Photoionization of the valence shells of the neutral tungsten atom

Results from large-scale theoretical cross section calculations for the total photoionization of the 4f, 5s, 5p and 6s orbitals of the neutral tungsten atom using the Dirac Coulomb R-matrix approximation (DARC: Dirac-Atomic R-matrix codes) are presented. Comparisons are made with previous theoretical methods and prior experimental measurements. In previous experiments a time-resolved dual laser approach was employed for the photo-absorption of metal vapours and photo-absorption measurements on tungsten in a solid, using synchrotron radiation. The lowest ground state level of neutral tungsten is $\rm 5p^6 5d^4 6s^2 \; {^5}D_{\it J}$, with $\it J$=0, and requires only a single dipole matrix for photoionization. To make a meaningful comparison with existing experimental measurements, we statistically average the large-scale theoretical PI cross sections from the levels associated with the ground state $\rm 5p^6 5d^4 6s^2 \; {^5}D_{\it J}[{\it J}=0,1,2,3,4]$ levels and the \rm 5d^56s \; ^7S_3 excited metastable level. As the experiments have a self-evident metastable component in their ground state measurement, averaging over the initial levels allows for a more consistent and realistic comparison to be made. In the wider context, the absence of many detailed electron-impact excitation (EIE) experiments for tungsten and its multi-charged ion stages allows current photoionization measurements and theory to provide a road-map for future electron-impact excitation, ionization and di-electronic cross section calculations by identifying the dominant resonance structure and features across an energy range of hundreds of eV.Comment: 10 pages, 3 figures, accepted for publication in J Phys B: At. Mol. Opt. Phy

Experiment and theory

Photoionization of neutral atomic sulfur in the ground and metastable states was studied experimentally at a photon energy resolution of 44 meV (full width at half maximum). Relative cross section measurements were recorded by using tunable vacuum ultraviolet radiation in the energy range 9–30 eV obtained from a laser-produced plasma and the atomic species were generated by photolysis of molecular precursors. Photoionization of this atom is characterized by multiple Rydberg series of autoionizing resonances superimposed on a direct photoionization continuum. A wealth of resonance features observed in the experimental spectra are spectroscopically assigned and their energies and quantum defects tabulated. The cross section measurements are compared with state-of-the-art theoretical cross section calculations obtained from the Dirac Coulomb R-matrix method. Resonance series in the spectra are identified and compared, indicating similar features in both the theoretical and experimental spectra

Pneumonia failing to respond to treatment

SummaryHerpes simplex virus type 1 (HSV-1) is frequently isolated from the respiratory tract of critically ill patients. However, diagnosis of clinically significant HSV-1 pneumonia is difficult as the presentation is non-specific and there is no diagnostic reference standard to differentiate from non-infectious contamination.We present a case of HSV-1 pneumonia in a young asthmatic patient who was potentially immunocompromised through long-term corticosteroid usage. The quantitative PCR titre from bronchoalveolar lavage fluid was high (9×103copies/ml) and the patient made a dramatic clinical and radiographic recovery upon treatment with acyclovir. We suggest that similar PCR levels in the appropriate clinical setting should prompt consideration of anti-viral therapy