K-shell photoionization of B-like oxygen (O^{3 +}) ions: experiment and theory

Abstract

Absolute cross sections for the K-shell photoionization of boron-like (B-like) O 3+ ions were measured by employing the ion-photon merged-beam technique at the SOLEIL synchrotron-radiation facility in Saint-Aubin, France. High-resolution spectroscopy with E/ E ≈5000 (≈110 meV, full width half maximum) was achieved with photon energy from 540 up to 600 eV. Several theoretical approaches, including R-matrix, multi-configuration Dirac-Fock and screening constant by unit nuclear charge were used to identify and characterize the strong 1s → 2p and the weaker 1s → 3p resonances observed in the K-shell spectra of this ion. The trend of the integrated oscillator strength and autoionization width (natural line width) of the strong 1s → 2p resonances along the first few ions of the B-like sequence is discussed.

K-shell photoionization of O4 +and O5 +ions: experiment and theory

“…The K-shell photoionization cross section of the neutral oxygen atom measured by Stolte et al [25,26] at the Advanced Light Source (ALS) gives a position for this line almost 0.8 eV lower than the energy deduced from Chandra observations [24], a difference distinctly outside the quoted uncertainties of both measurements. Similar disagreement was found between our previous measurements at SOLEIL and the Chandra and XMM Newton observations for the O 3+ ion [9]. We have taken special care in the present work of the energy calibration for the experimental spectra to verify if such discrepancies exist also for O + and O 2+ ions.…”

“…This work is a continuation of our previous study on the O 3+ ion [9]. As the ions were produced in an electron cyclotron resonance ion source (ECRIS), both ions in their respective ground and metastable states contributed to the experimental spectra.…”

“…Marked discrepancies were recently noted between the energies measured by synchrotron radiation based experiments for neutral oxygen [26] and the O 3+ ion [9] and x-ray satellite observations [5,24]. The energies of the 1s → 2p transitions for the first members of the oxygen isonuclear series as determined by Chandra observations and SR experiments are summarized in Table VI.…”

“…The energies of the 1s → 2p transitions for the first members of the oxygen isonuclear series as determined by Chandra observations and SR experiments are summarized in Table VI. For the O 3+ ion, energies measured at SOLEIL with our merged-beam experiment [9] have been recalibrated using the revised photon energy calibration (see Sec. IIC) which we believe to be more reliable.…”

“…The merged-beam technique was used at Spring-8 to measure, with a low resolving power (E/ E ≈ 310), relative K-shell resonant photoionization cross sections for O + ions in the photon energy range of the 1s → 2p photoexcitations [23]. Recently, we published high-resolution (≈5000 resolving power) absolute measurements performed at SOLEIL of the photoionization cross section for the O 3+ ion in the energy range of the 1s → 2p and 1s → 3p photoexcitations [9].…”