Electron correlation in double photoexcitation of H 2 S as studied by H( 2 p ) formation: Comparison with H 2 O

Superexcited states of ${\mathrm{H}}_{2}\mathrm{S}$ have been investigated with determining the cross sections for emission of dispersed and nondispersed atomic fluorescence against the incident photon energy in the range 11--40 eV to address the ionization and excitation of the valence electrons. This method enables us to extract the discrete electronic state from the superposition with continuous electronic states. The cross sections for H($2p$) formation have been put on an absolute scale. Ten superexcited states have been found, two in the range 13--15 eV are singly excited $2{b}_{2}^{\ensuremath{-}1}$(mo) states with a single configuration and the other eight states in the range 16--25 eV are doubly excited states with multiple configurations. State-resolved dipole oscillator strengths for H($2p$) formation in the photoexcitation of ${\mathrm{H}}_{2}\mathrm{S}$ have been determined. Similar experiments have been performed for ${\mathrm{H}}_{2}\mathrm{O}$. The state-resolved dipole oscillator strengths for H($2p$) formation in the photoexcitation of ${\mathrm{H}}_{2}\mathrm{S}$ are $\ensuremath{\sim}{10}^{\ensuremath{-}3}$, whereas those in the photoexcitation of ${\mathrm{H}}_{2}\mathrm{O}$ range from $\ensuremath{\sim}{10}^{\ensuremath{-}3}$ to $\ensuremath{\sim}{10}^{\ensuremath{-}2}$. It is found that major fragment atoms are H($2p$) atoms in the photoexcitation of ${\mathrm{H}}_{2}\mathrm{O}$ and ${\mathrm{S}}^{*}$ in the photoexcitation of ${\mathrm{H}}_{2}\mathrm{S}$. The superexcited states of ${\mathrm{H}}_{2}\mathrm{O}$ and ${\mathrm{H}}_{2}\mathrm{S}$ are compared based on the similarity and difference of the electronic structures. It turns out from the comparison that (i) the smaller values of the dipole oscillator strengths for H($2p$) formation in the photoexcitation of ${\mathrm{H}}_{2}\mathrm{S}$ are related to the change of the major fragment atoms and (ii) the energy splitting of the doubly excited ``$4{a}_{1}^{\ensuremath{-}1}({\text{mo}}^{\ensuremath{'}})$'' states of ${\mathrm{H}}_{2}\mathrm{S}$ is enhanced in comparison with that of the doubly excited ``$2{a}_{1}^{\ensuremath{-}1}({\text{mo}}^{\ensuremath{'}})$'' states of ${\mathrm{H}}_{2}\mathrm{O}$. This enhancement is caused by the stronger electron correlation in ${\mathrm{H}}_{2}\mathrm{S}$ than in ${\mathrm{H}}_{2}\mathrm{O}$. The similarity in shape is indicated between the inner valence band and inner shell band in the fluorescence cross sections against the incident photon energy for ${\mathrm{H}}_{2}\mathrm{S}$ and ${\mathrm{H}}_{2}\mathrm{O}$.