Unified numerical model of collisional depolarization and broadening rates that are due to hydrogen atom collisions

Created by W.Langdon from gp-bibliography.bib Revision:1.3872

@Article{Derouich:2015:AA,
  author =       "M. Derouich and A. Radi and P. S. Barklem",
  title =        "Unified numerical model of collisional depolarization
                 and broadening rates that are due to hydrogen atom
                 collisions",
  journal =      "Astronomy and Astrophysics",
  year =         "2015",
  volume =       "584",
  month =        dec,
  keywords =     "genetic algorithms, genetic programming",
  oai =          "oai:arXiv.org:1508.06482",
  URL =          "http://arxiv.org/abs/1508.06482",
  URL =          "http://dx.doi.org/10.1051/0004-6361/201526661",
  size =         "8 pages",
  abstract =     "Context. Accounting for partial or complete frequency
                 redistribution when interpreting solar polarization
                 spectra requires data on various collisional processes.
                 Data for depolarization and polarization transfer are
                 needed, but are often lacking, while data for
                 collisional broadening are usually more readily
                 available. Recently it was concluded that despite
                 underlying similarities in the physics of collisional
                 broadening and depolarization processes, the relations
                 between them cannot be derived purely
                 analytically.

                 Aims. We aim to derive accurate numerical relations
                 between the collisional broadening rates and the
                 collisional depolarization and polarization transfer
                 rates that are due to hydrogen atom collisions. These
                 relations would enable accurate and efficient estimates
                 of collisional data for solar applications.

                 Methods. Using earlier results for broadening and
                 depolarization processes based on general (i.e., not
                 specific to a given atom), semi-classical calculations
                 that employ interaction potentials from perturbation
                 theory, we used genetic programming (GP) to fit the
                 available data and generate analytical functions
                 describing the relations between them. The predicted
                 relations from the GP-based model were compared with
                 the original data to estimate the accuracy of the
                 method.

                 Results. We obtain strongly nonlinear relations between
                 the collisional broadening rates and the depolarization
                 and polarization transfer rates. They are shown to
                 reproduce the original data with an accuracy of about
                 5percent. Our results allow determining the
                 depolarization and polarization transfer rates for
                 hyperfine or fine-structure levels of simple and
                 complex atoms. Conclusions. We show that by using a
                 sophisticated numerical approach and a general
                 collision theory, useful relations with sufficient
                 accuracy for applications are possible.",
}

Genetic Programming entries for Moncef Derouich Amr Mohamed Mahmoud Khairat Radi P S Barklem

Citations