ELFT HÍRADÓ

["Dr. KAJCSOS, Zsolt" <kajcsos AT rmki.kfki.hu>]

CMRC SZEMINÁRIUM


Prof. Tomas Goworek

Marie Curie-Sklodowska University, Lublin, Poland


"Applicability and elaboration of the Tao-Eldrup  model for Ps-trapping: 
the case of porous
substances"
The most popular application of the positron annihilation spectroscopy is 
the determination of the size of small free spaces in the structure of 
solids. The analysis of positron lifetime spectra gives
two quantities related to free volumes: the ortho-positronium lifetime and 
the probability of its formation (intensity of long-lived component). The 
meaning of ortho-Ps intensity I3 will be briefly decsribed.
During the last 20 years, the relation positron lifetime - void size was 
used mainly in the structure investigations of polymers, containing voids 
in the subnanometer range. The equation for the ortho-Ps decay rate, given 
by Tao and Eldrup, fits well to that range. However, an extension of the 
model toward larger voids (e.g. mesopores) request to take into account the 
location of Ps on higher
excited levels of a particle in the potential well. Such an extension of 
the Tao-Eldrup model will be presented and its limitations discussed.

2003. október 30-án, csütörtökön 10 órakor
az RMKI Tanácsteremben (III. ép. II. em.)




> 1121 Budapest, Konkoly-Thege u. 29-33.
> Szervezi: Kajcsos Zsolt, KFKI RMKI, 
> kajcsos AT rmki.kfki.hu