The concept of a Pauli barrier in nucleus-nucleus scattering

Abstract

The influence of partly Pauli-forbidden states on the width of resonances is studied in the context of the fish bone optical model. A numerical study of ~-e and c~-160 scattering shows that the part of the nontocal interaction of the model which is due to the partly forbidden states represents a Pauli barrier which inhibits transitions between the inner and asymptotic regions and increases the lifetime of resonances.

Equivalent local potential for the fish bone optical potential by inversion of its phase shifts

“…We consider the case of a-160 at Ecru=30, 40 and 50 MeV in the fish bone optical model with parameters given in [23]. and t60 the common harmonic oscillator width parameter a=0.32fm -z is assumed, which means that the norm kernel eigenstates are harmonic oscillator functions of width parameter 0.512 fm -2.. For comparison with previous results we also neglect the imaginary part of the potential [23], which is of lesser importance for our purpose, namely the investigation of the consequences of the Pauli principle in the context of the fish bone optical model.…”

“…Similar conclusions were drawn by Tohsaki-Suzuki et al [27] in 160-160 scattering. It was shown by Schmid et al [23] for c~-c~ and c~ -160 scattering, in the context of the fish bone optical model, that particularly the partly Pauli forbidden states manifest themselves as a barrier (the "Pauli barrier") in the surface region of the corresponding trivially equivalent local potential. Such Pauli barriers were shown to exist (between 4 and 7 fm) for c~-160 scattering at the resonances of the 0-rotational band.…”

“…A further advantage consists in the clear separation between the nonlocal part, containing all effects of the Pauli principle, and the local (optical) part of the fish bone model. Schmid et al [23] recently found that the Pauli forbidden states and particularly the partly Pauli forbidden states, may act like a barrier in the surface region, thereby increasing the lifetime of the resonances. This was shown by comparing the trivially local equivalent potential of the full fish bone optical potential with the purely local part of the latter.…”

Coupling to two target-state bands in the study of then+Ne22system at low energy

“…To first order, and without consideration of band quantum numbers, a collective (rotational) model gives B(E2) that are proportional to β For a scattering nucleon impinging upon a partiallyfilled shell of a target nucleus, the Pauli principle does not necessarily imply a binary rule -that the shell is completely open or completely blocked [25][26][27][28][29][30][31]. We label as Pauli hindrance the intermediate situation, where the present nucleons do not completely, but only partially block additional nucleons.…”

The non-orthogonality problem of the coupled reaction channels method

“…The example, however, overestimates the need for distortions and more numerical tests are desirable. An equation with a mathematical structure similar to (15) has been solved in the context of the fish bone model [11] without encountering numerical difficulties; the e-technique, in special, has proved to be very useful.…”