Photoionization of C2+ ions (original) (raw)
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 .
Photoionization of Multiply Charged Ions at the Advanced Light Source
AIP Conference Proceedings, 2005
Photoionization of multiply charged ions is studied using the merged-beams technique at the Advanced Light Source. An ion beam is created using a compact 10-GHz all-permanent-magnet ECR ion source and is accelerated with a small accelerator. The ion beam is merged with a photon beam from an undulator to allow interaction over an extended path. Absolute photoionization cross sections have been measured for a variety of ions along both isoelectronic and isonuclear sequences. FIGURE 1. Schematic diagram of ion-photon mergedbeams end station.
First Observation of Photoelectron Spectra Emitted in the Photoionization of a
The first measurement of photoelectron spectra emitted in the photoionization of a singly charged-ion beam by synchrotron radiation is reported. A Ca -ion beam is resonantly photoionized by the monochromatized photon beam of the SU6 undulator of the SuperACO Storage Ring at 33.20 eV photon energy. The values observed for the kinetic energy and for the intensity of the photoelectron line are in good agreement with the predicted values. The success of this feasibility experiment opens up wide opportunities for similar photoionization and Auger studies on multiply charged ions.
Physical Review A, 2003
Cross sections for the photoionization ͑PI͒ of Sc 2ϩ ions with ͓Ar͔3d ground-state configuration have been measured by employing the merged ion-photon beams method. The Sc 2ϩ ions were produced from metallic vapor in an electron cyclotron resonance ion source, and the photon beam was generated by an undulator in the electron-synchrotron storage ring of the advanced light source of the Lawrence Berkeley National Laboratory. The experimental photon energy range 23-68 eV encompasses the direct 3d and 3p photoionization thresholds. The experimental photoion spectrum is dominated by autoionizing resonances due to 3p excitations predominantly decaying via Coster-Kronig and super-Coster-Kronig transitions. Individual resonances located around EϷ40.2 eV have been measured with an instrumental energy spread ⌬E as low as 1.2 meV, corresponding to a resolving power of E/(⌬E) around 33 500. The fractions of metastable ions in the Sc 2ϩ ion beam are obtained by comparing the photoionization cross section with the recently measured ͓Schippers et al., Phys. Rev. A 65, 042723 ͑2002͔͒ cross section for the time-reversed process of photorecombination of Sc 3ϩ ions. Absolute strengths of several 3p 5 3d 2 and 3p 5 3d 4s PI resonances have been determined. They are the same as the corresponding resonance strengths for isoelectronic Ca ϩ ions.
Physical review letters, 2015
Single, double, and triple ionization of C^{1+} ions by single photons is investigated in the energy range of 286-326 eV, i.e., in the range from the lowest-energy K-vacancy resonances to well beyond the K-shell ionization threshold. Clear signatures of C^{1+}(1s2s^{2}2p^{2} ^{2}D,^{2}P) resonances are found in the triple-ionization channel. The only possible mechanism producing C^{4+}(1s^{2}) via these resonances is direct triple-Auger decay, i.e., a four-electron process with simultaneous emission of three electrons.
Absolute measurements of photoionization cross-sections for ions
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2005
A merged-beam setup for absolute measurements of photoionization cross-sections of ions is described. The facility is capable of recording cross-sections as low as 10 À19 cm 2 and has been used to study a large number of singly-and multiply-charged, atomic and molecular, positive and negative ions. It is based on a synchrotron radiation beam line fitted with an undulator at the storage ring ASTRID and a low-energy ($2 keV) ion beam line. Photons in the energy range 15-200 eV are merged co-linearly with the target ions over a distance of 50 cm, and the absolute photoionization cross-section is determined from the resulting photoion yield with a typical accuracy of 10%. Different types of ion sources are available, thus permitting a large number of positive and negative, atomic and molecular, singly-and multiply-charged ions to be investigated. Emphasis is put on accurate determination of the absolute cross-sections, requiring calibration of photodiode and particle detectors together with measurements of the photon-ion overlap.