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[en] Photoionization experiments were performed with tungsten ions using a photon-ion merged-beams setup at the Advanced Light Source. Cross-sections σ_q,q+1 for photon-induced single ionization of W^q+ ions (q=1,2,3,5) and σ_q,q+2 for photon-induced double ionization of W⁺ ions have been explored in the energy range 20-70 eV. While σ_q,q+1 for the lower charge states is dominated by broad resonance features in the range of 4f and 5p excitations, the cross-section σ_5,6 shows much narrower peak features. Significant contributions from initial metastable states are evident. Double ionization is substantially enhanced at energies above the threshold for single ionization of a 4f electron in W⁺.

[en] Absolute cross sections for photoionization and electron-impact ionization of Ar⁵⁺ have been measured using two different interacting-beams setups. The spectra consist of measurements of the yield of products due to single ionization as a function of electron or photon energy. In addition, absolute photoionization and electron-impact ionization cross sections were measured to normalize the measured Ar⁶⁺ product-ion yield spectra. In the energy range from 90 to 111 eV, both electron-impact ionization and photoionization of Ar⁵⁺ are dominated by indirect 3s subshell excitation-autoionization. In the energy range from 270 to 285 eV, resonances due to 2p-3d excitation-autoionization are prominent in the photoionization spectrum. In the range from 225 to 335 eV, an enhancement due to 2p-nl (n>2) excitations are evident in the electron-impact ionization cross section. The electron and photon impact data show some features due to excitation of the same intermediate autoionizing states

[en] Relative cross sections for photoionization of W^q+ ions q = 1, ..., 5 were measured at energies up to 90 eV employing the photon-ion merged-beam technique at the Advanced Light Source in Berkeley. While the cross sections for the lower charge states are dominated by broad resonance features in the range of 4f and 5p excitations, the cross section for W⁵⁺ shows much narrower peak features.

[en] Direct mapping of the charge transport efficiency of polymer solar cell devices using a soft X-ray beam induced current (SoXBIC) method is described. By fabricating a polymer solar cell on an x-ray transparent substrate, we demonstrate the ability to map polymer composition and nanoscale structure within an operating solar cell device and to simultaneously measure the local charge transport efficiency via the short-circuit current. A simple model is calculated and compared to experimental SoXBIC data of a PFB:F8BT bulk-heterojunction device in order to gain greater insight into the device operation and physics.

[en] The cross section for photoionization of Xe⁷⁺ has been measured on an absolute scale with the photon-ion merged beams technique at a synchrotron light source. The experimental photon energy range of 95 145 eV comprises the ground state ionization threshold at about 106 eV and the prominent 4d⁹ 5s 5f²P resonance at 122.14 o 0.2 eV. The strength of this resonance is found to account for 15% of the 4d absorption oscillator strength. With an experimental photon energy spread of 50 meV the 4d⁹ 5s 5f²P resonance width could be determined with 8% uncertainty to be 72 meV.

[en] Absolute cross sections were measured for photoionization of Ce^q+ (1 ≤ q ≤ 9) ions at photon energies between 110 eV and 150 eV with a spectral resolution of 0.1 eV. The cross sections in this energy range are dominated by 4d - nf and 4d - np autoionizing transitions. Within the experimental uncertainty, total oscillator strengths for the 4d shell determined by integrating the cross-section measurements are consistent with the sum rule value of 10 based on the number of 4d electrons.

[en] Absolute photoionization cross-section measurements are reported for Se⁺ in the photon energy range 18.0-31.0 eV, which spans the ionization thresholds of the ⁴S_3/2 ground state and the low-lying ²P_3/2,1/2 and ²D_5/2,3/2 metastable states. The measurements were performed using the Advanced Light Source synchrotron radiation facility. Strong photoexcitation-autoionization resonances due to 4p → nd transitions are seen in the cross-section spectrum and identified with a quantum-defect analysis.

[en] Multiple ionization of ions subsequent to absorption of a single photon has been studied employing a photon-ion merged-beam setup at the PETRA III synchrotron radiation facility of DESY in Hamburg. Absolute cross sections for single, double and triple ionization of C"+ ions were measured with emphasis on specific well defined terms of K-shell excited C"+. In particular, the terms C"+ (1s2s"22p"2 "2D,"2P) were excited from the ground level of C"+. Subsequent autoionization processes resulted in the production of C"2"+, C"3"+ and C"4"+ ions. The associated decay mechanisms are single-Auger, double-Auger and triple-Auger decay. The observation of C"4"+ products arising from C"+(1s2s"22p"2 "2D,"2P) unambiguously confirmed the existence of triple-Auger decay, i.e., a process in which 4 electrons interact with one another such that one fills the K-shell vacancy and the others are simultaneously ejected. The experiment yields branching ratios for the Auger decay channels as well as individual decay rates for autoionization and radiative stabilization of the C"+(1s2s"22p"2 "2D,"2P) terms. (paper)

[en] Absolute single photoionization cross-section measurements of Se³⁺ and Se⁵⁺ ions were performed using monochromatized synchrotron radiation and the photo-ion merged-beams technique. Se³⁺ measurements were made at a photon energy resolution of 20 ± 3 meV from 41.90 to 54.56 eV, spanning the ²P_1/2 ground state ionization threshold. Numerous autoionizing resonances arising from both the ²P_1/2 ground state and ²P_3/2 metastable state are identified using quantum defect analysis. For Se⁵⁺, measurements were made at a photon energy resolution of 60 ± 10 meV from 81 to 101 eV, spanning the ²S_1/2 ground state ionization threshold, and at a photon energy resolution of 28 ± 3 meV from 100.175 to 106.675 eV in a region rich with autoionizing resonances. The direct ionization threshold of the Se⁵⁺²S_1/2 ground state is experimentally determined to be 81.780 ± 0.010 eV. (paper)