70
E. V. Chimanski et al.
Fig. 1 Strength function for
a collective (low energy)
excited 3 − state of 56 Ni. The
histogram represents the
contribution of a particular
p-h mode, shown as the solid
vertical line E ph = 12.0 MeV,
along the RPA energy states.
The parameters of the curves
are given in the text
10 20 30 40 50 60 70 80
E x (MeV)
10 −7
10 −5
10 −3
10 −1
10 1
|a x
ph | 2
G
BW
Exp
Fig. 2 Two general fits for
the strength function of
Fig. 1. The constants and
linear coefficients are given in
the text
25 50 75 100 125 150 175 200
E x (MeV)
10 −8
10 −6
10 −4
10 −2
10 0
|a x
ph | 2
K
F
serves to calculate the particle–hole transition matrix elements for the cross-section
formula over a wide range of excitation energies and angular momenta.
4 Conclusions
The RPA strength function was studied for the 3 − collective states of 56 Ni. In this
case, its width accounts for the particle–hole configuration mixing present in the
state. The strength function for low-energy p-h components can be a complicated
function of excitation energy. The presence of a very long tail toward high energetic
states reflects the importance of those components in the description of decay transitions. We found that the combination of a Gaussian distribution with a Breit–Wigner
or an exponential produces good agreement with the histogram data. Collective
states present properties that are difficult to be taken into account statistically,