Neutral C60 is well known to exhibit a giant resonance in its photon absorption spectrum near 20 eV. This is associated with a surface plasmon, where delocalized electrons oscillate as a whole relative to the ionic cage. Absolute photoionization cross-section measurements for C+60, C2+60, and C3+60 ions in the 17-75 eV energy range show an additional resonance near 40 eV. Time-dependent density functional calculations confirm the collective nature of this feature, which is characterized as a dipole-excited volume plasmon made possible by the special fullerene geometry.

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Lifetimes for K-shell vacancy states in atomic carbon have been determined by measurement of the natural linewidth of the 1s → 2p photoexcited states of C + ions. The K-shell vacancy states produced by photoionization of atomic carbon are identical to those produced by 1s → 2p photoexcitation of a C + ion: 1s2s 2 2p 2 2 D, 2 P, and 2 S autoionizing states occur in both cases. These vacancy states stabilize by emission of an electron to produce C 2+ ions. Measurements are reported for the lifetime of the 1s2s 2 2p 2 2 D, 2 P and 2 S autoionizing states of C + : 6.3 ± 0.9 fs, 11.2 ± 1.1 fs and 5.9 ± 1.3 fs respectively. Knowledge of such lifetimes is important for comparative studies of the lifetimes of Kshell vacancies in carbon-containing molecules, benchmarking theory, and interpreting satellite x-ray spectra from astrophysical sources such as x-ray binaries. Absolute cross sections were measured for both ground-state and metastable-state ions providing a stringent test of state-of-the-art theoretical calculations.Carbon is ubiquitous in nature and is the building block of life. This atom in its various stages of ionization has relatively few electrons, and is thus amenable to theoretical study. Lifetimes

We have investigated L-shell photoionization (PI) of 1S ground-state and 3Po metastable states of the Be-like ion, B+, in the photon energy range 22.4–31.3 eV, at an experimental energy resolution of 25 meV. Absolute PI cross sections have been measured using a photon–ion merged-beams arrangement at the Advanced Light Source. Detailed calculations using the semi-relativistic Breit–Pauli R-matrix approach suggest a fraction of 29% of metastable ions in the primary beam of the experiment. Excellent agreement is observed between the theoretical predictions and the experimental high-resolution PI cross sections. The present results are compared with earlier experimental and theoretical work. The cross section for PI of B+ ground-state ions can be very well described by an analytic formula derived from quantum defect theory.

Absolute cross sections for the K-shell photoionization of C-like nitrogen ions were measured by employing the ion-photon merged-beam technique at the SOLEIL synchrotron radiation facility in Saint-Aubin, France. Highresolution spectroscopy with E/∆E ≈ 7,000 was achieved with the photon energy from 388 to 430 eV scanned with a band pass of 300 meV, and the 399.4 to 402 eV range with 60 meV. Experimental results are compared with theoretical predictions made from the multi-configuration Dirac-Fock (MCDF) and R-matrix methods. The interplay between experiment and theory enabled the identification and characterization of the strong 1s → 2p resonances observed in the spectra.