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Dynamics of spontaneous decay and corresponding emission spectrum areexactly treated for a system of two identical two-level atoms in 1D.Just a one-dimensional case is considered in order to maximally extractan information on mutual influence of spatially remote atoms through theradiation field. As a result, an effect is revealed and considered indetail that there exist stable (metastable) entangl
From a detailed elemental abundance analysis of 102 F and G dwarf starswe present abundance trends in the Galactic thin and thick disks for 14elements (O, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Zn, Y, Ba, and Eu).Stellar parameters and elemental abundances (except for Y, Ba and Eu)for 66 of the 102 stars were presented in our previous studies (Bensbyet al. 2003, 2004a). The 36 stars that are new in t
The evolution of the Solar neighbourhood is followed using a unique,magnitude complete and kinematically unbiased sample of 14,000 F, G, andK dwarfs. Metallicity, age, space motion and galactic orbits have beendetermined for all stars. The result is a detailed view of the complexevolution of the local Milky Way, which must be matched by any model forthe chemical and dynamical evolution of the Gala
We present a qualitative physical model of the origin of two very brightUV lines of Fe II at 2507-2509 Å, present in high-resolutionspectra of gaseous condensations (blobs) close to the central star ofeta Carinae. The spectra have been obtained with the Hubble SpaceTelescope (HST). The model is based on a type of Bowen mechanism withselective photoexcitation of Fe II by a broad HLyalpha profile,ge
We show that the Galactic thick disk reaches at least solar metallicities and that it experienced strong chemical enrichment during a period of ~3 Gyr, ending around 8-9 Gyr ago. This finding puts further constraints on the relation and interface between the thin and thick disks and their formation processes. Our results are based on a detailed elemental abundance analysis of 261 kinematically sel
Photoinduced Ba L x-rays were measured, in the excitation energy range of 5.6-30 keV, by using high-brilliance undulator radiation. The obtained intensity ratios, the excitation-energy independent L beta(4)/L beta(3), L eta/L beta(1), L iota/L alpha(1,2), L beta(6)/ L alpha(1,2) and L beta(2,15)/L alpha(1,2) as well as the excitation- energy dependent L beta(1)/L alpha(1,2), L beta(3)/L alpha(1,2)
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We consider possible schemes for the resonance-enhanced two-photon ionization (RETPI) of Ne and Ar atoms under the action of bichromatic radiation of intense resonance lines of HI, HeI, and HeII in a radiation-rich astrophysical plasma. The ionization rate is comparable to or exceeds the recombination rate in rarified astrophysical plasma, which leads to the accumulation of singly ionized ions wit
Previously, weak emission lines had been detected at red wavelengths inthe spectra of a limited sample of mid to late B type main sequencestars. A fuller description of the occurrence and origins of these lineshas yet to be forwarded, in part due to the lack of observationsdetailing the spectral transitions involved. To address this deficiency,we present a line list of weak emission features found
Both the Fe II UV emission in the 2000-3000 Å region [Fe II(UV)]and resonance emission line complex of Mg II at 2800 Å areprominent features in quasar spectra. The observed Fe II(UV)/Mg IIemission ratios have been proposed as means to measure the buildup ofthe Fe abundance relative to that of the alpha-elements C, N, O, Ne,and Mg as a function of redshift. The current observed ratios show largesca
Using a numerical simulation of compressible convection with radiativetransfer mimicking the solar photosphere, we compare the velocity fieldderived from granule motions to the actual velocity field of the plasma.We thus test the idea that granules may be used to trace large-scalevelocity fields at the sun's surface. Our results show that this isindeed the case provided the scale separation is suf
P-mode oscillations in the Sun and stars are excited stochasticly by Reynolds stress and entropy fluctuations produced by convection in their outer envelopes. The excitation increases with increasing effective temperature (until envelope convection ceases in the F stars) and also increases with decreasing gravity.
The enrichment of Fe relative to α-elements such as O and Mgrepresents a potential means to determine the age of quasars and probethe galaxy formation epoch. To explore how Fe II emission in quasars islinked to physical conditions and abundance, we have constructed an 830level Fe II model atom and investigated through photoionizationcalculations how Fe II emission strengths depend on nonabundancef
We present numerical simulations that reproduce the salient features of the amazingly strong [Fe ii andFe ii emission spectra in the B and D Weigelt blobs of Carinae. For our studies we have used spectraobtained during the 1998 epoch observations with the Hubble Space Telescope (HST). The spectrum of the Band D Weigelt blobs dominates in [Fe ii and Fe ii emission lines. The same observations show
We report a strong prepulse dependence of the emission of X-rays from plasmas created by 150 fs Ti:sapphire laser pulses on solids. The laser pulses were focused onto plane samples of aluminium and vanadium with a main pulse power density of about 2.5 x 10(16) W cm(-2). By splitting off a portion of the main pulse we were able to generate a prepulse whose delay and intensity were variable relative
We present and discuss new determinations of metallicity, rotation, age,kinematics, and Galactic orbits for a complete, magnitude-limited, andkinematically unbiased sample of 16 682 nearby F and G dwarf stars. Our∼63 000 new, accurate radial-velocity observations for nearly 13 500stars allow identification of most of the binary stars in the sampleand, together with published uvbyβ photometry, Hipp
