With a time-of-flight (TOF) ion analyzer combined with synchrotron radiation, total photoion-yield spectrum has been measured on isolated Mn atoms in the 2p → 3d excitation region (632 eV to 657 eV) with an estimated resolution 0.065 eV. The analysis of the observed spectrum was performed with the help of ab initio calculations of the excited states using the computer code GRASP92 for the MCDF calculation and of oscillator strengths for the excitation using the related REOS program. The calculations were performed for two outer-shell configuration cases: one considering the single reference-configuration 3dm4s2 and another with the multiple reference-configuration 3dm4s2 + 3dm + 14s + 3dm + 2 (m = 5 for the ground state and m = 6 for the 2p → 3d excited states). This two-step calculation showed the CI effect in the case of the excitation of a deep inner-shell.

Using the charge-separated photoion-yield method combined with monochromatized synchrotron radiation, single (M+) and double (M2+) photoionization spectra in the 3p excitation region were observed for isolated atoms M = Cr, Mn and Fe. The relaxation processes of excited states to double ionization, as well as to single ionization, were considered with the help of existing photoabsorption and photoelectron data and some calculations of highly-excited states of M+ using the atomic code GRASP92. In the 3p→3d giant resonance region before the 3p→n(s, d) Rydberg series starts, the spectral features in the M2+ channel are similar to those in the M+ channel. The ratios M2+/M+ in this region are rather constant accordingly against the photon energy with values 0.045 ± 0.005 for Cr, 0.17 ± 0.03 for Mn and 0.30 ± 0.08 for Fe at the giant resonance. The increase in the M2+/M+ ratio with increasing the atomic number Z can be explained by the increasing contribution of two-step double ionization via highly-excited M+ states. It is expected that, at the 3p→3d giant resonance, the one-step double ionization process occurs within a few per cent of the entire decay.

A series of time-of-flight (TOF) spectra of isolated Mn atoms were measured in the vicinity of 2p → 3d excitation states (635 to 656 eV) at a high-energy resolution. Synchrotron radiation was used as a light source. From this spectral data, charge-separated photoion-yield spectra and charge-state distribution as functions of the photon energy were obtained. The photoions resulting from the 2p → 3d excitation states are distributed from Mn + to Mn 6+ , with the largest component being Mn 3+ ions. Based on these spectra, the relaxation processes of the 2p → 3d excitation states are semi-quantitatively considered. For this purpose, highly excited states above the next ionization limit were calculated using the GRASP92 atomic code. It is found that single and double Auger shake-off processes play a central role in the formation of Mn 5+ and Mn 6+ ions. From the behavior of the charge-state distribution, the lowest 2p ionization limit has been determined to be 647.0 ± 0.3 eV.