الفهرس 
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Abstract
ABSTRACT
A mass spec~rome~er of ~he t.ype A~las CH-4 is used in
combinat.ion wit.helect.ron impact. t.echnique in order t.o st.udy
the energelics of production of molecular ions as well as
[ CHaOH] + • [CaHaOl + and [CaHeO] +. fragment.ions produced from
lhree diols namely. 1.2-Et.hanediol [C2HeOa]+’ • 1.3-Propanediol
[C
3
H
8
0a]+’ and 1.4-Bulanediol [C4H100a]+’ The 10n1zation
efficiency CIE) curves for all
t.he ions (except t.he
molecular ion of l,4-Bulanediol) are measured for about. 3.5
eV above t.hreshold and t.reat.edby deconvolut.ed first.differenlial
CDFD) t.echnique
The reIalive inlensilies at. 70 as well as at. 14 eV ~or
t.heprominent. ions in the mass spect.ra of .the t.hree molecules
are measured and discussed . The probable mechanist.ic pat.hways
for t.he formation of t.he prominenl ions oblained from
t.het.hree precursors are also reporled and discussed. The
observed base peak oblained from 1.a-Et.hanediol Ci.e.m/z= 31)
is formed by simple bond cleavage. t.halfrom 1.3-Propanediol
Ci.e.m/z= 58) is formed as a resull of HaO eliminalion by
rearrangement. process whil~ lhe base peak for 1.4-Bulanedlol
Ci.e.m/z= 42) is formed by a secondary decomposilion process.
The values of lonizat.ion energyal lhreshold for 1,2-
Elhanediol and l,3-Propanadiol are measured al 10.22 ± 0.04
and 10.13 ± 0.06 eV .respecli¥ely . The ionizalion energy of
lhe lalt.er molecule is nol published as yet. . However • t.he
ion beam of 1.4-Bulanediol molecular ion is loa weak to measure
with any reasonable accuray . Higher energy levels have
been delected in the ionizalion efficiency (IE) curves of
the molecular ions and some of these levels are tentatively
explained by the author .
The appearance energies CAE’s) of the studied fragment ions
are reported at and near threshold and the different possible
fragmentation processes for the formation of these ions are
discussed It is worthwhile to mention that the AE values of
seven out of nine studied fragment ions are reported for lhe
first lime. Thermodynamical lhreshold CAEth) values for lhese
different processes are calculated for different possible
structural ions • and compared with the experimental AE’s
values . By using appearance energy values together with
thermodynami cal considerat.ions • the author obt.ained some
information about low-energy fragment.ation palhways and the
slructure of lhe studied fragment ions .
The present results may indicate that at threshold m/z= 31
+
fragment ions are formed with (CHZOH) structure. m/z= 43
fragment ions are formed with [CH3CO]+ structure while
m/z= 46
+
fragme~t ions are formed with [CH3CHOH] structure
from the three precursors .
Finally • the calculated heats of formation C~f) of different
ions from experimental AE data are determined and
discussed.