The "soft dipole" E1 strength function is calculated for the transition from
the 6He 0+ ground state to the 1− continuum 4He+n+n. The
calculations were performed within the hyperspherical harmonics formalism. The
sensitivity of the results to the 6He ground state structure and to final
state interactions, are analyzed. The large-basis calculations show the
reliably converged results for soft dipole strength function and for momentum
correlations of the ^{6}\mbox{He} \rightarrow \, ^{4}He+n+n dissociation
products. Transition mechanisms are analyzed based on the momentum
correlations. The comparison with experimental data is provided.Comment: 16 pages, 17 figure