A model that allows interpretation of positron annihilation spectra (LT and CDB) in nanodispersed dielectric powders is developed. Model takes into account e+ capture by vacancy-type defects, formation of e+ surface-bound states, as well as the formation of quasi-free positronium (inside crystallites) which may escape into intergranular space where it becomes thermalized during elastic collisions. The process of annihilation of ortho-Ps is narrowed down to its conversion into the para-state as a result of collisions with oxygen molecules (O2) adsorbed on the surface of crystallites. A computer program for lifetime spectra fitting that accounts on the parameters of the above model is developed (with ROOT framework). Combination of the program with our CDB software allows joint processing of the LT and CDB annihilation spectra of nanopowders.

Topics
Computer programming, Crystallographic defects, Exotic atoms, Nanomaterials, Elastic collisions
1.
C.
 
Dauwe
,
T.
 
Van Hoecke
,
D.
 
Segers
 “
Positronium Physics in fine powders of insulating oxidesx
”,
Proceedings of XXX Zakopane School of Physics “Condensed Matter Studies by Nuclear Methods
”, Eds.
K.
 
Tomala
 and
E.A.
 
Gorlich
,
Zakopane, Poland
, 6-13.05.
1995
Google Scholar
 
2.
B.
 
Van Waeyenberge
,
C.
 
Dauwe
 “
The interaction of positronium with paramagnetic surface defect at low temperatures in fine Al2O3 powders
”,
Radiation Physics and Chemistry
, V.
68
, pp.
553
–
556
(
2003
) doi:
https://doi.org/10.1016/S0969-806X(03)00229-9
Google Scholar
Crossref
Search ADS
 
3.
P.S.
 
Stepanov
,
S.V.
 
Stepanov
,
V.M.
 
Byakov
,
F.A.
 
Selim
 “
Developing New Routine for Processing Two-Dimensional Coincidence Doppler Energy Spectra and Evaluation of Electron Subsystem Properties in Metals
”
Acta Physica Polonica A
, Vol.
132
(
5
), pp.
1628
–
1633
(
2017
) doi:
https://doi.org/10.12693/APhysPolA.132.1628
Google Scholar
Crossref
Search ADS
 
4.
P.S.
 
Stepanov
,
F.
 
Selim
,
S.V.
 
Stepanov
,
V.M.
 
Byakov
 “
Positron and Positronium in Al2O3 nanopowders
” Paper in this issue.
5.
Table of Integrals, Series, and Products. Eighth edition.
I.S.
 
Gradshtein
 and
I.M.
 
Ryzhik
.
Ed. D.
 
Zwillinger
.
Elsevier Inc.
,
Amsterdam
,
2015
. ISBN 978-0-12-384933-5
6.
K.
 
Sudarshan
,
D.
 
Dutta
,
S.K.
 
Sharma
,
A.
 
Goswami
.
P.K.
 
Pujari
 “
Air quenching of positronium in meso-porous materials: positron porosimetry
”
J. Phys.: Condens. Matter
Vol.
19
,
386204
(
2007
) doi:
https://doi.org/10.1088/0953-8984/19/38/386204
Google Scholar
Crossref
Search ADS
 
This content is only available via PDF.
© 2019 Author(s).
2019
Author(s)