chemical physics of discharges - Argonne National Laboratory

i'
I
Y
'
493
..
10E.G ~r,~-l {i;ig. 6) , and freshly ;,rc,,ar'cd asi'i~alecl-ic-iodine cosplexes in
CSz also csiiibited an enhanccmcnr in absorprion 'in the regiofi of lOC0 to
11 jO cn-1, w:IicIi is generally ascl-iilcu to complex iormation.
Tile x-ray spectrograms in rile region 20 = 2 - 42" of the asphaltene'
(mi)-iodine 'systca yielded in aiiior;),ious pattern with broad halos as shown
. .
in Xg. 7. For samples with an iodinc content of less tian 5 per cent,
the j. ji band.stil1 appeared as ii siioulder.
was fornad at a;oound 8.7a.
In thc meantime a new band
AT bigher'iodine conhenis (>IO$), the 3.5i
band. has apparently disappeared and the 8.7x band became clearly visible.
".
liisrc is a general overall decrease of total intensity as $1 increases
since the iodine itself absorbs an increasingly large fraction of the
.. .
diffracted x-rays. In the present case, the noise Level coupled with the
intensity reduction has made the disappearance of the 3.51 shoulder dif-
ficult KO detect.
In gcnera1,the . . ESR,spectra obtained froqthe asphaltene-iodine
samples indicated an incre,ase in free radical concentration with increase
-in iodine content. The increase in relacive intensity for an asphaltene
(Wj-iodine complex ,.containing 2@ I over the corresponding native asphal-
. .
tenes is about 3.8 fold.
DISCUSSIOX'
In all the samples studied, including both.native asphalcenes
and their iodine. adducts, a negative temperature coefficient of resistivity
was obtained.
by the plots shown.in Fig. 2:
The linearity of log D vs. reciprocal T .is substantiated
The resistivity is inversely related to
the concentration of the charge carriers (holes and electrons), but the
fact that the number of charge-carriers increases exponentially with tempera-
ture does not enable a choice to be made between electronic or ionic conduction
"