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Fission in he landscape o hea ies elemen s: Some ecen examples
Khuyagbaa a , J.; Yakushe , A.; Düllmann, Ch.E.; Acke mann, D.; Ande sson, L.-L.;
Block, M.; B and, H.; E en, J.; Fo sbe g, U.; Ha mann, W.; He zbe g, R.-D.; Heßbe ge ,
F.P.; Ho mann, J.; Hübne , A.; Jäge , E.; Jeppsson, J.; Kindle , B.; K a z, J.V.; K ie , J.;
Ku z, N.; Lommel, B.; Mai i, M.; Minami, S.; Rudolph, D.; Runke, J.; Sa mien o, L.G.;
Schädel, M.; Schaus en, B.; S eine , J.; De Heiden eich, T. To es; Uusi alo, Juha;
Wiehl, N.; Yakushe a, V.
Khuyagbaa a , J., Yakushe , A., Düllmann, Ch.E., Acke mann, D., Ande sson, L.-L.,
Block, M., B and, H., E en, J., Fo sbe g, U., Ha mann, W., He zbe g, R.-D.,
Heßbe ge , F.P., Ho mann, J., Hübne , A., Jäge , E., Jeppsson, J., Kindle , B., K a z,
J.V., K ie , J., . . . Yakushe a, V. (2016). Fission in he landscape o hea ies elemen s:
Some ecen examples. In D. Rudolph (Ed.), Nobel Symposium NS 160 - Chemis y
and Physics o Hea y and Supe hea y Elemen s (A icle 03003). EDP Sciences. EPJ
Web o Con e ences, 131. h ps://doi.o g/10.1051/epjcon /201613103003
2016
EPJ Web o Con e ences 131, 03003 (2016) DOI: 10.1051/epjcon /201613103003
Nobel Symposium NS160 – Chemis y and Physics o Hea y and Supe hea y Elemen s
Fission in he landscape o hea ies elemen s:
Some ecen examples
J. Khuyagbaa a 1,2,a ,A. Yakushe 2,Ch.E. Düllmann1,2,3,D. Acke mann2,b ,
L.-L. Ande sson1,M. Block1,2,3,H. B and2,J. E en1,3,c ,U. Fo sbe g4,W. Ha mann2,
R.-D. He zbe g5,F. P. Heßbe ge 1,2,J. Ho mann2,A. Hübne 2,E. Jäge 2,J. Jeppsson4,
B. Kindle 2,J.V. K a z3,J. K ie 2,N. Ku z2,B. Lommel2,M. Mai i6,d ,S. Minami2,
D. Rudolph4,J. Runke2,L.G. Sa mien o4,M. Schädel2,B. Schaus en2,J. S eine 2,
T. To es De Heiden eich2,J. Uusi alo7,N. Wiehl1,3, and V. Yakushe a2
1Helmhol z Ins i u e Mainz, 55099 Mainz, Ge many
2GSI Helmhol zzen um ü Schwe ionen o schung, 64291 Da ms ad , Ge many
3Johannes Gu enbe g-Uni e si ä Mainz, 55099 Mainz, Ge many
4Lund Uni e si y, 22100 Lund, Sweden
5Uni e si y o Li e pool, Li e pool L69 7ZE, UK
6Saha Ins i u e o Nuclea Physics, Kolka a 700064, India
7Uni e si y o Jy äskylä, 40351 Jy äskylä, Finland
Abs ac . The ission p ocess s ill emains a main ac o ha de e mines he
s abili y o he a omic nucleus o hea ies elemen s. Fission hal -li es a y
o e a wide ange, 10−19−1024 s. P esen expe imen al echniques o he
syn hesis o he supe hea y elemen s ha usually measu e -decay chains
a e sensi i e only in a limi ed ange o hal -li es, o en 10−5−103s. In
he pas yea s, measu emen echniques o e y sho -li ed and e y long-
li ed nuclei we e signi ican ly imp o ed a he gas- illed ecoil sepa a o
TASCA a GSI Da ms ad . Recen ly, se e al expe imen al s udies o ission-
ela ed phenomena ha e success ully been pe o med. In his pape , esul s
on 254−256R and 266L a e p esen ed and co esponding ac o s o e a ding
he ission p ocess a e discussed.
1. In oduc ion
The s abili y, i.e. he exis ence o an a omic nucleus ha consis s o Zp o ons and Nneu ons,
s ongly depends on he in e play be ween he a ac i e nuclea and epulsi e Coulomb
o ces. In hea y nuclei he la e o ce e en ually becomes dominan and spon aneous ission
(SF) limi s hei s abili y [1]. Some obse ables o he ission p ocess we e success ully
explained wi hin he liquid d op model, which also p edic ed ha nuclei wi h oo many
p o ons canno exis due o he absence o a (mac oscopic) ission ba ie (e.g. Z112
[2]). In he 1960’s he shell-s uc u e in luence on he mass o he a omic nucleus has
been in es iga ed and acco dingly he ission ba ie was ep esen ed as a supe posi ion o
aCo esponding au ho : [email p o ec ed]
bP esen add ess: GANIL, CEA/DSM-CNRS/IN2P3, Bd. Hen i Becque el, BP. 55027, 14076 Caen Cedex 5,
F ance
cP esen add ess: KVI-Cen e o Ad anced Radia ion Technology Uni e si y o G oningen, 9747 AA G oningen,
The Ne he lands
dP esen add ess: Indian Ins i u e o Technology Roo kee, Roo kee 247667, India
C
The Au ho s, published by EDP Sciences. This is an Open Access a icle dis ibu ed unde he e ms o he
C ea i e Commons A ibu ion License 4.0 (h p://c ea i ecommons.o g/licenses/by/4.0/).
EPJ Web o Con e ences 131, 03003 (2016) DOI: 10.1051/epjcon /201613103003
Nobel Symposium NS160 – Chemis y and Physics o Hea y and Supe hea y Elemen s
he liquid-d op and shell-co ec ion ene gy e ms [3,4]. Wi hin hese ea lie e sions o
he mac o-mic oscopic models he nex sphe ical magic numbe s Z=114 and N=184
ha e been p edic ed and nuclei a a ound hese numbe s a e in e ed o be su p isingly
s able agains spon aneous ission. A possible nex magic p o on numbe has se e al imes
al e na i ely been alloca ed o Z=120 o 126 wi hin mode n sel -consis en heo e ical
calcula ions [5,6].
To da e many supe hea y nuclei (SHN) wi h Zand Nup o 118 and 176, espec i ely,
ha e been syn hesized. The hea ies ones ha e been p oduced in 48Ca-induced usion
eac ions wi h ac inide a ge s and iden i ied by hei subsequen -decay chains, which
always ended wi h ission o ela i ely neu on- ich unknown iso opes o elemen s down o
Db [7].
One way o p obing Zand Aassignmen s o SHN is es ing he sys ema ics o
obse ables like -decay ene gies and -decay (T) and SF (TSF ) hal -li es. Especially TSF o
he ela i ely neu on- ich iso opes a he end o he Z=114−118 chains can be compa ed
wi h sys ema ics based on he well known neu on-de icien ones, whe e shell-s uc u e
e ec s a e well es ablished.
The shell s uc u e o he nucleus can s ongly a ec he s abili y agains ission, p ima ily
on i s mass su ace. Such an in luence can be s udied using he e en-e en nuclei as i
has been obse ed o N=152, whe e enhanced ission s abili ies we e ound compa ed
o neighbou ing iso opes o Fm (Z=100) and No (Z=102) elemen s. Single and mul i-
pa icle con igu a ions also hinde SF, and he s eng h o he hind ance depends s ongly on
he co esponding nuclea o bi als, e.g. quan um numbe s associa ed wi h in insic angula
momen um.
P esen expe imen al echniques o he de ec ion and iden i ica ion o SHN a e limi ed:
hey a e sensi i e o issioning nuclei wi h hal -li es oughly be ween ens o sup oa ew
hou s a mos . The iden i ica ion o nuclei wi h T1/2ou side hese limi s is challenging a
bes using s anda d expe imen al da a acquisi ion (DAQ) me hods. DAQ sys ems based on
as sampling ADCs ha e been in use o abou a decade o de ec ion o cha ged pa icles
[8]. Recen ly, such a me hod has success ully been implemen ed a he gas- illed ecoil
sepa a o TASCA and has been used o he i s ime in expe imen s dedica ed o syn heses
o SHN [9–11]. I s ad an ages o he de ec ion o pa icles ha e al eady been desc ibed
in Re . [12]. In he p esen pape i s bene i s o he de ec ion o SF-decaying nuclei will
be demons a ed wi h examples o bo h sho -li ed (254−256R [13]) and long-li ed (266L
[11]) iso opes. Each case co esponds o a pa icula e ec o he shell s uc u e on he
ission s abili y. Accumula ed da a and analyses p ocedu es o ission ac i i ies will also be
p esen ed: (i) Spon aneous ission o e en-e en 254,256R will demons a e he in luence o
he shell s uc u e on he nuclea mass. (ii) An in luence o he single-pa icle con igu a ion
on he ission s abili y will be shown wi h e en-odd 255R . (iii) Fission hind ances due o
mul i-pa icle con igu a ions will be demons a ed wi h e en-e en 254R (K-isome ic s a e)
and odd-odd 266L .
2. Expe imen al se up
Since 2009 he gas- illed ecoil sepa a o TASCA is a ailable o expe imen s aiming a SHN
and has success ully been used o he s udies o he elemen s le o ium (Fl, Z=114)
[14–16]), mosco ium (Mc, Z=115) [9], and Tennessine1(Ts, Z=117) [11]. TASCA
consis s o a de lec ing dipole and a ocusing quad upole double and can be ope a ed in
1He e we adop he sugges ed IUPAC names o elemen s 115 and 117.
2
EPJ Web o Con e ences 131, 03003 (2016) DOI: 10.1051/epjcon /201613103003
Nobel Symposium NS160 – Chemis y and Physics o Hea y and Supe hea y Elemen s
di e en ion-op ical modes [17], and wi h a ious ill gases [18], depending on expe imen al
equi emen s.
Nuclei conside ed in his wo k we e p oduced as e apo a ion esidues (ERs) o exci ed
compound nuclei o med in nuclea usion eac ions be ween 48Ca and 50Ti p ojec iles
(beam) and solid 204,206,208Pb [13] and 249Bk [11,19] a ge s. Pulsed beams (pulse leng h:
5 ms, epe i ion equency: 50 Hz) we e accele a ed by he UNI e sal Linea ACcele a o
(UNILAC) o ene gies a ound he Coulomb ba ie . Typical a ge hicknesses we e
0.5 mg/cm2. ERs lea ing he a ge wi h ela i ely high cha ge s a es wi h b oad dis ibu ions
en e he gas- illed olume o TASCA, whe e cha ge-s a e equilib a ing cha ge-exchange
p ocesses occu . A e su icien ly many collisions he cha ge-s a e dis ibu ion becomes
na ow a a ound an a e age one (o en q<10), be o e eaching he dipole magne ic ield.
Consequen ly, he ajec o y o he ERs h ough TASCA can be de ined by adjus ing he
dipole magne ic ield o hei magne ic igidi y [18,20]. Fo he p esen s udies TASCA
was illed wi h helium gas a 0.8 mba p essu e. A he ocal plane o TASCA, ERs we e
implan ed in o a double-sided silicon s ip de ec o (DSSSD) comp ising 144 e ical (X)
and 48 ho izon al (Y) s ips on he on and back sides, espec i ely.
TASCA was signi ican ly upg aded in 2011 by imp o ing i s pe o mance including
he assembling o a as DAQ sys em o he implan a ion de ec o s [21]. All p e-ampli ie
signals om he Y-s ips o he DSSSD we e digi ized by 60 MHz-sampling ADCs and
s o ed in 50 s-long aces. Signals om he X-s ips o we e p ocessed wi h s anda d analog
elec onics and peak-sensing ADCs wi h a dead- ime o ⩽35 s. These analog and digi al
b anches, which independen ly ini ialized da a s o age, allowed de e mining he o igin o
e en s in wo independen ways [11,12,21].
3. Expe imen al esul s
3.1 SF o 256R , 255R and 254R
The iso ope 256R was p oduced in he 50Ti(208Pb,2n) eac ion. A ypical ene gy spec um o
ission agmen s de ec ed in he DSSSD by he analog pa o he DAQ is shown in Fig. 1a.
These high-ene ge ic e en s we e in an i-coincidence wi h signals om he MWPC. Spa ial
and ime co ela ion analysis be ween hem and p eceding e apo a ion esidues (he ea e
no ed as ER-SF) allowed o de e mine he hal -li e o 256R [see Fig. 2a] acco ding o a
me hod desc ibed in Re . [22]. T aces o hese ission e en s we e s o ed as sa u a ed signals
in he digi al pa o he da a. The sa u a ion is due o he limi ed dynamic inpu ange o
he sampling ADCs. The sa u a ion ime can be used as a a iable o he de e mina ion o
he ene gy deposi ed in he DSSSD by he ission agmen s in he digi al da a, as shown in
Fig. 1b. The ime dis ibu ion o ission e en s om decay o e en-odd 255R p oduced ia
50Ti(206Pb,1n) is shown in Fig. 2b. Due o he long hal -li e, 1.9(4) s, all ission aces we e
de ec ed as single sa u a ed signals simila o 256R .
254R was p oduced in he 50Ti(206Pb,2n) eac ion. Only a ew e en s wi h sa u a ed single
signal, like he ones shown in Fig. 1a, we e de ec ed. They we e ound o be co ela ed wi h
ERs wi hin he sho ime as shown in Fig. 2c. The co ela ion ime dis ibu ion o hese e en s
was e mina ed a abou 50 s, because mos o he ission e en s om 254R we e eco ded
as a second signal in ER- aces. Thus, hese ission e en s we e los in he analog pa o he
da a as being an indi idual ission-like e en ! One o hem is exempli ied in Fig. 1d. Ene gies
o he i s signal in such aces we e co esponding o ER ene gies simila o ha obse ed
om he decay o 255,256R . A e ex ac ing such sho co ela ed ER-SF signals om he
ER- aces, he ull co ela ion ime dis ibu ion was econs uc ed; he co esponding hal -
li e o 254R was de e mined o TSF =20(3) s.
3
EPJ Web o Con e ences 131, 03003 (2016) DOI: 10.1051/epjcon /201613103003
Nobel Symposium NS160 – Chemis y and Physics o Hea y and Supe hea y Elemen s
0
5
10
15
50 100 150 200
0.5
1.0
1.5
0
1
2
0
1
2
0 500 1000 1500 2000 2500 3000
0
1
2
e)
d)
c)
b)
Sa u a ion ime (1000 ch)
ER-SF(256R )
analog
Coun
Ene gy (MeV)
a)
sa u a ion ime
2.9 µs
9.4 µs
Fission signal (256R )
Ampli ude (a.u.)
2.3 µs
Fission signal (254R )
ER
e−
e
−
ER
Time (chan / 17 ns)
ER
Figu e 1. (a) Ene gy spec um and (b) sa u a ion imes o aces e sus ene gies o ission e en s om
he decay o 256R measu ed in he analog pa o he da a. (c)–(e) Examples o di e en ypes o aces
con aining ission e en s: (c) single-signal ace co esponding o 256R . (d) Double-signal ace whe e
he implan a ion signal (no ed by ER) o 254R was ollowed by ission. (e) T iple-signal ace whe e
254mR was implan ed and a e 2.3 s he isome ic s a e de-exci ed o he g ound s a e which decays by
SF a e 9.4 s. The inse highligh s he egion o he elec on signal.
0
30
60
0
10
0
10
20
10
-7
10
-6
10
-5
10
-4
10
-3
10
-2
10
-1
10
0
10
1
0
2
4
d)
c)
b)
Τ
1/2
=6.7(4) ms
ER-CE-SF
ER-SF
ER-SF
ER-SF
a)
(
208
Pb,2n)
256
R
Τ1/2=1.9(4) s
(
206
Pb,1n)
255
R
Τ1/2=20(3) µs
(
206
Pb,2n)
254m
R
Τ1/2=4(1) µs
(
206
Pb,2n)
254
R
Time (s)
Coun s
Figu e 2. Co ela ion- ime dis ibu ion o ission e en s ela i e o p eceding ERs (a)–(c). The
dis ibu ion o single-signal ission aces which e mina ed a ≈50 s (ma ked by he do ed line)
is also shown in panel (c). (d) Time dis ibu ion o elec on-like signals ela i e o ERs co ela ed
wi h issions om 254R . Lines ep esen he calcula ed densi y dis ibu ion o he ission e en s on
a loga i hmic ime scale acco ding o Re . [22]. The cen e o g a i y o he dis ibu ion de e mines
he li e ime (=1.443 ·T1/2) o he issioning nucleus. Hal -li es o he co esponding iso opes wi h
unce ain ies (in he b acke ) and eac ions in which hey we e p oduced a e gi en. See ex o de ails.
Fu he mo e, in se e al aces o ER-like e en s a small signal was de ec ed in be ween
he ER and ission signals [23]. These signals wi h ampli udes no exceeding 500 keV we e
a ibu ed o o igina e om he egis a ion o elec ons. Time di e ences be ween he ER
and hese elec on-like signals a e shown in Fig. 1e. They ep esen an ac i i y wi h a hal -li e
o 4(1) s. The e o e, all obse ed e en s con aining ER-elec on-SF signals we e a ibu ed
o implan a ion o 254R in an isome ic s a e associa ed wi h he emission o con e sion
elec ons (CEs).
4

EPJ Web o Con e ences 131, 03003 (2016) DOI: 10.1051/epjcon /201613103003
Nobel Symposium NS160 – Chemis y and Physics o Hea y and Supe hea y Elemen s
3.2 Fission om 266L and -decay assignmen o 270Db
The nucleus 266L has no been p oduced di ec ly so a . In 2012 a TASCA, his iso ope was
assigned o be p oduced in -decay chains associa ed wi h 294117 [11]. I s sa e obse a ion
was possible hanks o se e al expe imen al condi ions, e.g., he use o a highly pixelized
DSSSD [15], as elec onics [11], he UNILAC pulsed beam, and well- uned TASCA [20]
ha allowed o assign a long-li ed decay o he mo he nucleus 270Db in bo h -decay
chains s emming om elemen 117.
As an example, ene gies o e en s measu ed in he pixel X=103 and Y=41 [11] wi hou
a coinciden signal om he MWPC a e shown in Fig. 3as a unc ion o ime coun ing om
he beginning o he expe imen . E en s occu ing in he DSSSD du ing beam o pe iods a e
ma ked by addi ional ho izon al lines. Wi hin he ene gy ange o 7–12 MeV whe e mos o
he known decays om hea y nuclei should occu , 55 beam-o e en s we e de ec ed. F om
he e en-by-e en analysis, 32 o hem we e iden i ied as o igina ing om known iso opes
a ound 208Pb p oduced in ans e eac ions (see Fig. 3).
Alpha decays in he egion “no heas ” o 208Pb occu wi h sho hal -li es. I he
-pa icle ene gy is abo e 8 MeV and i o igina es om nuclei wi h Z≈82−90 and
A≈210−230 hen he co esponding ERs can mos ly be ound in he da a wi hin 1 s [24].
The e o e, depending on he coun ing a e o he indi idual DSSSD pixel, he p edominan
amoun o beam-o e en s can be iden i ied.
Se e al e en s we e de ec ed wi hin a sho ime window (c . Fig. 3, clus e ). They we e
unambiguously a ibu ed o o igina e om elemen Z=117 based on he simila i y o
indings epo ed om he Dubna Gas-Filled Recoil Sepa a o (DGFRS) [25–27]. Only one
ission-like e en was obse ed 5.1 hou s a e he las  om he clus e -e en . In be ween,
ou -like e en s wi h ene gies o 6.82, 7.89, 11.53 and 6.29 MeV we e measu ed. Only he
7.89-MeV e en could no be assigned o any known iso ope. Fu he mo e, his was he only
one e en le wi hou an assignmen om in o al se en e en s de ec ed du ing he en i e
expe imen wi hin he ene gy ange o 7.7–8.2 MeV, whe e a possible decay o 270Db has
been discussed in Re . [27]. A simila si ua ion has occu ed in he second -decay chain,
whe e he ene gy o he co esponding e en was 7.90 MeV [11]. The e o e, hese e en s
we e a ibu ed o 270Db and he ission e en s ha e mina e he decay chains o he decay o
266L [11].
4. Discussion and summa y
The in luence o he shell s uc u e on he spon aneous ission o hea y nuclei is well isible
in sys ema ics o TSF , as shown in Fig. 4. The esul s on iso opes p esen ed in his wo k
[11,18] a e ma ked by solid symbols. Measu ed TSF o 254−256R we e in ag eemen wi h
li e a u e da a [24]. Maxima o TSF o Fm (Z=100) and No (Z=102) iso opes obse ed
a N=152 show he enhanced ission s abili y due o he shell closu e. Howe e , e en-e en
R (Z=104) iso opes do no anymo e show a well p onounced peak a N=152 compa ed
o ligh e elemen s. This migh be ela ed o a weakened in luence o he shell closu e on he
ission ba ie . These nuclei a e de o med, and hus he gaps be ween hose nuclea o bi als
esponsible o he shell closu e a e s ongly a ec ed by in e ac ions be ween he nucleons,
i.e. bo h numbe s o p o ons and neu ons. This is one o he dis inc e idences o di e ences
on he “magic” numbe s (Z=100, 108 and N=152, 162) occu ing in he de o med nuclei
om hose a , o example, Z=82 and N=126, whe e de o ma ion is absen .
In case o nuclei wi h an unpai ed p o on and/o neu on (odd-AR , L and Db), TSF a e
signi ican ly longe han in he neighbou ing e en-e en ones, showing he e ec o single and
5
EPJ Web o Con e ences 131, 03003 (2016) DOI: 10.1051/epjcon /201613103003
Nobel Symposium NS160 – Chemis y and Physics o Hea y and Supe hea y Elemen s
0 200 400 600
6
7
8
9
10
11
12
100
200
46 48 50 52
Ene gy (MeV)
Time (h)
7.89-MeV
Fission
Time (h)
Clus e
Figu e 3. Ene gy e sus ime plo o e en s de ec ed in pixel X=103 and Y=41 o he DSSSD whe e
one o he -decay chains associa ed wi h 294117 was obse ed [11]. The le panel shows he ull
ime pe iod o he expe imen . The igh panel shows a de ailed iew o he pe iod he chain was
obse ed. E en s wi hou a coinciden signal om he MWPC and occu ing du ing beam-o pe iods
a e ma ked by ho izon al and e ical lines, espec i ely. E en s wi h ene gies in he ange o 7–12 MeV
(an addi ional wo low-ene gy e en s in he igh panel), which we e iden i ied o o igina e om he
p oduc s o ans e eac ions, a e ma ked by addi ional solid squa es.
mul i-pa icle con igu a ions on he ission p ocess. We no e ha expe imen ally obse ed
SF b anches om odd-Aand/o odd-odd nuclei do no necessa ily always co espond o
he g ound-s a e decay. Though TSF o odd-AR , L and Db iso opes show a maximum a
N=153 associa ed wi h he in luence o bo h he N=152 shell closu e and single and/o
mul i-pa icle con igu a ions. An inc ease in TSF owa ds N=162 was obse ed in R -Hs,
and in he case o Db a peak-like end is obse ed a N=163 simila o he si ua ion
N=153, which indica es a shell closu e.
An in iguing inding is he assignmen o he long-li ed decay o 270Db. F om he
expe imen al da a analysis’ poin o iew, wo iden ical cases o 7.9 -MeV ’s we e clea ly
ound o be membe o he decay chains. Howe e , in Re . [28], he non-obse a ion
o analogous -b anching in he odd-Nneighbou 268Db (N=163) was poin ed ou ,
ques ioning he assignmen o decay in 270Db. Acco ding o Re . [28]-decay p ope ies o
268Db could be expec ed o be simila o hose o 270Db. Howe e , no decay was iden i ied
and assigned o 268Db in se e al expe imen s pe o med a DFGRS [28], TASCA [9] and
Be keley Gas- illed sepa a o (BGS) [29]. Howe e , we no e ha he DGFRS and BGS
expe imen s we e signi ican ly less sensi i e o measu ing long-li ed decay because o
he use o a DC beam whe e no (backg ound- ee) beam-o pe iods occu . The absence o
an -decay b anch in 268Db would mean ha i has a longe Tcompa ed o ≈1 hou o he
neighbou ing 270Db (N=165). Such cases a e well known o occu in odd-odd and e en-
odd nuclei loca ed abo e closed shells: o ins ance, To 256L (N=153) is abou eigh
imes longe han 258L (N=155). In cases o sphe ically shaped nuclei such Tdi e ences
be ween N=127 and 129 iso opes o odd-Zelemen s a y up o 6·105. Thus, i would no
be su p ising o expec a longe Tand di e en -decay ene gy o 268Db han 270Db. Fo he
u u e, mo e dedica ed expe imen s o sea ch o he long-li ed decay o 268Db and mo e
da a on 270Db need o be pe o med. Thei esul s will help o shed ligh on he shell s uc u e
a ound N=162. We also no e ha in he case o odd-odd nuclei whe e bo h decay and
SF a e hinde ed, o he adioac i e decay modes (decay and elec on cap u e) can become
p e e able. Recen ly, s a is ical analyses o he -decay chains a ibu ed o s a a Z=115
checking o he p esence o such decays, ha e been ca ied ou [31]. Thei esul s show ha
6
EPJ Web o Con e ences 131, 03003 (2016) DOI: 10.1051/epjcon /201613103003
Nobel Symposium NS160 – Chemis y and Physics o Hea y and Supe hea y Elemen s
136 140 144 148 152 156 160 164 168 172 176 180 184 188
10
-7
10
-4
10
-1
10
2
10
5
10
8
10
11
10
14
L L
Cm
C Fm
No
Sg
Hs
T
SF
(s)
Neu on numbe
Cn
Fl
3
1/21/2
10(R )T=(Db)T⋅
Db
R
152
184
162
Figu e 4. Pa ial SF hal -li es o e en-e en iso opes o he hea ies elemen s including odd-AR , L ,
and Db iso opes, as unc ion o neu on numbe . Solid symbols ma k expe imen al da a p o ided in his
pape , open symbols a e om li e a u e [24]. Theo e ically calcula ed TSF o e en-e en R iso opes a e
also gi en as dashed lines [30]. Dashed-do ed lines ep esen he same calcula ion bu mul iplied by
103, which simula es a hind ance ac o due o an unpai ed p o on and/o neu on. Loca ion o known
and p edic ed neu on shell closu es a e ma ked by e ical do ed lines.
di e en scena ios o he obse ed -decay chains can be p oposed, assuming ha one o
mo e o he chain-membe s unde wen elec on cap u e decay.
Appa en ly, he iden i ica ion o long-li ed nuclei a ound N=162 (expec ed also a
N=184) u ned ou o be a majo ask o u he SHN s udies. Sui able expe imen al
echniques ha e o be implemen ed.
Simila ly, e y sho -li ed issioning nuclei can also be s udied in he u u e as
demons a ed in he case o 254R and i s isome ic s a e. The la e obse a ion made h ough
elec on de ec ion wi hou eques ing a pa icula igge was possible hanks o a as DAQ,
whose u he ad an age o he solu ion o ission ela ed opics s ill needs o be explo ed.
Fo ins ance, he obse ed ER-CE-SF sequence o 254R indica es ha an isome ic s a e
is de-exci ing in o he g ound s a e ins ead o di ec ission. When such si ua ion occu s in
he s ongly spon aneously issioning nucleus hen he mos p obable o igin o he isome
is an exci ed s a e wi h high K-quan um numbe . K ep esen s he p ojec ion o he o al
nuclea spin along he symme y axis o he nucleus [32,33]. The same isome ic s a e in
254R has ecen ly been iden i ied and hal -li es a e in ag eemen [34]. A wo-quasi-neu on
con igu a ion ν7/2+[624] ⊗ν9/2−[734] o ming K=8 has been sugges ed o his 4-s
isome ic s a e in Re . [34]. An addi ional 247-s isome ic s a e has also been obse ed. In he
p esen expe imen a h eshold o he de ec ion o signals in he DSSSD we e no sensi i e
enough o measu emen s o elec ons, hus he 247-s-isome ic decays epo ed in Re . [34]
could no be obse ed.
K-hinde ed ission s abili y migh become an impo an issue o u he s udies o ul a
sho -li ed nuclei wi h ex eme numbe s o Zand N. Ve y neu on-de icien nuclei wi h TSF
much sho e han 1 s, which is app oxima ely he ligh - ime o ERs h ough sho in- ligh
sepa a o s o SHN, a e jus one example. Such an expe imen al scena io has been applied a
TASCA o he hi he o unknown 252R wi h a p edic ed TSF =0.6 s[30]; hese esul s will
be p esen ed elsewhe e [23].
We a e g a e ul o GSI’s ECR ion-sou ce and UNILAC s a , and he Expe imen al Elec onics
depa men o hei con inuous suppo o he expe imen s.
7
EPJ Web o Con e ences 131, 03003 (2016) DOI: 10.1051/epjcon /201613103003
Nobel Symposium NS160 – Chemis y and Physics o Hea y and Supe hea y Elemen s
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