe shell
co ec ions (highe ission ba ie ) and, he e o e, a highe
su i al p obabili y a ound 252Fm. No e ha , i he c oss
sec ions a e plo ed as a unc ion o he mass o neu on
numbe , hey also display a bell-shaped beha io .
B. C oss-sec ion calcula ions
In he ollowing, he usion-e apo a ion c oss sec ions
illus a ed wi h he new expe imen al esul s o 243Es and
249Md a e discussed in e ms o su i al om he compound
o he esidual nucleus wi h an emphasis on he e ec o he
ission ba ie . The p esen measu emen s a e pe o med in a
mass egion whe e he usion hind ance is no ye signi ican .
Consequen ly, he usion p ocess is modelled in he KEWPIE2
code by conside ing only he cap u e phase, which is com-
pu ed using a p oximi y po en ial and he Wen zel-K ame s-
B illouin (WKB) app oxima ion, see Re . [4] o de ails.
The KEWPIE2 code [4] ea s he compe i ion be ween
ligh -pa icle e apo a ion and ission, which occu s wi hin an
exci ed compound nucleus using he s a is ical o malisms
o Weisskop [41] and Boh -Wheele [42], espec i ely. The
en i e se o de aul pa ame e s used in he KEWPIE2 code is
p esen ed in Re . [4]. In he ollowing, we will only ocus on a
ew pa ame e s, which a e no well de ined ei he heo e ically
o expe imen ally in his mass egion [43]. These pa ame e s
a e he educed ic ion pa ame e β, he shell-damping en-
e gy Ed, and he shell co ec ions Esh. These pa ame e s a e
ela ed o he iscosi y o nuclea ma e , he s abili y o shell
co ec ions wi h empe a u e, and he ission-ba ie heigh ,
espec i ely, ollowing Eq. (3) o he la e :
B =BLDM −Esh,(3)
whe e B is he ission-ba ie heigh and BLDM is he liquid-
d op ission ba ie . The de aul alues used in he KEW-
PIE2 code a e β=2×1021 s−1,Ed=19 MeV, whe eas he
ini e- ange d ople model (FRDM) Esh shell co ec ions
a e aken om Re . [40]. I should be s essed ha hose
pa ame e s mainly a ec he ission p ocess ha is known o
be dominan o hea y and supe hea y nuclei. Indeed, a small
a ia ion o he ission pa ame e s, such as he s eng h o he
dissipa ion o he ission-ba ie heigh s, leads o a signi ican
modi ica ion o he su i al p obabili y and, consequen ly,
he ela ed obse ables, in pa icula , he p oduc ion c oss
sec ions.
Figu e 8p esen s he expe imen al esul s o he p o-
duc ion c oss sec ions o 243Es and 249Md (Tables II and
III) compa ed o he calcula ions pe o med wi h he KEW-
PIE2 code using he de aul pa ame e s. Fo 249Md, he
024614-6
PRODUCTION CROSS SECTION AND DECAY STUDY OF … PHYSICAL REVIEW C 99, 024614 (2019)
[MeV]
beam
E
195 200 205 210 215 220 225
[nb]σ
-3
10
-2
10
-1
10
1
10
2
10
3
10 Es Exp.
243
Es, KEWPIE2
244
Es, KEWPIE2
243
Es, KEWPIE2
242
(a)
[MeV]
beam
E
195 200 205 210 215 220 225
[nb]σ
-3
10
-2
10
-1
10
1
10
2
10
3
10 Md Exp.
249
Md, KEWPIE2
250
Md, KEWPIE2
249
Md, KEWPIE2
248
(b)
FIG. 8. Compa ison be ween he expe imen al p oduc ion c oss
sec ions o (a) 243Es ob ained in he p esen pape and he cal-
cula ions o he 1n,2n,and3nc oss sec ions pe o med wi h he
KEWPIE2 code using he de aul pa ame e s (mac oscopic pa de-
sc ibed by he Thomas-Fe mi pa ame iza ion as p oposed by Mye s-
´
Swi ˛a ecki [39] and he mic oscopic pa based on he FRDM shell
co ec ions [40]). (b) The same o 249Md.
calcula ion ep oduces he measu ed p oduc ion c oss sec ions
well, whe eas i unde es ima es hem by a ac o o 5 o
he 243Es case. The disc epancy o his la e case canno be
explained by a ailu e o he usion model. Indeed, o a beam
ene gy co esponding o he p esen measu emen (Ecm ≈
169 MeV), he usion model p o ides a usion c oss sec ion
σ us =55 mb in good ag eemen wi h he measu emen σ us =
42 mb o Re . [44]. Mo eo e , a discussion o he usion c oss
sec ion o he 48Ca +208Pb eac ion o which he WKB
app oxima ion p o ides a good desc ip ion wi hou usion
hind ance conside a ions can be ound in Re . [4]. In Fig. 9,
he ission-ba ie heigh s o he educed ic ion pa ame e s
ha e been inc eased in o de o ep oduce he measu emen s
o he 2ne apo a ion channel. Conce ning he ission-ba ie
heigh s, i is necessa y o add 500 keV o he absolu e alue
o he shell co ec ions [wi h he liquid-d op ission ba ie
kep unchanged, see Eq. (3)] o ob ain good ag eemen be-
ween he calcula ions and he da a. Fu he mo e, he educed
ic ion pa ame e has o be inc eased by a ac o o 3, i.e.,
o β=6×1021 s−1in o de o ob ain he same ag eemen .
[MeV]
beam
E
195 200 205 210 215 220 225
[nb]σ
-3
10
-2
10
-1
10
1
10
2
10
3
10 Es Exp.
243
+ 500 keV
sh
EΔEs,
243
+ 500 keV
sh
EΔEs,
242
3×βEs,
243
3×βEs,
242
FIG. 9. Compa ison be ween he expe imen al p oduc ion c oss
sec ions o 243Es ex ac ed in he p esen pape and he calcula ions
pe o med wi h he KEWPIE2 code conside ing ei he an adjus men
o +500 keV o he ba ie heigh s o an adjus men o he educed
ic ion pa ame e o β=6×1021 s−1.
I should be s essed ha hese adjus men s emain wi hin
he unce ain y in e als o hese pa ame e s as discussed in
Re s. [4,43]. Mo eo e , no heo e ical model can p esen ly
p edic he ission-ba ie heigh s wi h an accu acy be e han
0.5–1 MeV [45–47]. In he SHN egion, di e ences be ween
he models can be as la ge as 4 MeV [48]. Consequen ly, we
canno a ibu e he disc epancy obse ed o 243Es (Fig. 8)
o any speci ic pa ame e s used in he KEWPIE2 code no o
any inpu s om o he nuclea models, in pa icula , hose
ela ed o he ission p ocess. Hence, he measu ed p oduc ion
c oss sec ions o he 243Es and 249Md iso opes can be ully
explained wi hin he unce ain ies in nuclea models and phe-
nomenological pa ame iza ions implemen ed in he KEWPIE2
code.
A way o p o ide cons ain s on he pa ame e s used in he
KEWPIE2 code would be o use mo e p ecise measu emen s in
he VHN and SHN mass egions o a whole se o di e en
e apo a ion channels, including a la ge scan in exci a ion
ene gy o each o hem. Indeed, using ele an da a can help
o ix and/o elimina e he impac o a speci ic pa ame e . Such
an app oach based on he Bayesian in e ence is discussed in
Re s. [4,49].
VI. CONCLUSION
The odd-Z243Es and 249Md we e p oduced in
he 197Au(48Ca,2n)243Es and 203Tl(48Ca,2n)249Md
usion-e apo a ion eac ions, espec i ely. The hal -li e
o 243Es,249Md and i s daugh e 245Es we e measu ed, and
he esul s we e ound compa ible wi h hose ob ained in
p e ious measu emen s ollowing he αdecay o hea ie
nuclei. The p ecisions o he hal -li es o 249Md and 245Es
we e inc eased as well as hose o he α-decay-b anching
a ios o hose nuclei.
P oduc ion c oss sec ions o 243Es and 249Md ha e been
measu ed o he i s ime using 48Ca-induced eac ions and
compa ed o he calcula ions pe o med wi h he KEWPIE2
code [4].
024614-7
R. BRISELET e al. PHYSICAL REVIEW C 99, 024614 (2019)
ACKNOWLEDGMENTS
We acknowledge he accele a o s a a he Uni e si y o
Jy äskylä o deli e ing a high-quali y beam du ing he expe -
imen s. The Au a ge s we e kindly p o ided by GSI. Suppo
has been p o ided by he EU 7 h F amewo k P og amme
“In eg a ing Ac i i ies-T ansna ional Access” P ojec
No. 262010 (ENSAR) and by he Academy o Finland
unde he Finnish Cen e o Excellence P og amme (Nuclea
and Accele a o Based Physics P og amme a JYFL Con ac
No. 213503).
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