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Sökning: WFRF:(Chamma M. A.)

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1.
  • Houde, M., et al. (författare)
  • The generation and transformation of polarization signals in molecular lines through collective anisotropic resonant scattering
  • 2022
  • Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 511:1, s. 295-315
  • Tidskriftsartikel (refereegranskat)abstract
    • We discuss the existence of elliptical polarization in rotational spectral lines of CO and other molecules within the context of the Anisotropic Resonant Scattering (ARS) model. We show that the effect of ARS on the radiation field can lead to not only the previously predicted transformation of background linear polarization into circular polarization (i.e. Faraday conversion) but also the occurrence of Faraday rotation and the generation of elliptically polarized signals in an otherwise initially unpolarized radiation field. This is due to a collective behaviour between the large number of molecules acting as a diffraction ensemble that strongly favours forward scattering over any other mode. Our application to astronomical data demonstrates the dependency of the Stokes parameters on the strength and orientation of the ambient magnetic field, and suggests that ARS will manifest itself for a wide range of molecular species and transitions.
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2.
  • Wyenberg, C. M., et al. (författare)
  • Generalization of the Menegozzi and Lamb maser algorithm to the transient superradiance regime
  • 2021
  • Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 507:3, s. 4464-4480
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigate the application of the conventional quasi-steady state maser modelling algorithm of Menegozzi & Lamb (ML) to the high field transient regime of the one-dimensional Maxwell-Bloch (MB) equations for a velocity distribution of atoms or molecules. We quantify the performance of a first order perturbation approximation available within the ML framework when modelling regions of increasing electric field strength, and we show that the ML algorithm is unable to accurately describe the key transient features of R. H. Dicke's superradiance (SR). We extend the existing approximation to one of variable fidelity, and we derive a generalization of the ML algorithm convergent in the transient SR regime by performing an integration on the MB equations prior to their Fourier representation. We obtain a manifestly unique integral Fourier representation of the MB equations which is $\mathcal {O}\left(N\right)$ complex in the number of velocity channels N and which is capable of simulating transient SR processes at varying degrees of fidelity. As a proof of operation, we demonstrate our algorithm's accuracy against reference time domain simulations of the MB equations for transient SR responses to the sudden inversion of a sample possessing a velocity distribution of moderate width. We investigate the performance of our algorithm at varying degrees of approximation fidelity, and we prescribe fidelity requirements for future work simulating SR processes across wider velocity distributions.
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  • Resultat 1-2 av 2
Typ av publikation
tidskriftsartikel (2)
Typ av innehåll
refereegranskat (2)
Författare/redaktör
Lankhaar, Boy, 1991 (2)
Rajabi, F. (2)
Chamma, M. A. (2)
Johnstone, D. (1)
Houde, M. (1)
Wyenberg, C. M. (1)
Lärosäte
Chalmers tekniska högskola (2)
Språk
Engelska (2)
Forskningsämne (UKÄ/SCB)
Naturvetenskap (2)

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