Search results for "electromagnetic [radiation]"
showing 10 items of 873 documents
Chandra Observation of the Persistent Emission from the Dipping Source XB 1916-053
2006
We present the results of a 50 ks long Chandra observation of the dipping source XB 1916-053. During the observation two X-ray bursts occurred and the dips were not present at each orbital period. From the zero-order image we estimate the precise X-ray coordinates of the source with a 90% uncertainty of 0.6''. In this work we focus on the spectral study of discrete absorption features, during the persistent emission, using the High Energy Transmission Grating Spectrometer on board the Chandra satellite. We detect, for the first time in the 1st-order spectra of XB 1916-053, absorption lines associated to Ne X, Mg XII, Si XIV, and S XVI, and confirm the presence of the Fe XXV and Fe XXVI abso…
A Complex Environment around Circinus X-1
2007
We present the results of an archival 54 ks long Chandra observation of the peculiar source Cir X-1 during the phase passage 0.223-0.261. We focus on the study of detected emission and absorption features using the HETGS. A comparative analysis of X-ray spectra, selected at different flux levels of the source, allows us to distinguish between a very hard state, at a low count rate, and a brighter, softer, highly absorbed spectrum during episodes of flaring activity. The spectrum of the hard state clearly shows emission lines of highly ionized elements, while, during the flaring state, the spectrum also shows strong resonant absorption lines. The most intense and interesting feature in this …
Collective rotation of an oblate nucleus at very high spin
2019
International audience; A sequence of nine almost equidistant quadrupole transitions is observed in Nd137. The sequence represents an extremely regular rotational band that extends to a spin of about 75/2 and an excitation energy of ≈4.5MeV above yrast. Cranked mean-field calculations of the Nilsson-Strutinsky type suggest an oblate shape for the band. They reproduce the observed I(I+1) dependence of the rotational energy whereas predicting a pronounced decrease in the deformation, which is the hallmark of antimagnetic rotation.
The time-harmonic Maxwell equations
1996
In this chapter we shall see that the solution of the time-harmonic Maxwell equations with real coefficients can be transformed to time independent partial differential equations with complex coefficients. Then we introduce a finite element approximation proposed in [Křižek, Neittaanmaki, 1989]. A similar technique is analyzed in [Křižek, Neittaanmaki, 1984b], [Monk, 1992a] (for fully time dependent problems see, e.g., [Monk 1992b,c]).
Maxwell’s Equations
2012
The empirical basis of electrodynamics is defined by Faraday’s law of induction, by Gauss’ law, by the law of Biot and Savart and by the Lorentz force and the principle of universal conservation of electric charge. These laws can be tested – confirmed or falsified – in realistic experiments. The integral form of the laws deals with physical objects that are one-dimensional, two-dimensional, or three-dimensional, that is to say, objects such as linear wires, conducting loops, spatial charge distributions, etc. Thus, the integral form depends, to some extent, on the concrete experimental set-up. To unravel the relationships between seemingly different phenomena, one must switch from the integ…
Theoretical study of the discrete and continuum spectrum of BeH
2008
The transition intensities supplied in this Letter are directly connected with a description of the discrete and continuum spectrum of BeH. An attempt to meet our goal requires the calculation of the absorption oscillator strengths of several transitions to Rydberg states of BeH, together with differential oscillator strengths which give rise to different dipole-allowed photoionization channels from the molecular ground state. The calculations have been performed with the molecular-adapted quantum defect orbital (MQDO) approach. Predictions of new spectroscopic data on BeH at energies where high Rydberg transitions can take place, including the continuum region of the spectrum have been mad…
Total absorption studies of high priority decays for reactor applications: 86Br and 91Rb
2017
Preliminary results from beta decay studies of nuclei that are important for reactor applications are presented. The beta decays have been studied using the total absorption technique (TAS) and the pure beams provided by the JYFLTRAP system at the IGISOL facility of the University of Jyväskylä. peerReviewed
A Theoretical Model for Excitation Energy Transfer in Chlorosomes: Lamellar and Rod-Shaped Antenna Structures
2008
A model based on exciton theory is presented for description of excitation energy transfer in chlorosomes. Three models to describe the internal organization of the pigments inside the chlorosome were considered, a stack of single-wall rods, a stack of double-wall rods and a stack of lamellae directed along the long axis of the chlorosome. Simulated absorption, circular dichroism and linear dichroism spectra of single-wall rod and the lamella structures turned out to be practically identical. It was shown that rod—rod interactions may localize the exciton states in the regions of a rod facing a neighboring rod. Such localized states provide a fast excitation energy transfer mechanism in per…
Exciton description of chlorosome to baseplate excitation energy transfer in filamentous anoxygenic phototrophs and green sulfur bacteria.
2013
A description of intra-chlorosome and from chlorosome to baseplate excitation energy transfer in green sulfur bacteria and in filamentous anoxygenic phototrophs is presented. Various shapes and sizes, single and multiwalled tubes, cylindrical spirals and lamellae of the antenna elements mimicking pigment organization in chlorosomes were generated by using molecular mechanics calculations, and the absorption, LD, and CD spectra of these were predicted by using exciton theory. Calculated absorption and LD spectra were similar for all modeled antenna structures; on the contrary, CD spectra turned out to be sensitive to the size and pigment orientations in the antenna. It was observed that, bri…
Observation of inclined EeV air showers with the radio detector of the Pierre Auger Observatory
2018
With the Auger Engineering Radio Array (AERA) of the Pierre Auger Observatory, we have observed the radio emission from 561 extensive air showers with zenith angles between 60 and 84. In contrast to air showers with more vertical incidence, these inclined air showers illuminate large ground areas of several km2 with radio signals detectable in the 30 to 80 MHz band. A comparison of the measured radio-signal amplitudes with Monte Carlo simulations of a subset of 50 events for which we reconstruct the energy using the Auger surface detector shows agreement within the uncertainties of the current analysis. As expected for forward-beamed radio emission undergoing no significant absorption or sc…