Observation of the [1s2s](^3,1S)nln^′l^{′ 1}P inner-shell doubly excited states of Ne by photoion yield spectroscopy

The photoabsorption spectrum of Ne in the excitation energy region of the [1s2s](^3,1S)nln^′l^′ doubly excited states has been measured using high brilliant soft x-ray undulator radiation, where square brackets indicate hole states. The observed absorption spectrum was analyzed with the aid of theoretical calculations based on the multiconfiguration Dirac-Fock (MCDF) method. The computation has revealed that the observed features are successfully assigned with several series of the resonant double excitations, such as the [1s2s](^3,1S)3snp (3⩽n⩽6) and the [1s2s](³S)3pns (4⩽n⩽6) series. The [1s2s]nln^′l^′ double excitation resonance leading to the lowest [1s2s](³S)3s3p state was analyzed using the well-known parametrized Fano profile. The energy as well as the width of the resonance for such highly correlated multiply excited state have been determined and the possible decay channels for the [1s2s](³S)3s3p state were also discussed.