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Proučavanje atomskih prijelaza numerovom metodom u shematskom modelu
Get PDFThe calculation of a partial cross section in atomic collision theory when the collision is inelastic and there is not a possibility of particle exchange requires the solution of a system of coupled differential equations. The Numerov technique is applied to the solution of schematic model equations, which simulate the solution of real problems but are themselves exactly solvable. We have investigated the 32S transition in sodium as an excellent application of a near resonance and strong coupling situation in the case of two-state approximation. The results are compared with those obtained by the Bethe and resonance distortion approximations. The difference can be ascribed to the use of the set of two-channel differential equations rather than the set of three-channel equations used in other approximations, and to the simplified treatment of the interaction potentials.Računanje parcijalnih udarnih presjeka u teoriji atomskih sudara, kad je sudar neelastičan i nema izmjene čestica, zahtijeva rješavanje sustava vezanih diferencijalnih jednadžbi. Primjenjujemo Numerovu metodu za rješavanje shematskog sustava jednadžbi koje oponašaju rješenje stvarnih problema, a se mogu egzaktno riješiti. Proučavamo 32S prijelaz u natriju kao odličnu primjenu uvjeta blizu rezonancije i snažnog vezanja za slučaj približenja razmatranjem dva stanja. Ishodi računa uspoređuju se s ishodima Betheovog približenja i približnog računa ometanja rezonancije. Razlika se može pripisati primjeni dvokanalnih diferencijalnih jednadžbi umjesto trokanalnih jednadžbi u drugim približenjima i pojednostavljenim razmatranjem potencijala međudjelovanja
Proučavanje atomskih prijelaza numerovom metodom u shematskom modelu
Get PDFThe calculation of a partial cross section in atomic collision theory when the collision is inelastic and there is not a possibility of particle exchange requires the solution of a system of coupled differential equations. The Numerov technique is applied to the solution of schematic model equations, which simulate the solution of real problems but are themselves exactly solvable. We have investigated the 32S transition in sodium as an excellent application of a near resonance and strong coupling situation in the case of two-state approximation. The results are compared with those obtained by the Bethe and resonance distortion approximations. The difference can be ascribed to the use of the set of two-channel differential equations rather than the set of three-channel equations used in other approximations, and to the simplified treatment of the interaction potentials.Računanje parcijalnih udarnih presjeka u teoriji atomskih sudara, kad je sudar neelastičan i nema izmjene čestica, zahtijeva rješavanje sustava vezanih diferencijalnih jednadžbi. Primjenjujemo Numerovu metodu za rješavanje shematskog sustava jednadžbi koje oponašaju rješenje stvarnih problema, a se mogu egzaktno riješiti. Proučavamo 32S prijelaz u natriju kao odličnu primjenu uvjeta blizu rezonancije i snažnog vezanja za slučaj približenja razmatranjem dva stanja. Ishodi računa uspoređuju se s ishodima Betheovog približenja i približnog računa ometanja rezonancije. Razlika se može pripisati primjeni dvokanalnih diferencijalnih jednadžbi umjesto trokanalnih jednadžbi u drugim približenjima i pojednostavljenim razmatranjem potencijala međudjelovanja
Entanglement dynamics of bipartite system in
No full textEntanglement plays a crucial role in quantum information protocols, thus
the dynamical behavior of entangled states is of a great importance. In this paper we
suggest a useful scheme that permits a direct measure of entanglement in a two-qubit
cavity system. It is realized in the cavity-QED technology utilizing atoms as flying
qubits. To quantify entanglement we use the concurrence. We derive the conditions,
which assure that the state remains entangled in spite of the interaction with the
reservoir. The phenomenon of sudden death entanglement (ESD) in a bipartite system
subjected to squeezed vacuum reservoir is examined. We show that the sudden death
time of the entangled states depends on the initial preparation of the entangled state
and the parameters of the squeezed vacuum reservoir
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Atom trapping and dynamics in the interaction of optical vortices with quadrupole-active transitions
Get PDFRecent studies have confirmed the coupling of optical vortices, such as Laguerre-Gaussian and Bessel-Gaussian modes, to quadrupole-active atomic transitions. This interaction has been shown to be enhanced considerably in the case of Laguerre-Gaussian beams due to the gradient coupling, particularly, in the case of a relatively large winding number. Here, we consider the trapping and the dynamics of atoms in the optical quadrupole potential generated by two coaxial counterpropagating optical vortex beams. We focus on the atomic transition 62S1/2→52D5/2 in Cs which is a dipole-forbidden but a quadrupole-allowed transition. We show how this atomic transition engages with the optical vortex fields at near resonance, leading to atom trapping in the optical quadrupole potential well accompanied by translational motion. We show how the optical forces generate the motion of the atoms trapped within the quadrupole potential, illustrating the results using typical experimentally accessible parameters
Quadrupole absorption rate and orbital angular momentum transfer for atoms in optical vortices
Get PDFRecent experiments involving the interaction of optical vortices with atoms in quadrupole transitions have shown it to be accompanied by the exchange of orbital angular momentum (OAM) between the electronic states of the atom and the optical vortex field. Earlier work, both theoretical and experimental, had ruled out the transfer of a vortex OAM to the electronic degrees of freedom in an electric dipole atomic transition and it has been confirmed that the lowest multipolar order involving an OAM transfer to the electronic motion is indeed the electric quadrupole. Hitherto, the quadrupole transition involving optical vortices has not been quantified and we thus set out to evaluate the absorption rate accompanied by an OAM transfer with reference to the [EQUATION] in Cs when cesium atoms are subject to the field of a linearly polarized optical vortex. Our results assuming typical experimentally accessible parameters indicate that the absorption rate for moderate light intensities is lower than the quadrupole spontaneous emission rate but should still be within the measurement capabilities of modern spectroscopic techniques
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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