Interference Effects in the Resonant Photoemission Channels to the ${\mathrm{N}\mathrm{e}}^{+}$ $2p^4({}^{1}D_2)3p$ ${}^{2}P$, ${}^{2}D$, and ${}^{2}F$ States in the Ne $1s$ Excitation Region

We present measurements of total and partial photoionization cross sections of Ne in the $1s$ excitation region. The total cross section exhibits resonances with symmetric profiles, whereas the branching ratios to the ${\mathrm{N}\mathrm{e}}^{+}$ $2p^4({}^{1}D_2)3p$ ${}^{2}P$, ${}^{2}D$, and ${}^{2}F$ states present strong oscillations in the interresonance regions. We prove that not only the interference between the direct and resonant ionization processes but also the interference among the ionization processes via different nonisolated resonances are important for this effect.

Figure 1

Circles: measured total cross section for photoionization of Ne in the energy region of the $1s$ excitations. Thick line: least-${\chi }^2$ fit based on Lorentzian profiles, convoluted with a Gaussian profile with FWHM fixed to 66 meV. Thin lines: contributions from the individual resonances, before the convolution.

Figure 2

Angle-integrated electron spectra measured at the photon energies of (a) 868.42 and (b) 868.23 eV, together with the fit by Gaussian profiles.

Figure 3

(a) Measurements of the partial cross sections to $2p^4({}^{1}D_2)3p$ ${}^{2}P$, ${}^{2}D$, and ${}^{2}F$ together with the fit of individual components. (b) Branching ratios extracted from the measured electron spectra (points), and from the corresponding fit (lines). (c) Contributions of ${\sigma }_{\mathrm{r}\mathrm{e}\mathrm{s}\mathrm{\text{−}}\mathrm{r}\mathrm{e}\mathrm{s}}$ and ${\sigma }_{\mathrm{d}\mathrm{i}\mathrm{r}\mathrm{\text{−}}\mathrm{r}\mathrm{e}\mathrm{s}}$ as extracted from the analysis of the partial cross sections for the ${}^{2}P$ and ${}^{2}F$ states.