Polarized-proton scattering by even-mass germanium and selenium isotopes at 22 MeV incident energy

Moonen, Whl Wim; Hall, van Pj Piet; Klein, S.S.; Nijgh, G.J.; Overveld, van Cwam Kees; Petit, Rmal Rita; Poppema, OJ Okko

doi:10.1088/0954-3899/19/4/018

Cited by 13 publications

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References 41 publications

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“…We have found data for the scattering of 22.3 MeV protons from both 76 Ge and 76 Se [28] and for 64.5 MeV proton scattering from 76 Se [29] (see fig. 2).…”

Section: Resultsmentioning

confidence: 96%

Charge-exchange reaction cross sections and the Gamow-Teller strength for double β decay

2007

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The proportionality between single charge-exchange reaction cross sections in the forward direction as found, for example from (p, n) and ( 3 He,t) and from (n, p) and (d, 2 He) reactions, and the Gamow-Teller (GT) strength into the same final nuclear states has been studied and/or assumed often in the past. Using the most physically justified theory we have at our disposal and for the specific example of the 76 Ge-76 Se system that may undergo double beta-decay, we demonstrate that the proportionality is a relative good assumption for reactions changing a neutron into a proton, i.e. 76 Ge(p, n) 76 As. In this channel, the main contribution to the GT strengths comes from the removal of a neutron from an occupied single-particle (SP) state and putting a proton into an unoccupied SP state having either the same state quantum numbers or those of the spin-orbit partner. In contrast to this, in the second leg of the double beta decay a single proton must be taken from an occupied SP state and a neutron placed in an unoccupied one. This second process often is Pauli forbidden in medium-heavy nuclei and only can be effected if the Fermi surface is smeared out. Such is the case for 76 Se(n, p) 76 As. Our results suggest that one may not always assume a proportionality between the forward-angle cross sections of the charge-exchange reactions and the GT strength in any such medium-heavy nuclei. The discrepancy originates from a pronounced effect of the radial dependence of the nucleon-nucleon (N N ) interaction in connection with the Pauli principle on the cross sections in the (n, p) reaction channel. Such a radial dependence is completely absent in the GT transition operator.

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“…We have found data for the scattering of 22.3 MeV protons from both 76 Ge and 76 Se [28] and for 64.5 MeV proton scattering from 76 Se [29] (see fig. 2).…”

Section: Resultsmentioning

confidence: 96%