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Spectrum and structure of the O−3 and O−4 anions isolated in an argon matrix
Volume 14. nrlmber 4
CfiEhiKAL
PHYSICS LETTERS
SBECTRUM AND STRUCTWRE OF THE 0; ,AND 0; ANIONS ISOLATED IN AN ARGON hL4TRIX ME. JACOX and D.E. MILLIGAN 1V3fi~)rlui 13lrrcciro)‘Stamiariis. Ic’asitD~,~torl il. C. -70,734,
The interaction of electrons with oxygen is 0T especial interest because of the irnportnnce of O- and 0, in the reactions characteristic oT the D region of the ionosphere. A reaction scheme has recently been proposed f I J in wI~ich 0’ and 0; undergo rhrcc-body reactions with 0, to form 05 and 0;. which in turn react to produce;1 variety of anions. 3‘1~ species 0 _, Oi, and 0; were readily identified in studies of the mobi-
iities of negative ions in oxygen [2], Recent work has aIso estabiished the presence of 0;: first detected mass spectrometricaliy by Conway and Nesbitr [3 j. McKnight [4j detected 0, in ~ilnult~l~~us measurements of drift velocity and reaciion rates of negative ions in osygen. Since the drift velocity of 0; ws nearly equal to that of O_, the failure to obtnir~ clear evidence for 0; in the earlier drift selociry studies was understandable. The studies of Psrkes [5] and McKnighr and Swim [6;l also supported rhe near eqmlity of the drift veiocities of the two species and, in addition, provided rate constants for the three-body reaction of C, with O2 and for the reverse decomposition of 0, * ,upon collision with 0,. We have recently demonstrated that electrons prodwed by rhc photoionizrition of alkali metal atoms interact with N,O in solid argon, leading to the pro-
duction of 0‘ [7]. The reactions of the 0’ anion with N20 and with NO to produce N20i and NOi were afso studied. In the following discussion, studies of the reaction of 0‘ with 07_ are reported. The experimentat techniques have been described 5is
liS.4
in the extier report [7f. Ar:O,:N,O - mole ratios of 250: 1: I, 500: 1: 1, 500: I : 2, and 500: 1: 5 were ern-
ployed. Supplemerxary ducted
using
Ar:02
experiments
were also con-
= 100 and 350
samples and an
Ar:Oj 2 200 slunple. As sllown in the solid trace of fig. la, a prominent pair of abscrptions :it WI and 1001 m-i” wx present in initial deposits of Ar:02fNn sar~+cs. These absorptions were previously observed by &drcws f8j ) together with relatively weak absorptiuns at lower frequencies which were not detectable in the srna.llcr sample deposits of the present experiments. As shown in the dotted trace of fig. 1s: upon exposure of the sample to the full ligh
Volume
14, number 4
CHEMICAL PHYSICS LETT’ERS a sixth qucncy.
pair
15 June 1972
of absorptions
Separations
at a somewhat
lower
frc-
of 4 or 5 cm -I were characteristic
psir. indicating that the splitting is conrributed by the trapping of the molecule in different types of of xch
- ---
site in the matrix. In a study of‘ an kr:O?: 15N20 i K sample, the absorptions near SO0 cm-l were identical to those characteristic ot’Ar:07: ‘4N,O + I; studies. These isotopic studies. to hc considered in detail in 9 forthcoming paper [9], arc consistent with the assignment of the absorption near 800 cm-1 to B species containing three osygcn atoms and no r:itrogen ;Itums. The absence of nirrogen from the molcculc is conFirmed by the appearance of a very prominent absorption near 800 cm“ in studies of an Ar:O, + K sample. An earlier study [lo] IUS d crnonstrated that SO; is
(b)
_____-_ -._
,_--4
b ’
:
formed
by the charge-rransfer
interaction
bctwc;n
SO,
and alkali metal
atoms in iHl argon matrix. Such chargetransfer inrerxtion should occur even more readily between O3 and alkali metals. since the cicctron affinity 01’0~ is at least 1.96 eV 11 1j. considerably Sreatcr than that of SO,. Further support for the stabilization of 0; has been provided by the observation of a band
[ 10%
I
I
I
I
I
800
900
1000
cm-
I
system
Fig. 1. (a) Ar:02 posited
\yith
Na
= 250 + Na. 14’K. at
736
-+
l°C
over
period
79.3 pM 02 cod+ of‘ ;?!3
min.
------
sample 3ftCr 150 mir. irradiation by full light of :. mudiumpressure mercury arc. 55.6 $4 O2 ( (b) Ar:02:N20 = 5OO:l:j f Na. IS’fi. ~ 775 PM N20 codeposited with Na at 238 2 !“C over period ot 393 min. ----Same sample after 14-I min irradiation by full light of a medium-pressure mcrcur>’ xc.
Sanlc
at SO2 and 806
cm-l. In the earlier Ar:N20 + M a weak peak sometimes appeared near 800 cm-l. The results of the experiment of fig. I b strongly indicate that traces ot’ oxygen in the sample led to the appearance of this absorption. A Lveak product absorption near 1040 cm’l may be contributed by ozone. Even at a peak optical density ot‘0.39 for the SO’2-cn~-1 absorption, no other product absorptions were detected. In studies of an Ar:-16 07: N 7 IsO + Ns sample, there appeared on mercury-arc photo!@ not on!y the 802%.X-cm-l pair of absorption% but also two other pairs of absorptions at lower frequencies. Irradiation of an 160 + Na sample Icd to the apAr:O, (55/ou ‘“0):~~ peared
studies
pearance of these same three pairs of absorption% plus two additional pairs: and irradiation of an Ar:Oz (55% %): N, 180 + Na sample also led to the appearance of
between
5 100
anit
3700
A, with
vibration31
of approximately 820 cniel, upon mercuryarc irradiation ot‘ Ar:O, :N,O + Na sm~p!cs. Solomon and cowortiers [I’?] have observed ;I b;md m&ximunl near 4500 /7 with similar vibrstional spxings for various inorganic ozonides disso!ved in liquid ammonia. The only previous infrared study of inorganic ozonides was that of Herman and Gigukre [ l3], who at tributed a very prominent SOO-C~-~ absorption and weaker absorptions at 1140 and 1260 cm-* to anion vibrations in ammonium ozonide. Their assignment of the SOO-cm-l peak to ZJ, indicated that the O-O bonds 0fOj were stronger t&t those of03. in Contras1 to the predictions of molecular orbital theory [ iG]. Since the ratio of the 800~cm‘* Prcquency to that of v3 of 0, is closely similar to the ratio of the v3 :lbsorption 0t‘SOj [ 101 to that ofsS02, the reassignment of the EOO-cm-’ absorption to v3 of Oj merits consideration. With this reassignment. four of the pairs of abSOrptiO!iS which may bc assigned IO the oxygen-isotopic species of0; with Czv symmetry can be fitted within cxpcrimental error for a valence angle of 110 -+ 5’. The il”sitions of the observed absorptions of the two asymmetrically substituted niolecules are tilso in satisfactory accord with the values calculated for the v3 fundamental assuming 3 valence angle of I 10’ and using the spacings
least-squares
force
constant
adjustment
program
of
[ I5 1.
Schachtschneidcr
has been observed near SO0 cm_1 on An absorption irradiation of Ar:O,:NIO samples codcposited with Li. Na, K, Or Cs atoms. However, the position and contour of this absorption
arc slightly
dcpcndent
on the alkali
metal. A similar dcpcndcncc has also been noted for the vibrational fundamentals of’s05 [ IO]. The appearance of absorptions of both ‘“0 I60 1602nd I60
I80
160-,
3s well 3s of 160.:
in the Ar: 1602:
N-, IsO + Na study
suggests that pho
experiments.
Two
peaks
appcxed
at 091
and at 1001 cm-l in the sodium-atom studies. Since pltrallcl isotopic shifts were &served for these peaks by Andrews [Y]. they probably resu!t from the sanzc molecule trapped in two different sites in the matrix. As shown in fig. i. these peaks disappeared quite reudilt when the s21nplc ~3s subjected to the full light ol‘;1 mcdiunl-presstire mercury arc. In the I-7oIassiurn-Ll.tolli expcrinients. a single prominent peak appeared at 993
This peak has previously been reported by Andrews /I61 in studies of the Ar:O> + K system and has been assigned to ;1 species of formula KO,. Since the oxygen-isotopic pa:tern possessed only six peaks and required the presence of two distinct O2 groups in the molecule, ;1n O,KO, structure was proposed. In the present experiments. prolonged mercury-arc irradiatioa of samples containing potassium atoms Iid to relatively little decrease in this 9934~1” absorption, in contrast to the results in the sodium-ntom studies. E:
xnd the presence
incompletely
characterized
type
of chcnkal
bonding.
The recently
of two distinct
O2 groups
in the mol-
ecule. However, in order for the metal atom to occupy a central position. it is necessary to postulate 3 new,
demonstrated occurrence of0; in the gas phase [3-61 rcopcns the possibility thst an Xl’...Oj species with the cation in 3 peripheral position might be stabilized in the nzatris. Tht’ dcpcndence of the position of the absorption on the nature of the alkali metal provides no barrier to such a reassignment; similar small cation perturbations I~YJCalso been observed for NOi [7j, SOi [lo], and 02, for which there is no reasonable possibility of embedding the cation within the anion structure. Assignment of the absorption to with an 0; fundlimental of an ion pair is also consistent the fr;i!ure to observe an absorption due to LiO, 2nd with the increasing photolytic stability of the hi04 species in going from sodium to ccsium. Chargc-transfer interaction should occur least readily for lithium atoms and most readily for cesium atoms. Hence, LiO, should be the last ionic ot‘the X10, species and the least likely to undergo a reaction of’the type hl+ . . . 0,
+ 0,
+ Xlf . . . 0;
~
with 0, trapped in a11 adjacent site in the argon lattice. This reaction is analogous to th e gas-phclse reaction by which 0; is known to be formed. Among the possible alternate structures is one in which state 0, between
the incompletely and 0,
overlap
filled
TP orbitnls
to form
;1 weak
of ground(P-T”‘)
u bond
the two O2 units. This type of bonding has been considered by Spratley and I’imentel 1171. The remaining unpaired electron of 0; would be delocalized in a plane perpendicular to that of the new bond, resulring in two cquivnlcnt 0, groups. Conway [ 151 has performed semi-empirical molecular orbital calc~llations for the planar 0; ion-molecule complex and has estimated that the mos! stable structure is of trur2s-configuration. Sillce there are ten possible osygen-isotopic species of rr~s-O,l but only siu osygen-isotopic absorptions have been observed, several of the oxygen-isotopic absorptions of the rrarrs-structure must be superposed. To test this possibility, the structure proposed by Conway [ I Sj and the seven frequencies for which a d?finite assignment was possible were fitted to a twoconstant valence-force potential [ 151, and the resulting potcniial constants were used to calculate the frequencies of the remaining isotopic absorptions. The
results are summarized in table 1. The absorptions of
Volume
14, number
Comparison
4
of obscrvcd
---
CHEMICAL
TJblC 1 a) 2nd calcuiatcd for rrarxi); -----
Specks ‘60 ‘60 lb0 ‘60.
ObSW&i
Calclllatcd
1 Ml. 0
I 003.9
180
160
160
160.
987.
160
180
lGo
bo-
957.5
160
160
180
ISo-
160 180 IY,? Iflo_ ‘“0 I60 I60 “O-
970. 0 ( 974.5) ( 974.5)
‘60
‘“0
Itio
ISo-
( 974,
160
180
1x0
ISO-
IS0 IGo ‘“0 IHO IYO ‘“0
HO.
lug_
b) absorptions
959.5 959.5 917.5
:
92s.
PHYSICS
(cm- i)
s
987.0
5)
967. s 975.5 975.5 475.5
959. 7 95% 3 946.1
15 June
JLTTI3RS
1972
coupling constant the 4culatd frecpcncies of the two I6 0, IsO- species would approach each other, in accord with the observations, while the three absorptions of thu ( I60 !SO)5 species should remain supcrposed. It is con&l&d that a trolls-0; structure with 9 central (p-z*‘) (J bond can satisfxtorily explain all of the presently available infrared data for M’Oj. withOilt tllC llCCd to pOStl_ll;itC 2 IlCiV tYpC Of lllCt2l-OSy$!ll bonding. References
D313 t’or Cs+ 0:. V:ilucs in p;~rcn:hescs not used in ICastfit. 1)) ~-O’o” = (4.75 z 0.01) x ICI’ N111-' ;rnd ko"()" = (2.11) :c 0.65) x IO’ Km-l. f’or rro?wo--0”-o”-o’SIrUctUrC
a)
sqn:~rcs
given
by Conway
[IS].
L.(;.
Mckrnipht, I’hss. Rev. A 2 (1970) 763. Parks. ‘Trilns. F;lrad;ly SOC. G 7 ( 197 1) 7 1 I. L.C;. hlcKni$t and J.31. Saxvina. Phys. Rcu. A 4 f 1971) 1043. D.1;. Milligan and 1l.E. Jawx. J. Chum. Phys. 55 ( I97 I) 3404. L. Andwvs, J. I’hys. C!:cm. 73 (1969) 3922. D.A.
the three (IGO *sO); _ species are calculated to appear at the same _frequency, only 1.O and1 from the prominent peak which was not used in the Icast-squares tit. In view oi‘ the severe approsinutions. the agreement is quite reasonable. The extent of deviation of the calculated from LIE actual structural parameters is unhOWi1. Al th0ugll the bending froquencics of a weakly bound chain structure arc N&y t3 be 19x-y low. arid the bending tSorcc constants correspondingly small. i-or
heavy-lirom chains they 3rc’ not completely
non-iqli-
gible. The observed spread bctwcen the tibsorption of ‘CO4 and that oflSO; esceeds the calculated spread by 4 WI - 1. Inclusion of the low-frequency bending fundamental of the same syrnrnctry in ihe calculation would reduce this deviation, as would an appreciable anhnrmonic contribution to the vibration. The estimated value of the coupling force constant between the two ko”O”. 0, groups, is surprisingly large for a11 O...O bond distance ;IS great as 2.08 A. For ;1 srnallcr value of this
3I.E. Jacox and D.I-. %lilligan, Spcctry. D.E. Mill&m 2nd >l.I<. Jaw\.
co bc submitted J. Chem.
Phys.
to J. nlul. 55 (1971)
! 003. J. 13crkmvitz. W.A. Chupka and D. Gntman. J. Chcm. Pliys. 55 (1971) 2733. I.J. Solomon. K. Iluttori.
A.J. J. Am.
Kacmarek. Chcm.
J.M. McDonau~h
Sm.
32. (1960)
and
5640.
and PA. Giy;‘re. Can. J. Chcm. 43 (1965) 1746. AD. W;1lsh. J. Chcni. SW. [ 1953) X66. J.H. Schachtsvhncitiu, Tech. Rept. Nos. 73 1-64 antI 57-65 (Shell Development Co.. ilmcryville. Calif., 1964) arid private communic;ltion. Ii. Herman
L. Andwvs, J. Chem. Phys. $4 ( 1971) 4935. R.D. SpratIcy ( 1966) 2391. D.C. Coli\vay,
and (;.C.
Pirucntcl,
1. Am. Chcm.
J. Chcm.
Ph!l~. 50 (1969)
3864.
SW. 88
CfiEhiKAL
PHYSICS LETTERS
SBECTRUM AND STRUCTWRE OF THE 0; ,AND 0; ANIONS ISOLATED IN AN ARGON hL4TRIX ME. JACOX and D.E. MILLIGAN 1V3fi~)rlui 13lrrcciro)‘Stamiariis. Ic’asitD~,~torl il. C. -70,734,
The interaction of electrons with oxygen is 0T especial interest because of the irnportnnce of O- and 0, in the reactions characteristic oT the D region of the ionosphere. A reaction scheme has recently been proposed f I J in wI~ich 0’ and 0; undergo rhrcc-body reactions with 0, to form 05 and 0;. which in turn react to produce;1 variety of anions. 3‘1~ species 0 _, Oi, and 0; were readily identified in studies of the mobi-
iities of negative ions in oxygen [2], Recent work has aIso estabiished the presence of 0;: first detected mass spectrometricaliy by Conway and Nesbitr [3 j. McKnight [4j detected 0, in ~ilnult~l~~us measurements of drift velocity and reaciion rates of negative ions in osygen. Since the drift velocity of 0; ws nearly equal to that of O_, the failure to obtnir~ clear evidence for 0; in the earlier drift selociry studies was understandable. The studies of Psrkes [5] and McKnighr and Swim [6;l also supported rhe near eqmlity of the drift veiocities of the two species and, in addition, provided rate constants for the three-body reaction of C, with O2 and for the reverse decomposition of 0, * ,upon collision with 0,. We have recently demonstrated that electrons prodwed by rhc photoionizrition of alkali metal atoms interact with N,O in solid argon, leading to the pro-
duction of 0‘ [7]. The reactions of the 0’ anion with N20 and with NO to produce N20i and NOi were afso studied. In the following discussion, studies of the reaction of 0‘ with 07_ are reported. The experimentat techniques have been described 5is
liS.4
in the extier report [7f. Ar:O,:N,O - mole ratios of 250: 1: I, 500: 1: 1, 500: I : 2, and 500: 1: 5 were ern-
ployed. Supplemerxary ducted
using
Ar:02
experiments
were also con-
= 100 and 350
samples and an
Ar:Oj 2 200 slunple. As sllown in the solid trace of fig. la, a prominent pair of abscrptions :it WI and 1001 m-i” wx present in initial deposits of Ar:02fNn sar~+cs. These absorptions were previously observed by &drcws f8j ) together with relatively weak absorptiuns at lower frequencies which were not detectable in the srna.llcr sample deposits of the present experiments. As shown in the dotted trace of fig. 1s: upon exposure of the sample to the full ligh
Volume
14, number 4
CHEMICAL PHYSICS LETT’ERS a sixth qucncy.
pair
15 June 1972
of absorptions
Separations
at a somewhat
lower
frc-
of 4 or 5 cm -I were characteristic
psir. indicating that the splitting is conrributed by the trapping of the molecule in different types of of xch
- ---
site in the matrix. In a study of‘ an kr:O?: 15N20 i K sample, the absorptions near SO0 cm-l were identical to those characteristic ot’Ar:07: ‘4N,O + I; studies. These isotopic studies. to hc considered in detail in 9 forthcoming paper [9], arc consistent with the assignment of the absorption near 800 cm-1 to B species containing three osygcn atoms and no r:itrogen ;Itums. The absence of nirrogen from the molcculc is conFirmed by the appearance of a very prominent absorption near 800 cm“ in studies of an Ar:O, + K sample. An earlier study [lo] IUS d crnonstrated that SO; is
(b)
_____-_ -._
,_--4
b ’
:
formed
by the charge-rransfer
interaction
bctwc;n
SO,
and alkali metal
atoms in iHl argon matrix. Such chargetransfer inrerxtion should occur even more readily between O3 and alkali metals. since the cicctron affinity 01’0~ is at least 1.96 eV 11 1j. considerably Sreatcr than that of SO,. Further support for the stabilization of 0; has been provided by the observation of a band
[ 10%
I
I
I
I
I
800
900
1000
cm-
I
system
Fig. 1. (a) Ar:02 posited
\yith
Na
= 250 + Na. 14’K. at
736
-+
l°C
over
period
79.3 pM 02 cod+ of‘ ;?!3
min.
------
sample 3ftCr 150 mir. irradiation by full light of :. mudiumpressure mercury arc. 55.6 $4 O2 ( (b) Ar:02:N20 = 5OO:l:j f Na. IS’fi. ~ 775 PM N20 codeposited with Na at 238 2 !“C over period ot 393 min. ----Same sample after 14-I min irradiation by full light of a medium-pressure mcrcur>’ xc.
Sanlc
at SO2 and 806
cm-l. In the earlier Ar:N20 + M a weak peak sometimes appeared near 800 cm-l. The results of the experiment of fig. I b strongly indicate that traces ot’ oxygen in the sample led to the appearance of this absorption. A Lveak product absorption near 1040 cm’l may be contributed by ozone. Even at a peak optical density ot‘0.39 for the SO’2-cn~-1 absorption, no other product absorptions were detected. In studies of an Ar:-16 07: N 7 IsO + Ns sample, there appeared on mercury-arc photo!@ not on!y the 802%.X-cm-l pair of absorption% but also two other pairs of absorptions at lower frequencies. Irradiation of an 160 + Na sample Icd to the apAr:O, (55/ou ‘“0):~~ peared
studies
pearance of these same three pairs of absorption% plus two additional pairs: and irradiation of an Ar:Oz (55% %): N, 180 + Na sample also led to the appearance of
between
5 100
anit
3700
A, with
vibration31
of approximately 820 cniel, upon mercuryarc irradiation ot‘ Ar:O, :N,O + Na sm~p!cs. Solomon and cowortiers [I’?] have observed ;I b;md m&ximunl near 4500 /7 with similar vibrstional spxings for various inorganic ozonides disso!ved in liquid ammonia. The only previous infrared study of inorganic ozonides was that of Herman and Gigukre [ l3], who at tributed a very prominent SOO-C~-~ absorption and weaker absorptions at 1140 and 1260 cm-* to anion vibrations in ammonium ozonide. Their assignment of the SOO-cm-l peak to ZJ, indicated that the O-O bonds 0fOj were stronger t&t those of03. in Contras1 to the predictions of molecular orbital theory [ iG]. Since the ratio of the 800~cm‘* Prcquency to that of v3 of 0, is closely similar to the ratio of the v3 :lbsorption 0t‘SOj [ 101 to that ofsS02, the reassignment of the EOO-cm-’ absorption to v3 of Oj merits consideration. With this reassignment. four of the pairs of abSOrptiO!iS which may bc assigned IO the oxygen-isotopic species of0; with Czv symmetry can be fitted within cxpcrimental error for a valence angle of 110 -+ 5’. The il”sitions of the observed absorptions of the two asymmetrically substituted niolecules are tilso in satisfactory accord with the values calculated for the v3 fundamental assuming 3 valence angle of I 10’ and using the spacings
least-squares
force
constant
adjustment
program
of
[ I5 1.
Schachtschneidcr
has been observed near SO0 cm_1 on An absorption irradiation of Ar:O,:NIO samples codcposited with Li. Na, K, Or Cs atoms. However, the position and contour of this absorption
arc slightly
dcpcndent
on the alkali
metal. A similar dcpcndcncc has also been noted for the vibrational fundamentals of’s05 [ IO]. The appearance of absorptions of both ‘“0 I60 1602nd I60
I80
160-,
3s well 3s of 160.:
in the Ar: 1602:
N-, IsO + Na study
suggests that pho
experiments.
Two
peaks
appcxed
at 091
and at 1001 cm-l in the sodium-atom studies. Since pltrallcl isotopic shifts were &served for these peaks by Andrews [Y]. they probably resu!t from the sanzc molecule trapped in two different sites in the matrix. As shown in fig. i. these peaks disappeared quite reudilt when the s21nplc ~3s subjected to the full light ol‘;1 mcdiunl-presstire mercury arc. In the I-7oIassiurn-Ll.tolli expcrinients. a single prominent peak appeared at 993
This peak has previously been reported by Andrews /I61 in studies of the Ar:O> + K system and has been assigned to ;1 species of formula KO,. Since the oxygen-isotopic pa:tern possessed only six peaks and required the presence of two distinct O2 groups in the molecule, ;1n O,KO, structure was proposed. In the present experiments. prolonged mercury-arc irradiatioa of samples containing potassium atoms Iid to relatively little decrease in this 9934~1” absorption, in contrast to the results in the sodium-ntom studies. E:
xnd the presence
incompletely
characterized
type
of chcnkal
bonding.
The recently
of two distinct
O2 groups
in the mol-
ecule. However, in order for the metal atom to occupy a central position. it is necessary to postulate 3 new,
demonstrated occurrence of0; in the gas phase [3-61 rcopcns the possibility thst an Xl’...Oj species with the cation in 3 peripheral position might be stabilized in the nzatris. Tht’ dcpcndence of the position of the absorption on the nature of the alkali metal provides no barrier to such a reassignment; similar small cation perturbations I~YJCalso been observed for NOi [7j, SOi [lo], and 02, for which there is no reasonable possibility of embedding the cation within the anion structure. Assignment of the absorption to with an 0; fundlimental of an ion pair is also consistent the fr;i!ure to observe an absorption due to LiO, 2nd with the increasing photolytic stability of the hi04 species in going from sodium to ccsium. Chargc-transfer interaction should occur least readily for lithium atoms and most readily for cesium atoms. Hence, LiO, should be the last ionic ot‘the X10, species and the least likely to undergo a reaction of’the type hl+ . . . 0,
+ 0,
+ Xlf . . . 0;
~
with 0, trapped in a11 adjacent site in the argon lattice. This reaction is analogous to th e gas-phclse reaction by which 0; is known to be formed. Among the possible alternate structures is one in which state 0, between
the incompletely and 0,
overlap
filled
TP orbitnls
to form
;1 weak
of ground(P-T”‘)
u bond
the two O2 units. This type of bonding has been considered by Spratley and I’imentel 1171. The remaining unpaired electron of 0; would be delocalized in a plane perpendicular to that of the new bond, resulring in two cquivnlcnt 0, groups. Conway [ 151 has performed semi-empirical molecular orbital calc~llations for the planar 0; ion-molecule complex and has estimated that the mos! stable structure is of trur2s-configuration. Sillce there are ten possible osygen-isotopic species of rr~s-O,l but only siu osygen-isotopic absorptions have been observed, several of the oxygen-isotopic absorptions of the rrarrs-structure must be superposed. To test this possibility, the structure proposed by Conway [ I Sj and the seven frequencies for which a d?finite assignment was possible were fitted to a twoconstant valence-force potential [ 151, and the resulting potcniial constants were used to calculate the frequencies of the remaining isotopic absorptions. The
results are summarized in table 1. The absorptions of
Volume
14, number
Comparison
4
of obscrvcd
---
CHEMICAL
TJblC 1 a) 2nd calcuiatcd for rrarxi); -----
Specks ‘60 ‘60 lb0 ‘60.
ObSW&i
Calclllatcd
1 Ml. 0
I 003.9
180
160
160
160.
987.
160
180
lGo
bo-
957.5
160
160
180
ISo-
160 180 IY,? Iflo_ ‘“0 I60 I60 “O-
970. 0 ( 974.5) ( 974.5)
‘60
‘“0
Itio
ISo-
( 974,
160
180
1x0
ISO-
IS0 IGo ‘“0 IHO IYO ‘“0
HO.
lug_
b) absorptions
959.5 959.5 917.5
:
92s.
PHYSICS
(cm- i)
s
987.0
5)
967. s 975.5 975.5 475.5
959. 7 95% 3 946.1
15 June
JLTTI3RS
1972
coupling constant the 4culatd frecpcncies of the two I6 0, IsO- species would approach each other, in accord with the observations, while the three absorptions of thu ( I60 !SO)5 species should remain supcrposed. It is con&l&d that a trolls-0; structure with 9 central (p-z*‘) (J bond can satisfxtorily explain all of the presently available infrared data for M’Oj. withOilt tllC llCCd to pOStl_ll;itC 2 IlCiV tYpC Of lllCt2l-OSy$!ll bonding. References
D313 t’or Cs+ 0:. V:ilucs in p;~rcn:hescs not used in ICastfit. 1)) ~-O’o” = (4.75 z 0.01) x ICI’ N111-' ;rnd ko"()" = (2.11) :c 0.65) x IO’ Km-l. f’or rro?wo--0”-o”-o’SIrUctUrC
a)
sqn:~rcs
given
by Conway
[IS].
L.(;.
Mckrnipht, I’hss. Rev. A 2 (1970) 763. Parks. ‘Trilns. F;lrad;ly SOC. G 7 ( 197 1) 7 1 I. L.C;. hlcKni$t and J.31. Saxvina. Phys. Rcu. A 4 f 1971) 1043. D.1;. Milligan and 1l.E. Jawx. J. Chum. Phys. 55 ( I97 I) 3404. L. Andwvs, J. I’hys. C!:cm. 73 (1969) 3922. D.A.
the three (IGO *sO); _ species are calculated to appear at the same _frequency, only 1.O and1 from the prominent peak which was not used in the Icast-squares tit. In view oi‘ the severe approsinutions. the agreement is quite reasonable. The extent of deviation of the calculated from LIE actual structural parameters is unhOWi1. Al th0ugll the bending froquencics of a weakly bound chain structure arc N&y t3 be 19x-y low. arid the bending tSorcc constants correspondingly small. i-or
heavy-lirom chains they 3rc’ not completely
non-iqli-
gible. The observed spread bctwcen the tibsorption of ‘CO4 and that oflSO; esceeds the calculated spread by 4 WI - 1. Inclusion of the low-frequency bending fundamental of the same syrnrnctry in ihe calculation would reduce this deviation, as would an appreciable anhnrmonic contribution to the vibration. The estimated value of the coupling force constant between the two ko”O”. 0, groups, is surprisingly large for a11 O...O bond distance ;IS great as 2.08 A. For ;1 srnallcr value of this
3I.E. Jacox and D.I-. %lilligan, Spcctry. D.E. Mill&m 2nd >l.I<. Jaw\.
co bc submitted J. Chem.
Phys.
to J. nlul. 55 (1971)
! 003. J. 13crkmvitz. W.A. Chupka and D. Gntman. J. Chcm. Pliys. 55 (1971) 2733. I.J. Solomon. K. Iluttori.
A.J. J. Am.
Kacmarek. Chcm.
J.M. McDonau~h
Sm.
32. (1960)
and
5640.
and PA. Giy;‘re. Can. J. Chcm. 43 (1965) 1746. AD. W;1lsh. J. Chcni. SW. [ 1953) X66. J.H. Schachtsvhncitiu, Tech. Rept. Nos. 73 1-64 antI 57-65 (Shell Development Co.. ilmcryville. Calif., 1964) arid private communic;ltion. Ii. Herman
L. Andwvs, J. Chem. Phys. $4 ( 1971) 4935. R.D. SpratIcy ( 1966) 2391. D.C. Coli\vay,
and (;.C.
Pirucntcl,
1. Am. Chcm.
J. Chcm.
Ph!l~. 50 (1969)
3864.
SW. 88