1,720,976 research outputs found
Atomic orientation driven by broadly-frequency-modulated radiation: Theory and experiment
No full textWe investigate magnetic resonances driven in thermal vapor of alkali-metal atoms by laser radiation broadly modulated at a frequency resonant with the Zeeman splitting. A model accounting for both hyperfine and Zeeman pumping is developed, and its results are compared with experimental measurements performed at relatively weak pump irradiance. The interplay between the two pumping processes generates intriguing interaction conditions, often overlooked by simplified models
Spurious ferromagnetic remanence detected by hybrid magnetometer
No full textNuclear magnetic resonance detection in ultra-low-field regime enables the measurement of different components of a spurious remanence in the polymeric material constituting the sample container. A differential atomic magnetometer detects simultaneously the static field generated by the container and the time-dependent signal from the precessing nuclei. The nuclear precession responds with frequency shifts and decay rate variations to the container magnetization. Two components of the latter act independently on the atomic sensor and on the nuclear sample. A model of the measured signal allows a detailed interpretation on the basis of the interaction geometry. Published under license by AIP Publishing
Studying and applying magnetic dressing with a Bell and Bloom magnetometer
Full text linkThe magnetic dressing phenomenon occurs when spins precessing in a static field (holding field) are subjected to an additional strong alternating field. It is usually studied when such extra field is homogeneous and oscillates in one direction. We study the dynamics of spins under dressing condition in two unusual configurations. In the first instance, an inhomogeneous dressing field produces a space-dependent dressing phenomenon, which helps to operate the magnetometer in a strongly inhomogeneous static field. In the second instance, besides the usual configuration with a static and a strong orthogonal oscillating magnetic fields, we add a secondary oscillating field, which is perpendicular to both. The system shows novel and interesting features that are accurately explained and modelled theoretically. Possible applications of these novel features are briefly discussed
A physical model for the characterization of magnetic hydrogels subject to external magnetic fields
No full textMagnetic hydrogels are interesting nanomaterials able to change their shape and temperature if exposed to external magnetic fields. Thanks to these features, which originate from the microstructure of magnetic hydrogels (magnetic nanoparticles tied together through polymeric chains), these substances have several applications in technological fields and biomedicine. Hydrogels are able to absorb and release large amounts of water, which makes them eligible materials for drug delivery. This feature is made even more attractive in cases where the delivery/release can be externally controlled. Controlling the system using external magnetic fields requires keystone processes like modeling and simulation. In this paper, the properties of the system have been analyzed using a 2D microscopical simulation of a suitable physical model. Experimentally, the behavior of the system with and without the application of external magnetic fields and its dissipative effects have been characterized. Specifically, we analyze the change of size and temperature of an hydrogel system as a function of the external magnetic field frequency, thus providing a fundamental tool for developing magnetic substances suitable for specific applications
Electromagnetic induction imaging: Signal detection based on tuned-dressed optical magnetometry
Full text linkA recently introduced tuning-dressed scheme makes a Bell and Bloom magnetometer suited to detect weak variations of a radio-frequency (RF) magnetic field. We envisage the application of such innovative detection scheme as an alternative (or rather as a complement) to RF atomic magnetometers in electromagnetic-induction-imaging apparatuses
A new class of sum rules for products of Bessel functions
No full textWe derive a new class of sum rules for products of Bessel functions of the first
kind. Using standard algebraic manipulations we extend some of the well known properties of Jn . Some physical applications of the results are also discussed. A comparison with the Newberger [B. S. Newberger, J. Math. Phys. 52, 1278 (1982)] sum rules is performed on a typical example
Computer modeling of frequency-modulation spectra of coherent dark resonances
No full textDynamics of a three-level quantum system in Λ-cofiguration driven by a resonant laser field with and without frequency modulation (FM) is studied for the first time in detail using two simulation techniques - the density matrix and quantum trajectories analysis. This analysis was applied to the FM-spectroscopy of coherent dark resonances in Cs atoms and computer simulation results for the absorption spectra are in qualitative agreement with those taken in an experiment. A graph is presented. Mechanism of forming the dark resonances for the case of the Λ-system interacting with the frequency-modulated laser field. © 2006 by Astro Ltd. Published exclusively by Wiley-VCH Verlag GmbH & Co. KGaA
Method and device for measurement of magnetic induction
No full textThe invention relates to an optical method and device for measurement of magnetic induction of small magnetic fields and small changes in magnetic fields of the order of ~ [mu]Gauss to ~ 10 Gauss based on Coherent Resonances at the Zeeman sublevels of a single hyperfine transition in alkali atoms. The atomic system is coherently excited by means of a laser source with a modulation of the light frequency with a frequency lower than 1 GHz. The modulation frequency at which the Coherent Resonances are registered is a measure of the induction of the existing magnetic field
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
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