Measurement of the four-photon detachment cross section of cl− at 1.064,μm

An accelerated beam of Cl⁻ ions is photodetached by a single-mode Nd:YAG laser, and the resulting neutrals aredetected. By measuring the saturationintensity of this process, one derives the cross section for four-photondetachment. This cross section is smaller by a factor of 6 than a recently calculated value. Comparison of thephotodetachment saturation intensity of Cl⁻ with those of other halogen negative ions shows that this correspondsto regular behavior among the halogen elements, suggesting limitations in the theoretical models.