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تصفح المحتوي RDA
التصفح حسب الموضوعات
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التصفح حسب تاريخ النشر
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تصفح الهيئات
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التصفح حسب نوع المادة
التصفح حسب العلاقة بالعمل
تم العثور علي : 44
 تم العثور علي : 44
  
 
إعادة البحث

Book 2013.
ISBN: 978-0-495-38569-1

Articles 2021.
Vol. 60, No. 2 (April 2021) /

Articles 2019
(2019, vol. 163(September /
   

Articles 2020.
Vol. 59, No. 5 (October 2020) /

Thesis 2016
This thesis is devoted to calculation the energy eigenvalues of the channeled positrons through single wall carbon nanotubes (n - m). According to the continuum model approximation given by Lindhard for the case of an axial channeling in single crystals - the actual periodic potential of a row of atoms is replaced by a potential averaged over a direction parallel to the row - called continuum potential. The calculations were executed by using the atomic interaction potential as given by Moliere potential and Biersack’s universal potential. The maximum number of bound states and the energy eigenvalues were calculated for positrons of 100 MeV energy incident in a direction parallel to the nanotube axis - by using WKB method. The calculations showed that the estimation of the maximum number of bound states of the channeled positron in armchair - chiral - and zigzag nanotubes is higher for the Moliere potential than for the Universal potential. The calculations showed that the effect of temperature by using Debye approximation of thermal vibration amplitude on the channeling potential is very small and gave the same eigenvalues and the same number of bound states as that for the static nanotubes.
Also
- the channeling radiation characteristics of positrons channeled in single-walled carbon nanotubes (SWCNTs) were estimated. The channeled positrons move along the nanotube axis - (z-axis) - with energies (10-500) MeV. This thesis covers SWCNTs with different chiral indices (n - m). The energy eigenvalues - in a plane normal to the nanotube axis (xy-plane) - of relativistic positron channeled through SWCNTs has been used to calculate the emitted photon energy in the forward direction - i.e - channeling radiation. Also - the calculations covered both the wave length of the emitted radiation and the maximum number of bound states of the channeled positrons as a function of the nanotube radius at different incident energies. The results of the calculations showed that - in this energy range - the emitted radiation energy lies in the X-ray band and as the energy of the incident positron increases - the emitted radiation energy increases towards the γ- energy band and accordingly - the wave length decrease towards the γ-band for the same transition . For all values of positron energy - the wave length of the emitted radiation was found to be a decreasing function of the nanotube radius while the maximum number of bound states of the channeled positrons is an increasing function of the nanotube radius for the different types of SWCNTs namely - zigzag - armchair and chiral.

Book [2014] ,©2014
ISBN: 9781470410438 ,1470410435

Book 1983
ISBN: 0387119833

Book 1975
ISBN:

Book 1977
ISBN: 0387071474

Book 1972
ISBN: 0127424504


من 5
 







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