Investigation of auto-ionizing states in xenon by resonantly enhanced multi-photon ionization

We have examined the autoionization spectrum of xenon by resonantly enhanced three-photon ionization (2 + 1 REMPI) involving intermediate states 5p6p [J = 0, 2]. The properties of the observed autoionization resonances change significantly with the choice of the intermediate state. For ionization via an intermediate state with predominantly 5p(P3/2) core character, a strong continuum with embedded window-type 5p(P1/2)nd ′-autoionization resonances is observed. For intermediate states, predominantly with 5p(P1/2) core character, both 5p (P1/2)nd ′as well as 5p(P1/2)ns ′-resonances are present in the spectrum as overlapping, nearly symmetric peaks on a rather weak continuum. Calculations confirm the significant dependence of the spectral lineshapes upon the excitation pathway to the autoionizing state. The ionization data are compared with spectra obtained by monitoring third-harmonic generation via autoionizing states without resonant excitation of intermediate states. These spectra also exhibit the signature of both the nd′and ns′-resonances. PACS. 32.80.Dz Autoionization