  Absolute two-photon detachment cross sections and photoelectron angular
distribution are calculated for halogen negative ions within lowest-order
perturbation theory. The Dyson equation method is used to obtain the outer np
ground-state wave functions with proper asymptotic behavior exp (-k r),
corresponding to correct (experimental) binding energies E=k^2/2. The latter is
crucial for obtaining correct absolute values of the multiphoton cross sections
(Gribakin and Kuchiev 1997 Phys. Rev.A55 3760). Comparisons with previous
calculations and experimental data are performed.
