Two-photon detachment from the negative ions F^- and I^-: angular distributions with elliptically polarised light

Angular distributions of multiphoton detached electrons enable the determination of the relative amplitudes of the different channels allowed in the photodetachment process. Though detachment from a negative ion can be represented in the plane-wave approximation with real amplitudes, there are some unknown phases that can only be measured through multiphoton excitation with elliptically polarised light. The experiment is performed using an ion beam of either F ^- or I^- with light of various ellipticities (λ = 532 nm). Four real parameters can be extracted from the angular distributions. Their measured values show a qualitative difference between fluorine and iodine.