The usual shell-model treatment of the nuclear scattering of high-energy electrons neglects the motion of the center of mass of the nucleus. The correction due to this is calculated for the case of an oscillator potential well and gives a simple additional factor multiplying the nuclear form factor. S CHIFF'S calculations 1 of the cross section for scattering of high-energy electrons from nuclei have been extended in two respects. Firstly nonrelativistic recoil of the nucleus is included, and secondly the charge and current densities are treated as operators connecting states of the nucleus described by the shell model, for which an oscillator potential well is assumed. Other approximations used by Schiff are used here, such as Born approximation and use of the Moller fields, and exchange currents are neglected. The calculations are particularly relevant for light nuclei.In the laboratory system, the interaction energy between electron and nucleus is described bywhere hco is the loss of energy of the electron, which differs from the excitation energy of the nucleus. We follow Schiff in breaking up H' into electric and magnetic multipole terms of all orders, with the expansion performed about the center of mass of the nucleus, in which case a recoil-current term can be separated out in H r . For electric multipole transitions with no change in the z component of the nuclear spin, which are the only ones to contribute to elastic scattering from a nucleus with zero spin, one finds, with Schiff's notation, 1

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A model in which a baryon can be regarded as a bound state of two particles has been generalized to be approximately invariant under SU{6). In the model, one of the constituent particles of a baryon can be regarded as a quark and the other particle can be considered as a tightly bound state of two quarks, or diquark. The quark is taken to belong to a six-dimensional representation of SU{6), while the diquark is taken to belong to a twenty-one-dimensional representation. With this model, which can be considered as a specific dynamical approximation to the three-quark model, the baryon medium-strong mass splittings are calculated beyond lowest-order perturbation theory. The model provides a mechanism for breaking the Gell-Mann-Okubo baryon-octet mass formula while breaking the baryon-decuplet equal-spacing rule by a smaller amount.

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