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An attempt was made to find the very neutron-rich isotope 21 B among the fragmentation of a 94A MeV 40 Ar beam. Evidence for the particle instability of 21 B was obtained. As part of the search, the production cross sections of 13 light neutron-rich nuclei with Be and Ta targets are presented and compared to previous data. A large enhancement of the production cross sections for a Ta target is shown and a clear energy dependence of the production cross sections is shown for very neutron-rich nuclei.

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Kanungo et al. ReplyThe Letter by Kanungo et al. [1] begins by highlighting the most important problem concerning the 23 O nucleus, i.e., the interaction cross section ( I ) cannot be explained using a usual shell model structure for 23 O but can only be understood under extreme assumptions of a very long density tail.It also shows that the one neutron removal momentum distribution (P jj ÿn ) can be understood with the usual shell model configuration of 23 O as well as other configurations. The most important fact is that both the (P jj ÿn ) and ( I ) cannot be consistently explained within any model.It must be clarified here that as stated in the Comment [2], the model used by us is not an inert core-plus-neutron model because the core excited state is considered.It should be further clarified that the reaction theory used for the calculation of single-particle removal cross sections ( sp ) in the Comment [3,4] is the same as that employed by us and is described in Ref. [5].Reference [3] (and [4] therein) clearly shows the use of the core-plus-neutron model and has Eqs. (2) and (3) which are identical to those of Ref.[5], Table I. The Comment then takes a sum of these sp weighted by spectroscopic factors (C 2 S) calculated in a many body shell model.One difference between our calculation and that of the Comment is that the Comment includes the ground state and all possible calculated bound excited states. We on the other hand consider only the first excited state of 22 O and the ground state.The other difference is that since the Comment employs the many body shell model for the calculation of spectroscopic factors such factors are greater than unity. In contrast, we discuss s and d wave strengths that add up to unity since the reaction model used is a core-plusneutron one.A spectroscopic factor greater than unity can arise in reality and also in the many body shell model when we discuss the knockout of neutrons from nuclei with more than one neutron in the valence orbit. However, the present reaction model treats this system as a core one neutron. The correct model to explain such a system is that of core multineutron which, as we pointed out, is lacking. The Comment claims to have a well-developed reaction model, but does not show it being a core multineutron one. If they wish to use spectroscopic factors from the shell model then, to be consistent, it is better to use sp calculated from a core multineutron model which should be different from the present ones.The Comment does not discuss at all the interaction cross section with their model. To establish the success of their model, they should be able to reproduce all observables of 23 O. Incidentally Fig. 29 in a recent review by Brown [6] shows that the interaction cross section for 23 O is not reproduced in the shell model employed. So the essential problem concerning this nucleus addressed in the Letter is not solved in their model.