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Previous results for the pair production probability in a strong electric field with a finite longitudinal separation are generalized to the case of a finitelength flux tube with transverse confinement. The threshold length of the flux tube, below which pair production cannot occur, increases as a result of transverse confinement.

We review the rationale for basing the calculation of collective motion on the periodic solutions of the time-dependent Hartree-Fock mean field. With suitable discretization, we find a family of these solutions and we apply a simple quantization rule. Results are presented for 4 He and 16 O. ͓S0556-2813͑99͒04009-1͔