Physics Letters B 764 (2017) 265–270
Contents lists available at ScienceDirect
Physics Letters B
www.elsevier.com/locate/physletb
Towards saturation of the electron-capture delayed fission probability:
The new isotopes
240
Es and
236
Bk
J. Konki
a
, J. Khuyagbaatar
b,c,∗
, J. Uusitalo
a
, P.T. Greenlees
a
, K. Auranen
a,1
, H. Badran
a
,
M. Block
b,c,d
, R. Briselet
e
, D.M. Cox
f,2
, M. Dasgupta
g
, A. Di Nitto
c,d
, Ch.E. Düllmann
b,c,d
,
T. Grahn
a
, K. Hauschild
h
, A. Herzán
a,3
, R.-D. Herzberg
f
, F.P. Heßberger
c
, D.J. Hinde
g
,
R. Julin
a
, S. Juutinen
a
, E. Jäger
c
, B. Kindler
c
, J. Krier
c
, M. Leino
a
, B. Lommel
c
,
A. Lopez-Martens
h
, D.H. Luong
g
, M. Mallaburn
i
, K. Nishio
j
, J. Pakarinen
a
, P. Papadakis
a
,
J. Partanen
a
, P. Peura
a,4
, P. Rahkila
a
, K. Rezynkina
h
, P. Ruotsalainen
a
, M. Sandzelius
a
,
J. Sarén
a
, C. Scholey
a
, J. Sorri
a
, S. Stolze
a
, B. Sulignano
e
, Ch. Theisen
e
, A. Ward
f
,
A. Yakushev
b,c
, V. Yakusheva
b,c
a
University of Jyvaskyla, Department of Physics, P.O. Box 35, FI-40014 Jyvaskyla, Finland
b
Helmholtz Institute Mainz, 55099 Mainz, Germany
c
GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt, Germany
d
Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany
e
IRFU, CEA, Université Paris-Saclay, 91191 Gif-sur-Yvette, France
f
Department of Physics, Oliver Lodge Laboratory, University of Liverpool, Liverpool L69 7ZE, UK
g
Research School of Physics and Engineering, Australian National University, Canberra, ACT 2601, Australia
h
CSNSM, Université Paris Sud and CNRS-IN2P3, F-91405 Orsay Campus, France
i
School of Physics and Astronomy, The University of Manchester, Manchester M13 9PL, UK
j
Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
a r t i c l e i n f o a b s t r a c t
Article history:
Received
4 October 2016
Received
in revised form 9 November 2016
Accepted
21 November 2016
Available
online 24 November 2016
Editor:
V. Metag
Keywords:
Isotopes
with mass 236–240
240
Es
236
Bk
α decay
Electron-capture
delayed fission
Fusion–evaporation
reactions
The new neutron-deficient nuclei
240
Es and
236
Bk were synthesised at the gas-filled recoil separator
RITU. They were identified by their radioactive decay chains starting from
240
Es produced in the fusion–
evaporation
reaction
209
Bi(
34
S,3n)
240
Es. Half-lives of 6(2) sand 22
+13
−6
swere obtained for
240
Es and
236
Bk, respectively. Two groups of α particles with energies E
α
= 8.19(3) MeV and 8.09(3) MeV were
unambiguously assigned to
240
Es. Electron-capture delayed fission branches with probabilities of 0.16(6)
and 0.04(2) were measured for
240
Es and
236
Bk, respectively. These new data show a continuation of the
exponential increase of ECDF probabilities in more neutron-deficient isotopes.
© 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license
(http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP
3
.
*
Corresponding author at: GSI Helmholtzzentrum für Schwerionenforschung
GmbH, 64291 Darmstadt, Germany.
E-mail
address: J.Khuyagbaatar@gsi.de (J. Khuyagbaatar).
1
Present address: Physics Division, Argonne National Laboratory, Argonne, IL
60439,
USA.
2
Present address: University of Jyvaskyla, Department of Physics, P.O. Box 35,
FI-40014 Jyvaskyla, Finland.
3
Present address: Department of Physics, Oliver Lodge Laboratory, University of
Liverpool, Liverpool L69 7ZE, UK.
4
Present address: Helsinki Institute of Physics, FI-00014, Helsinki, Finland.
1. Introduction
One of the key challenges in understanding the creation and
isotopic distribution of elements in nature is knowledge of the sta-
bility
of the atomic nucleus. A nucleus comprised of Z protons and
N neutrons is a complicated quantum bound system that possibly
breaks up as a result of the interplay of the different fundamen-
tal
forces in the interaction between the nucleons. The stability of
a nucleus is quantified in terms of the half-life of its radioactive
decays such as α, β
±
, electron capture (EC) and spontaneous fis-
http://dx.doi.org/10.1016/j.physletb.2016.11.038
0370-2693/
© 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by
SCOAP
3
.