Role of multi-step processes in
at 41.25 MeV
N. Ikeda1 - F. Nakamura1 - Y. Inotani1 - K. Koga1 - M. Koga1 - S. Koto1 - T. Sugimitsu1 - H. Fujita2 - S. Morinobu1
1 Department of Physics, Kyushu University,
Fukuoka 812-8581, Japan
2 Daiichi College of Pharmaceutical Sciences, Fukuoka 815-8511, Japan
ikeda@kutl.kyushu-u.ac.jp
Received: 3 July 2000 / Revised version: 4 September 2000
Communicated by D. Guerreau
Abstract
The 16O(11B,12C)15N reaction at 41.25 MeV
has been investigated using the kinematical coincidence method.
Polarization tensors t20 and t40 of 12C[2+1]
for the quantization axis taken along the direction of propagation
have been measured at center-of-mass angles (
)
between 48
and 62
by analyzing the energy spectrum
of 12C[2+1] modulated by the effect of 
-ray emission.
The cross-sections of the transfer reactions leading to the
12C[g.s.]+15N[g.s.], 12C[2+1]+15N[g.s.]
and 12C[g.s.]+15N[3/2-1] final states
have also been measured in the range
48
120.
The polarization tensor terms of 12C[2+1] largely
deviating from zero have been observed, contrary to
the prediction by the distorted-wave Born approximation (DWBA).
The one-step DWBA calculation also fails in describing the transfer
reaction cross-sections.
It is shown that the coupled channel model calculation
including excitations and reorientations in 11B and 12C
satisfactorily reproduces both the tensor terms and the
cross-sections of the transfer reactions.
The multi-step processes passing through the excited states of
11B are found to significantly contribute to the reaction.
PACS
25.70.Hi Transfer reactions -
24.70.+s Polarization phenomena in reactions -
24.10.Eq Coupled-channel and distorted-wave models
Copyright Società Italiana di Fisica, Springer-Verlag 2000
