Photoionization of C2+ ions (original) (raw)

Photoionisation of Ca + ions in the valence- energy region 20–56eV: experiment and theory

Relative cross sections for the valence shell photoionisation (PI) of S 2 ground level and D 2 metastable Ca + ions were measured with high energy resolution by using the ion–photon merged-beams technique at the Advanced Light Source. Overview measurements were performed with a full width at half maximum bandpass of E 17 D = meV, covering the energy range 20–56eV. Details of the PI spectrum were investigated at energy resolutions reaching the level of E 3.3 D = meV. The photon energy scale was calibrated with an uncertainty of ±5meV. By comparison with previous absolute measurements the present experimental high-resolution data were normalized to an absolute cross-section scale and the fraction of metastable Ca + ions that were present in the parent ion beam was determined to be 18% ±4%. Large-scale R-matrix calculations using the Dirac Coulomb approximation and employing 594 levels in the close-coupling expansion were performed for the s p s Ca 3 3 4 S 2 6 2 1 2 + ()and s p d Ca 3 3 3 D 2 6 2 3 2,5 2 + () levels. The experimental data are compared with the results of these calculations and previous theoretical and experimental studies.

The Absolute Cross Section forL‐Shell Photoionization of C+Ions from Threshold to 105 eV

The Astrophysical Journal Supplement Series, 2001

The absolute cross section for photoionization of C`ions has been measured from the ionization threshold at 24 eV to 105 eV by overlapping an ion beam with a monochromatized synchrotronradiation beam from the ASTRID undulator. The measurements, which are important for astrophysical modeling of, for example, stellar atmospheres, have been compared with R-matrix calculations from the Opacity Project and the Iron Project. The general agreement between theory and experiment is good, yet di †erences in the magnitude of the cross section of up to 50% are observed as well as some deviations concerning the resonance structure. Subject headings : atomic data È atomic processes

K-shell photoionization of Belike carbon ions: experiment and theory for C 2+

Journal of Physics B-atomic Molecular and Optical Physics, 2005

Absolute cross-section measurements for K-shell photoionization of Be-like C 2+ ions have been performed in the photon energy range 292-325 eV. These measurements have been made using the photon-ion merged-beam endstation at the Advanced Light Source, Lawrence Berkeley National Laboratory. Absolute measurements compared with theoretical results from the R-matrix method indicate that the primary C 2+ ion beam consisted of 62% groundstate (1s 2 2s 2 1 S) and 38% metastable state (1s 2 2s2p 3 P o ) ions. Reasonable agreement is seen between theory and experiment for absolute photoionization cross sections, resonance energies and autoionization linewidths of K-shellvacancy Auger states. 9 Present address:

Photoionization of C 2+ ions: time-reversed recombination of C 3+ with electrons

Journal of Physics B: Atomic, Molecular and Optical Physics, 2002

Absolute cross sections for the K-shell photoionization of ground-state Li-like carbon [C 3+ (1s 2 2s 2 S)] ions were measured by employing the ion-photon merged-beams technique at the Advanced Light Source. The energy ranges 299.8-300.15 eV, 303.29-303.58 eV and 335.61-337.57 eV of the [1s(2s2p) 3 P] 2 P, [1s(2s2p) 1 P] 2 P and [(1s2s) 3 S 3p] 2 P resonances, respectively, were investigated using resolving powers of up to 6000. The autoionization linewidth of the [1s(2s2p) 1 P] 2 P resonance was measured to be 27 ± 5 meV and compares favourably with a theoretical result of 26 meV obtained from the intermediate coupling R-matrix method. The present photoionization cross section results are compared with the outcome from photorecombination measurements by employing the principle of detailed balance.

Valence-shell photoionization of the Cℓ-like ion Ar + : Experiment and theory

Journal of Physics: Conference Series, 2009

Absolute cross-section measurements for valence-shell photoionization of Ar + ions are reported for photon energies ranging from 27.4 to 60.0 eV. The data, taken by merging beams of ions and synchrotron radiation at a photon energy resolution of 10 meV, indicate that the primary ion beam was a statistically weighted mixture of the 2 P o 3/2 ground state and the 2 P o 1/2 metastable state of Ar + . Photoionization of this Cl-like ion is characterized by multiple Rydberg series of autoionizing resonances superimposed on a direct photoionization continuum. Observed resonance line shapes indicate interference between indirect and direct photoionization channels. Resonance features are spectroscopically assigned and their energies and quantum defects are tabulated. The measurements are satisfactorily reproduced by theoretical calculations based on an intermediate coupling semirelativistic Breit-Pauli approximation.

Photoionization of ground and excited states of Ca+ and comparison along the isoelectronic sequence

Photoionization cross-section calculations are performed on the ground state ([Ne]3s 2 3p 6 4s 2 S e 1/2 ) and the first two excited states ([Ne]3s 2 3p 6 3d 2 D e 3/2 and [Ne]3s 2 3p 6 3d 2 D e 5/2 ) of Ca + ions for photon energies from threshold to 45.0 eV using the relativistic (Breit-Pauli) R-matrix method. The discrete Ca 2+ orbitals are generated using the computer program AUTOSTRUCTURE; 30 configurations are included in the configuration-interaction calculation for the states of Ca 2+ . The prominent 3p → 3d giant resonances are analyzed and identified, and our results are compared with experimental results, and rather good agreement is found. Using results of our previous photoionization calculations on Sc 2+ and Ti 3+ ions, the strongest and broadest resonances in the photoionization cross section of those three ions (Ca + , Sc 2+ , and Ti 3+ ), in terms of width and oscillator strengths, are compared to show the evolution as a function of nuclear charge.

Valence-shell photoionization of the chlorinelike Ca3+ ion

Absolute photoionization measurements were performed for a mixture of 2Po 3/2 ground-state and 2Po 1/2 metastable-state Ca3+ ions over the photon energy range 65.7–104.6 eV by merging an ion beam with a beam of monochromatized synchrotron radiation. The ionization threshold energy of the 2Po 3/2 ground state was measured to be 67.063 ± 0.015 eV, which is 0.207 eV lower than the value tabulated in the NIST database. Most of the observed resonances associated with multiple Rydberg series of autoionizing states have been assigned spectroscopically using the quantum defect form of the Rydberg formula, guided by relativistic Hartree-Fock calculations of resonance energies and oscillator strengths. Intermediate coupling R-matrix calculations performed using the semi-relativistic Breit-Pauli approximation are in suitable agreement with measured absolute photoionization cross section in the energy range studied for this complex Cl-like ion species.

Photodetachment of C− in the ground state

Journal of Physics: Conference Series, 2020

Synopsis Absolute total cross sections and asymmetry parameters for photodetachment of C− (4So) have been measured using animated-crossed-beam and velocity map imaging techniques, for photon energies from threshold up to 6eV. The cross sections are 15% to 25% larger than earlier experimental results above 2.2 eV. They are in very good agreement with those from a new R-matrix calculation using polarized pseudostates.

K-shell photodetachment fromC−:Experiment and theory

Physical Review A, 2003

K-shell photodetachment from C Ϫ has been investigated in the photon energy range between 280 and 285 eV using the merged ion-beam-photon-beam technique. C Ϫ ions were produced using a Cs sputtering negative-ion source, while the photons were produced by the undulator beam line 10.0.1 of the Advanced Light Source. C ϩ ions formed by double detachment were detected as a function of incident photon energy. Using this collinear arrangement, the relative cross sections were measured and compared with theoretical predictions. The measured spectrum shows the first experimental evidence of the 1s2s 2 2p 4 (4 P) shape resonance near 281.7 eV, which is in excellent agreement with two independent R-matrix calculations for the 1s photodetachment cross section of C Ϫ producing C ϩ .