Dae-Soung Kim

Autoionizing resonances in the photoionization of ground state atomic magnesium

Photoionization of the ground state 1s22s22p63s2 1S of atomic magnesium is studied theoretically in the energy region between the Mg+(3s) and Mg+(4p) thresholds using the non-iterative variational R-matrix method combined with multichannel quantum defect theory at the R-matrix surface. The initial and final states are represented by configuration-interaction wavefunctions. We calculated total and partial photoionization cross sections in both length and velocity formulations. Photoionization cross sections are dominated by Rydberg series of autoionization resonances converging to Mg+(3p, 4s, 3d and 4p) thresholds. We also calculated the photoelectron angular distribution asymmetry parameter β for the process leaving the ion in the Mg+(3p) state. The present photoionization cross sections are in good agreement with available experiments and previous calculations. There is excellent agreement between length and velocity gauges in our calculation.

Photoionization of the Be-like O4 + ion: total and partial cross sections for the ground 2s2 1S and excited 2s2p 1, 3P states

Photoionization cross sections of the Be-like O4 + ion in the photon energy region from the first threshold up to the O5 + 3d threshold have been calculated using a non-iterative variational R-matrix method combined with multichannel quantum-defect theory for the ground 2s2 1S and excited 2s2p 1, 3P states. The partial cross sections are presented and the autoionizing resonance structures arising from the ground and excited states are identified and characterized. Our calculational results, which show excellent agreement between length and velocity gauges, are compared with the available experiment and previous calculations, and good agreement is found.

Photodetachment of in the vicinity of the 1s threshold

A study of the photodetachment of the metastable state of using multiconfiguration Hartree - Fock (MCHF) wavefunctions for bound states and Hartree - Fock plus configuration-interaction (HF + CI) continuum wavefunctions has revealed that the cross section is dominated by three features in the vicinity of the 1s threshold: a huge (hollow ion) resonance just below threshold; a large 30 Mb peak due to 1s detachment just above threshold and 1s detachment plus excitation a little way above threshold. No experimental investigation of this phenomenology, which differs markedly from 1s photoabsorption in neutral atoms, exists.

Irregularity of Autoionizing Rydberg Series in Photoionization Leading to the Si3+ 3l States from the Mg-Like Si2+ Ions

We report the theoretical photoionization cross sections in the low energy region for Mg-like Si 2+ ion, with arousing desire for experiments. With the advent of third-generation synchrotron radiation sources, it is expected to study for this ionic system using merged-beam technique. Since the Mg-like Si 2+ ions are expected to be admixed with the ground-state and several low-lying excited-states, we have calculated the photoionization cross sections from the initial ground-state 3 s 2 1 S , and the excited-states 3 s 3 p 1,3 P , 3 s 3 d 1,3 D , and 3 s 4 s 1,3 S of Mg-like Si 2+ ion. For these calculations, we have used a most elaborate noniterative eigenchannel R -matrix method. We briefly discuss the results for autoionizing resonances and interlopers in the structure of photoionization cross sections, and compare with the previous results of Opacity Project.

Theoretical photoionization spectra in the UV photon energy range for a Mg-like Al+ ion

In the present work, we report the photoionization cross sections of the Al+ ion calculated for the photon energy range 20–26 eV and 30–50 eV. We have expanded our previous calculation (2007 J. Phys. Soc. Japan 76 014302) with an optimized admixture of the initial ground state 3s21S and exited states 3s3p1,3P, 3s3d1,3D and 3s4s1,3S, and obtained significantly improved predictions for the main background and autoionizing resonance structures of the reported experimental spectra. The absolute measurements of the photoionization cross sections of the Al+ ion in these energy ranges have been performed by West et al (2001 Phys. Rev. A 63 052719), and they reported that the prominent peaks around 21 eV were attributed to the effects of the significant influence of the small fraction of the fourth-order radiation with energies around 84 eV from the synchrotron source. In our previous work, the main shape for these cross sections was calculated assuming an admixture of initial 3s21S and 3s3p3P states, only with a rough overall estimate for the experimental spectra in the photon energy range 20–26 eV, and without these peaks around 21 eV. The report of the experimental assignment attributes these peaks to the excitation of a 2p electron from the core. However, our present results with the new admixture reveal similar peaks without considering the possibility of the core excitation.

Photoionization Leading to the Al2+ 3l States from the Ground State of Mg-like Al+ Ion

Photoionization cross sections leading to the Al 2+ 3 l states from the 1 S ground state of the Mg-like Al + have been calculated using the eigenchannel R -matrix method. The calculations have been performed in L S coupling using a configuration interaction for the target states as well as for the full atomic wave functions. The lower members of autoionizing Rydberg series converging to the Al 2+ 3 l thresholds are identified. The present calculations with good agreement between length and velocity gauges are compared with the available previous results of the Opacity Project and experimental measurements.

Photoionization of the excited 3s3p?1,3Po states of atomic magnesium

Calculational results for the photoionization cross sections leading to the ionic Mg+(\rm3s,3p,4s and 3d) states from the excited 3s3p?1,3Po states of atomic magnesium are reported in the energy region from the first ionization threshold up to the Mg+(4p) threshold limit. For these calculations, we have used an enhanced non-iterative variational R-matrix approach combined with multichannel quantum-defect theory at the R-matrix surface. Autoionizing doubly excited 1,3S, 1,3P and 1,3D resonance structures converging to the Mg+(3p, 4s, 3d and 4p) thresholds are discussed with resonant energies Er, effective quantum numbers n* and widths ?. The present photoionization cross sections are in good agreement with previous available calculations. There is excellent agreement between length and velocity gauges in our calculations.

Photoionization of the ground-state Be-like B+ ion leading to the n = 2 and n = 3 states of B2+

A theoretical study of the photoionization of the 1S ground state of Be-like B+ ion leading to the 2s, 2p, 3s and 3p states of B2+ has been performed using a noniterative eigenchannel R-matrix method. The autoionizing Rydberg series which converge to the various levels of B2+ limits up to 3d are identified and characterized. In addition, a calculation of the photoionization of the 2s2p 3Po metastable state of B+ ion was performed to compare the results with recent work on the photoionization of a mixture of ground and metastable states of the B+ ion. Excellent agreement with recent experiment and associated theory in the photon energy range 22–31.3 eV was found. The present calculation is also in overall reasonable agreement with a previous Opacity Project (OP) calculation, and excellent agreement between length and velocity gauges is found.

Characteristics of photoionization in the XUV domain for the excited 1s22s2p1,3Po states of the Be-like C2+ ion

Resonance structures and their characteristics in the photoionization of the first excited p-states of Be-like C2+ ion which interact with the even-parity continua have been studied up to the C3+ 3d threshold limit. Using the variational R-matrix method, calculations have been performed in the initial 20 and final 22 state close-coupling approximations in the photon wavelength range 15–35 nm. The detailed photoionization processes of included multichannels are displayed in the partial photoionization cross sections, which contain a number of autoionizing Rydberg series of resonances converging to the C3+ 2p, 3s, 3p and 3d thresholds. In particular, the lower members of the Rydberg series showing irregular patterns of resonances, which lie above the C3+ 2p threshold, are identified and resonance positions Er, effective quantum numbers n*, and widths Γ are presented. Excellent agreement between length and velocity gauge results is found, along with overall good agreement with previous work, except for the discrepancies with the threshold behaviour of the OP (opacity project) result.

Theoretical study of the photoionization of the excited 1 s 2 2 s 2 p P o 1 , 3 states of the Be -like B + ion

Photoionization of the first excited