  In this work, we present a new approximate method for obtaining simple wave
functions and effective operators for the ground state of exotic nuclei with a
neutron halo. We treat the core and halo as inert objects in a two-cluster
model. The relative wave function is a combination of simple harmonic
oscillator states with a size that is determined from a relation between the
nuclear radius and separation energy. Since these wave functions lack the
expected exponential decay, we apply a multiplicative renormalization to the
radial part of the operators, determined from the nuclear root-mean-square
radius. This combination of oscillator wavefunctions and renormalized operators
is then applied to the calculation of dipole strength distributions
$dB(E1,\varepsilon)/d\varepsilon$ for several $1n$- and $2n$-halo nuclei. By
fitting a single free parameter, the results show excellent agreement with the
available experimental data.
