Extreme ultraviolet emission lines of Ca XV in solar and laboratory spectra

New R-matrix calculations of electron impact excitation rates in Ca XV are used to derive theoretical electron density diagnostic emission line intensity ratios involving 2s(2)2p(2)- 2s2p(3) transitions, specifically R-1 = I(208.70 Angstrom)/I(200.98 Angstrom), R-2 = I(181.91 Angstrom)/I(200.98 Angstrom), and R-3 = I(215.38 Angstrom)/I(200.98 Angstrom), for a range of electron temperatures (T-e = 10(6.4)-10(6.8) K) and densities (Ne = 10(9)-10(13) cm(-3)) appropriate to solar coronal plasmas. Electron densities deduced from the observed values of R-1, R-2, and R-3 for several solar flares, measured from spectra obtained with the Naval Research Laboratory's S082A spectrograph on board Skylab, are found to be consistent. In addition, the derived electron densities are in excellent agreement with those determined from line ratios in Ca XVI, which is formed at a similar electron temperature to Ca XV. These results provide some experimental verification for the accuracy of the line ratio calculations, and hence the atomic data on which they are based. A set of eight theoretical Ca XV line ratios involving 2s(2)2p(2)-2s2p(3) transitions in the wavelength range similar to140-216 Angstrom are also found to be in good agreement with those measured from spectra of the TEXT tokamak plasma, for which the electron temperature and density have been independently determined. This provides additional support for the accuracy of the theoretical line ratios and atomic data.

Excitation rates for transitions in Ca XV

Collision strengths for transitions among the energetically lowest 46 fine-structure levels belonging to the (1s(2)) 2s(2)2p(2), 2s2p(3), 2p(4), and 2s(2)2p3l configurations of Ca XV are computed, over a wide electron energy range below 300 Ryd, using the Dirac Atomic R-matrix Code (DARC) of Norrington & Grant (2003). Resonances in the threshold region have been resolved in a fine energy mesh, and excitation rates are determined over a wide electron temperature range below 10(7) K. The results are compared with those available in the literature, and the accuracy of the data is assessed.

Effective collision strengths for transitions in Fe XV

Collision strengths for transitions among the energetically lowest 53 fine-structure levels belonging to the (1s(2)2s(2)2p(6)) 3l(2), 3l3l', 3s4l and 3p4s configurations of Fe XV are computed, over an electron energy range below 160 Ryd, using the Dirac Atomic R-matrix Code (DARC) of Norrington & Grant (2003). Effective collision strengths, obtained after integrating the collision strengths over a Maxwellian distribution of electron energies, have also been calculated. These results of effective collision strengths are tabulated for all 1378 inelastic transitions over a wide temperature range of 10(5) to 10(7) K. Comparisons are also made with other R-matrix calculations and the accuracy of the results is assessed.

Effective collision strengths for transitions among the 3s(2), 3s3p and 3p(2) configurations of Fe xv

Effective collision strengths for transitions among the ten energetically lowest fine-structure levels belonging to the (1s(2)2s(2)2p(6))3s(2), 3s3p and 3p(2) configurations of Fe xv have been calculated in the electron temperature range of 10(5)-10(7) K, using the recent Dirac atomic R-matrix code of Norrington and Grant. The results are compared with the other recently available independent Breit-Pauli R-matrix calculations of Eissner et al (Eissner W, Galavis M E, Mendoza C and Zeippen C J 1999 Astron. Astrophys. Suppl. 137 165) and Griffin et al (Griffin DC, Badnell N R, Pindzola M S and Shaw J A 1999 J. Phys. B: At. Mol. Opt. Phys. 32 2139, 4129). Large differences are observed for many transitions over almost the entire temperature range. These differences are analysed and discussed, and the accuracy of the calculations is assessed.

Energy levels and radiative rates for transitions in Ar XIII, Ar XIV and Ar XV

Energies for 524 levels of Ar XIII, 460 levels of Ar XIV and 156 levels of Ar XV have been calculated using the GRASP code of Dyall et al. (1989). Additionally, radiative rates, oscillator strengths, and line strengths are calculated for all electric dipole (E1), magnetic dipole (M1), electric quadrupole (E2), and magnetic quadrupole (M2) transitions among these levels. Comparisons are made with the limited results available in the literature, and the accuracy of the data is assessed. Our energy levels are estimated to be accurate to better than 1%, whereas results for other parameters are probably accurate to better than 20%. Additionally, the level lifetimes derived from our radiative rates are in excellent agreement with measured values.

Inner-shell photoexcitation of Fe XV and Fe XVI

The configuration-interaction method as implemented in the computer code CIV3 is used to determine energy levels, electric dipole radiative transition wavelengths, oscillator strengths and transition probabilities for inner-shell excitation of transitions in Fe XV and Fe XVI. Specifically, transitions are considered of the type 1s(2) 2s(2) 2p(6) 3s(2) -1s(2) 2s(2) 2p(5) 3l3l' 3l" (l, l' and l" = s,p or d) in FeXV and 1s(2) 2s(2) 2p(6) 3s- 1s(2) 2s(2) 2p(5) 3l3l' (l and l' = s,p or d) in FeXVI, using the relativistic Breit-Pauli approach. An assessment of the accuracy of the derived atomic data is performed.

An investigation of Fe XV emission lines in solar flare spectra

Previously, large discrepancies have been found between theory and observation for Fe XV emission line ratios in solar flare spectra covering the 224-327 angstrom wavelength range, obtained by the Naval Research Laboratory's S082A instrument on board Skylab. These discrepancies have been attributed to either errors in the adopted atomic data or the presence of additional atomic processes not included in the modelling, such as fluorescence. However our analysis of these plus other S082A flare observations (the latter containing Fe XV transitions between 321-482 angstrom), performed using the most recent Fe XV atomic physics calculations in conjunction with a chianti synthetic flare spectrum, indicate that blending of the lines is primarily responsible for the discrepancies. As a result, most Fe XV lines cannot be employed as electron density diagnostics for solar flares, at least at the spectral resolution of S082A and similar instruments (i.e.similar to 0.1 angstrom). An exception is the intensity ratio I(3s3p P-3(2)-3p(2) P-3(1))/I(3s3p P-3(2)-3p(2) D-1(2))=I(321.8 angstrom)/I(327.0 angstrom), which appears to provide good estimates of the electron density at this spectral resolution.

Inventing the Origin of Theatre History: The Modern Uses of Juba II's 'teatriké historia'

La contabilità come mezzo per diffondere i valori religiosi. Il caso della diocesi di Ferrara del XV secolo.

Il tema del ruolo della contabilità nella Chiesa, con particolare riferimento al legame esistente tra contabilità e valori religiosi, non appare ad oggi sufficientemente studiato, soprattutto se si considera l’importanza economica e sociale di tale istituzione nel passato e nel presente. Il lavoro intende contribuire a tale indagine analizzando la realtà della Diocesi di Ferrara del XV secolo. Il Quattrocento rappresenta per la Chiesa italiana un’epoca di grande importanza, in quanto caratterizzato da un tentativo di riforma promosso da Papa Eugenio IV, volto a combattere la dilagante corruzione morale all’interno del clero e a riportare quest’ultimo alla sua funzione pastorale. L’appello pontificio venne accolto con particolare attenzione da due vescovi ferraresi, Giovanni Tavelli da Tossignano e Francesco Dal Legname, che attraverso le loro visite pastorali cercarono di divulgare i valori della riforma nella propria Diocesi. La promozione della nuova moralità, nell’esperienza ferrarese, era basata anche sulla diffusione degli strumenti contabili, mezzo essenziale per mettere in luce l’operato dei diversi membri del clero ed in particolare l’utilizzo da parte loro dei beni della Chiesa. Attraverso lo studio di documenti originali del XV secolo, scritti in lingua latina, il contributo si propone di mettere in luce come la contabilità possa assumere un ruolo complementare alla promozione dei valori religiosi.