Reduction of the spin-orbit splittings at the n = 28 shell closure.
The N = 28 shell closure has been investigated via the 46Ar(d,p)47Ar transfer reaction in inverse kinematics. Energies and spectroscopic factors of the neutron p(3/2), p(1/2), and f(5/2) states in 47Ar were determined and compared to those of the 49Ca isotone. We deduced a reduction of the N = 28 gap by 330(90) keV and spin-orbit weakenings of approximately 10(2) and 45(10)% for the f and p states, respectively. Such large variations for the f and p spin-orbit splittings could be accounted for by the proton-neutron tensor force and by the density dependence of the spin-orbit interaction, respectively. This contrasts with the picture of the spin-orbit interaction as a surface term only.
Gaudefroy
L
L
IPN, IN2P3-CNRS,F- 91406 Orsay Cedex, France.
Sorlin
O
O
Beaumel
D
D
Blumenfeld
Y
Y
Dombrádi
Z
Z
Fortier
S
S
Franchoo
S
S
Gélin
M
M
Gibelin
J
J
Grévy
S
S
Hammache
F
F
Ibrahim
F
F
Kemper
K W
KW
Kratz
K-L
KL
Lukyanov
S M
SM
Monrozeau
C
C
Nalpas
L
L
Nowacki
F
F
Ostrowski
A N
AN
Otsuka
T
T
Penionzhkevich
Yu-E
YE
Piekarewicz
J
J
Pollacco
E C
EC
Roussel-Chomaz
P
P
Rich
E
E
Scarpaci
J A
JA
St Laurent
M G
MG
Sohler
D
D
Stanoiu
M
M
Suzuki
T
T
Tryggestad
E
E
Verney
D
D