Journal
of
Research
of
the Na tional
Bureau
of
Standa
rds Vol. 57, N
o.4,
October
1956
Re
s
ear
ch
Pa
pe r 2
71
3
Mass
Spectrum of Sulfur
Vapor
Paul
Bradt
,
Fred
1.
Mohler
,
and
Vernon
H.
Dibeler
Th
e
ma
ss sp
ect
rum
of s
ulfur
vapor
ha
s
been
measu
re d
by
evapo
ra
t
in
g sulfur
from
a
heat
ed t ube
dir
ect
ly in
to
t he
ionization
ch
ambe
r of a
ma
ss sp e
ct
r
omet
er. I ons S
;;
with x
ra
ngi ng fro m 1
to
8
are
ob
served
with
St
mo
st
ab
und
ant. I s
otopc
ab
und
anc
es w ere
com-
pu
ted
fr
om
t he S
;-
ions.
Th
e
appearance
p
otent
ials of S:
and
St
are
r
es
pectIv
cl
.v
8.9 ± 0.2
a
nd
8.3 ±0.2 el
ect
ron
volt
s.
Thi
s sugg
est
s t
ha
t t he
vapor
in t he ioni
zat
i
on
chamber
is a
mixture
of
mo
lecul es con
ta
ining S2 and S8
and
po
ss
ib
ly
ot
he r molecules.
1.
Introduction
Th
e
ma
ss spect
rum
of sulfur
vapor
has been
st
udied
in
co
nn
ec
ti
on
with
a prog
ram
to establish reference
sa
mp
l
es
of
natura
l isotopic
abundance
[lV . While
one objective of
this
s
tud
y was to check
th
e Isotope
ratios
and
the chemical puri
ty
of
the
reference sampl
e,
the mass spect
rum
a
nd
the a
pp
ea
ran
ce potentials arc
of research interest.
Th
e molec ular we ight of sulfur
va
por
indicates
that
the
va
por
in
equilibri
um
wi
th
sulfur
at
1750 C is
pr
edominantly S8
[2]
.
Thi
s is a
rel
atively
un
sta
ble
co
nfiguration,
and
in
the
presence
of
an
c'Iectric dischluge
an
S2
band
spect
rum
is
observed
[3].
Th
e vi
bration
series
and
predissocia-
tion spectra. give
wi
th
so
me uncertain
ty
a
va
lue of
4.4 ev for the 82
bond
energy, indi
ca
ting tlla t S2 is
quit
e
sta
bl
e.
2.
Exper
i
mental
Procedure
Th
e sulfur from
the
reference-sample stock is virgin
sulfur from a dome in
vVh
ar
to
n
County,
T
ex.
Th
e
sulfur
-va
por
pr
eSS
Ul'
e is too small to meaSUl'e the
ma
ss
spectr
um
at
room
te
mp
eratl
~r
e
,
a
nd
t.he
meas
urement
s were m
ade
by evaporfl
tmg
the
sulfur
from a h
eated
tube
in
to
the ioniza
Lio
n c
hamb
er of a
60
0
ma
ss
spect
rom
eter. A few
mi
l
li
g
ram
s of coarse
powder were held in a capi
ll
ary
tube
with
a thermo-
co
uple
in
c
onta
ct
with
the tube.
Th
is
in
t
urn
wa
s
in
a 6-mm tube, which e
xt
e
nded
about
2 cm to the
e
ntran
ce
port
of the ionization c
hamb
er.
Th
e ion-
iza tion
cham
ber reac
hed
a
tempernture
of 1860 C
duril
1g
operation
and
the
sample
attained
a
steady
te
mp
erat
ur
e of
94
0 C by h
eat
c
ondu
ct
ion
and
radia
-
tion.
Thi
s
prov
ed to be a convenie
nt
temperature
for recording the
spectr
um. .
Sulfur dioxide was
made
by burning
the
sulfur
111
a,
ir
,
an
d
the
ma
ss spect
rum
of
S0
2
and
the
ail"
oxygen
was measured
with
a 1800 gas-a nalysis
ma
ss spec-
tr
om
eter.
This
is the
co
nventional
method
of meas-
Ul'ing sulfur-isotope abundances.
1 Fig
ur
es
ill
bracket
s intlicat e
th
e lit
cra
tlll'e referen ces at th e end of this pa
pC!'
.
3. Results
3.1 .
Mass
Sp
e
ctrum
Table
1 gives the
prin
cipal ions observed in
the
ma
ss spect
rum
of sulfur
vapo
r. Column 3 giv
es
the
re
lativ
e
abu
ndance of th e ions
S
~2,
whereas
co
lumn
4
gives th e m onoisotopic s
pertrum.
It
is the s
um
. of
th
e isotope peaks
in
each Sx group rel
ative
to
the
S2
ions
taken
as 100.
Th
e
rather
compli
cated
isotope
st
ru
cture
iden ti
fies
all these ions as predominan
tly
singly c
har
ged ions, except for th e
fo
llowi
ng.:
l\1ass 16
from S
++
was 0.05 percen t of tl
te
64
peak m a spec-
trum
where 0 + from O2 a
nd
CO2 wa s negligible.
~la
ss
32}
~
from S
32
83
3++
was 0.06
percent
of th e 64
peak, ancl is abou t 4 percen t of the
65
peak.
Hen
c
e,
doubly charged ions of mass
64
co
ntribut
e 4 percent
to the
32
pea
k.
A
peak
at
ma
ss 80 from S
t+
is
0.06 percent of the
64
peal
\:.
Impuriti
es
th
at
ca n be ascribed to the sulfur
]'
atl~
e
r
than
the
ma
ss-spectrometer
backg
r
ound
arc vo latIle
gase
s,
which decrease wit,h time. H2S+
ranged
from.
1.2 to
0.1
5 percent of the
64
peak, and
Cs
t
WfiS
0.13
Lo
0.07 percent. A 48
peak
rangi ng from 0.17
to
0.02
pOl'
ce
nt
m
a
~
T
be
80+ from S0 2.
'
l
~he
molec:ule
ion
masked
by St would be a
bou
t
LW
lce
the
SO+
peak.
l'
ABLE
1. J
lr
ass sp
ec/n
l1
n oj
su
lfu
r vapor
m
le
Ion
32
______________ S
32
64
___
___________
S
~2
96 _
___
__________ S
32
3
128
___
__________ S
:'
160 _____________
S
~'
192 _____________
S
~'
224 _____________
S
~'
256 ____________ _
S
~2
Relati ve
int
ens
it
y
1:3.
5
100. 0
4. 7
8. 1
5. 2
3.
2
O. 3:3
5.
.
J.
Monoi
so-
topi
c s pec-
trL1m
12. 8
100. 0
5.
0
9.
0
6.
1
3. 9
O. 43
7. 3
223
