Autoionization and photoionization of O(D-1)

Abstract

Single-photon ionization of atomic singlet oxygen [O(D-1)] is investigated between 12 and 18 eV. O(D-1) is efficiently prepared by laser photolysis of ozone in the Hartley band regime (lambda = 270 nm). It is subsequently ionized by using monochromatic radiation, which is generated in a laser-produced plasma. Time-of-flight mass spectra are recorded and the photoion yield of O+ is measured. Direct photoionization of O(D-1) is not observed between the onset of the first (S-4(o)) and the second (D-2(o)) ionization threshold. Intense resonant features occur below the D-2(o) threshold. These are assigned to LS-forbidden autoionization of Rydberg singlet states by the S-4(o) continuum. The relative intensities of autoionization resonances are compared to the corresponding optical oscillator strengths. The results are discussed in terms of the autoionization efficiency of Rydberg states.