Study of nonradiative decay properties following resonant double excitation to the [1s2p]nln′l′ states of Ne atom using soft X-ray undulator radiation

We investigate the nonradiative decay properties of resonantly photoexcited [1s2p]nln′l′ (n,n′≧3) states of Ne atom, where square brackets indicate hole states, using soft X-ray undulator radiation. Partial ion-yield spectra for the Ne2+-Ne4+ ions were measured in the region of double excitation resonance by means of time-of-flight spectrometry. The Ne3+ partial ion-yield spectrum has been found to reveal resonant enhancements at the energy positions of doubly excited states, which implies the most plausible decay channels leading to the third step Auger processes. Energy diagram of the excited and relaxed states associated with the [1s2p](3P)3p2 doubly excited state of the neutral Ne as well as the Ne ions was calculated based on the multiconfiguration Dirac-Fock (MCDF) method in order to interpret the possible nonradiative decay channels. The low-energy electron spectrum originated from the second/third step Auger processes was preliminarily measured to show a rich structure induced at the [1s2p](3P)3p2 double excitation resonance.