Some Aspects of Positronium Interaction with Elementary Free Volumes in Polymers

V.P. Shantarovich
2001 Acta Physica Polonica. A  
a n t a r o v i c h Seme nov Inst it ute of C hemi cal Ph ysics, Russian A cademy of Sciences 4 K osygin str ., 117334, Mosco w, Russia T his pap er contains a discussion of original and recently pu blished results on positroniu m annihil ati on lif etime studies of elementary free volumes in the group of p olymer glasses. T he results are used for indic atio n of non-homogene ity of these materials and give some basis for considerin g a connection of the long-liv ed comp onent intensities I 3
more » ... nt intensities I 3 ( I 4 ) with concentrations N 3 ( N 4 ) of elementary free volumes and, in this w ay, w ith fractional free volume. PACS numb ers: 78.70.Bj 1. I n t r o d u ct io n T od ay, p osi t ro ni u m anni hi l ati on l i feti m e ( PA L) spectro scopy can b e considered as the m ost di rect pro be m etho d to esti m ate free vol um es i n p ol ym ers. The l on gest l i feti me comp onent(s) § 3 ( § 4 ) , b eing chara cteri sti c o f a nni hi l ati o n i n the b ound sta te e + e À (a hydro gen-li ke o r t ho -p ositro ni um ato m o-Ps) i s i ndi cati ve of free vol ume i n materi al [1{ 4]. La rg e num b er of pa pers are devo ted to thi s pro bl em. W e are no t goi ng to di scuss here the whol e spectrum of the studi es i n thi s Ùel d and ref er the i nterested reader to the b o ok [5] and to som e of the recent publ icati ons of m ore or l ess general chara cter [6{ 8]. In the scop e of the m echani sm of n on-i n stant an eous tra ppi ng of Ps by elementa ry free vol umes ( E FV) [6, 9] , whi ch seems to be supported no w by the recent ang ul ar-m omentum -correl ati on (A M O C) exp eri ments [10], we shal l demonstra te the appro ach to quanti ta ti ve a nal ysi s of P AL exp eri menta l results f or a l arg e num b er of p ol ym er gl asses (T abl e 1, [11] ) wi th di˜erent f ree vo l um es. Our resul ts [11] on o -Ps quenchi ng by O 2 wi tho ut i nhi bi ti on of Ps form ati on i n some p ol ym er gl assesg ive the Ùrst di rect evi dence of no n-hom ogeneit y of these materi al s. Recent di scussion on thi s to pi c by Fu j i i and R i gby i s m enti oned i n [11] . Indi cati on on exi stence of com pl ex size-di stri buti on of free vol um e elements was obta i ned usi ng both Ùnite-term and conti nuo us pro cedures of the da ta trea tm ent. A smo oth tra nsiti on was observed f rom uni m odal to (4 87)
doi:10.12693/aphyspola.99.487 fatcat:vzktrsr2lbemnbu4w4ju4y5mum