Collapse of the N=28 shell closure in (42)Si.
The energies of the excited states in very neutron-rich (42)Si and (41,43)P have been measured using in-beam gamma-ray spectroscopy from the fragmentation of secondary beams of (42,44)S at 39A MeV. The low 2(+) energy of (42)Si, 770(19) keV, together with the level schemes of (41,43)P, provides evidence for the disappearance of the Z=14 and N=28 spherical shell closures, which is ascribed mainly to the action of proton-neutron tensor forces. New shell model calculations indicate that (42)Si is best described as a well-deformed oblate rotor.
Bastin
B
B
Laboratoire de Physique Corpusculaire, 6, bd du Mal Juin, F-14050 Caen Cedex, France.
Grévy
S
S
Sohler
D
D
Sorlin
O
O
Dombrádi
Zs
Z
Achouri
N L
NL
Angélique
J C
JC
Azaiez
F
F
Baiborodin
D
D
Borcea
R
R
Bourgeois
C
C
Buta
A
A
Bürger
A
A
Chapman
R
R
Dalouzy
J C
JC
Dlouhy
Z
Z
Drouard
A
A
Elekes
Z
Z
Franchoo
S
S
Iacob
S
S
Laurent
B
B
Lazar
M
M
Liang
X
X
Liénard
E
E
Mrazek
J
J
Nalpas
L
L
Negoita
F
F
Orr
N A
NA
Penionzhkevich
Y
Y
Podolyák
Zs
Z
Pougheon
F
F
Roussel-Chomaz
P
P
Saint-Laurent
M G
MG
Stanoiu
M
M
Stefan
I
I
Nowacki
F
F
Poves
A
A