Shape coexistence near neutron number N=20: first identification of the E0 decay from the deformed first excited Jpi=0+ state in 30Mg.
The 1789 keV state in 30Mg was identified as the first excited 0+ state via its electric monopole (E0) transition to the ground state. The measured small value of rho2(E0,0(2)+-->0(1)+)=(26.2+/-7.5)x10(-3) implies within a two-level model a small mixing of competing configurations with largely different intrinsic quadrupole deformation near the neutron shell closure at N=20. Axially symmetric configuration mixing calculations identify the ground state of 30Mg to be based on neutron configurations below the N=20 shell closure, while the excited 0+ state mainly consists of two neutrons excited into the nu 1f7/2 orbital. The experimental result represents the first case where an E0 back decay from a strongly deformed second to the normal deformed first nuclear potential minimum well has been unambiguously identified, thus directly proving shape coexistence at the borderline of the much-debated "island of inversion."
Schwerdtfeger
W
W
Ludwig-Maximilians-Universität München, D-85748 Garching, Germany.
Thirolf
P G
PG
Wimmer
K
K
Habs
D
D
Mach
H
H
Rodriguez
T R
TR
Bildstein
V
V
Egido
J L
JL
Fraile
L M
LM
Gernhäuser
R
R
Hertenberger
R
R
Heyde
K
K
Hoff
P
P
Hübel
H
H
Köster
U
U
Kröll
T
T
Krücken
R
R
Lutter
R
R
Morgan
T
T
Ring
P
P