1200
The Journal of Physical Chemistty, Vol. 83, No. 9,
Goodman et al.
1979
(18) J. F. Stevens, Jr., P. S.Engel, and R. F. Curl, Jr., paper WM3, Sixth
Austin Symposium on Gas Molecular Structure, Austin, Tex., March
3, 1976.
(19) E. Flood, P. Pulay, and J. E. Boggs, J. Mol. Struct., 50, 355 (1978).
We are grateful to Professor Boggs for making this manuscript
available to us prior to publication.
(20) L. D. Fogel and C. Steel, J . Am. Chem. SOC.,98, 4859 (1976).
(21) S. F. Nelsen, J . Am. Chem. Soc., 96, 5669 (1974).
(22) J. E. Anderson and J. M. Lehn, J. Am. Chem. Soc., 89, 81 (1967).
(23) The vapor pressure data used to estimate the boiling point of
cisdimethyldiizene were not presented in our earlier communication.'0
This data and the procedure used to obtain it are given in the
(24)
(25)
(26)
(27)
Experimental Section of the current paper. The melting point was
done by the Stock method.
W. J. Hehre, J. A. Pople, and A. J. P. Devaquet, J. Am. Ctmm. Soc.,
98, 664 (1976).
The calculated frequencies for the EE and SS conformers were not
identical because two of the interaction constants transferred from
the trans isomer were specific to the NCH bending coordinate for
the in-plane CH bond.
R. N. Camp, I. R. Epstein, and C. Steel, J . Am. Chem. Soc., 99,
2453 (1977).
J. F. Stevens and R. F. Curl, Jr., private communication.
Vibrational Assignments for the Raman and the Phosphorescence Spectra of
9,lO-Anthraquinone and 9,lO-Anthraquinone-d,'
Kevin K. Lehmann,' John Smolarek, Omar S. Khalil,3 and Lionel Goodman*
Department of Chemistty, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08903
(Received November 8, 1978)
The Raman spectra of 9,lO-anthraquinone (AQ) and 9,lO-anthraquinone-d8 are examined. Raman band
assignments are made from this data and from a published normal coordinate analysis. The Raman spectra
of AQ at 5 K is reported and vibrational assignments for the phosphorescence spectra of AQ in n-hexane at
4.2 K are reexamined in light of new 3B1, *A, phosphorescence data. Contrary to previous work from this
laboratory, it is concluded that although higher order vibronic interactions may he operative between the two
closely spaced 3AU-3B1gelectronic states, these interactions are not manifested in the phosphorescence spectra
of AQ in n-hexane at 4.2 K.
-
I. Introduction
9,lO-Anthraquinone (AQ) has become an important
model to study vibronic interactions and possible
breakdown of the Born-Oppenheimer approximation due
to possible interactions between the lowest excited state
(3B1,) with the nearby 3Auand 3Bluelectronic states. The
low temperature, high resolution phosphorescence spectra
of AQ require firm assignment of the vibrational bands in
the ground state.
Vibrational spectra of AQ have been studied using IRG8
and Raman s p e c t r o s ~ o p i e s . ~The
- ~ ~Raman spectra were
obtained on a powder a t room temperature and were
tentatively assigned on the basis of a normal coordinate
analysis (NCA).
In this paper we report a new study of the Raman
spectra of AQ and of its perdeuterated analogue AQ-ds.
Raman data for AQ and AQ-d8 at -300, -100, and -5
K and the normal coordinate analysis are used to assign
the Raman bands. We also report new phosphorescence
data on AQ in n-hexane at 4.2 K. We use the Raman band
assignments and the published IR data to reanalyze the
phosphorescence spectra. The new analysis solves
questionable assignments and some basic questions on
vibronic effects in the phosphorescence spectra of AQ in
n-hexane.
11. Experimental Section
AQ and AQ-ds used in this study were zone refined
under an argon atmosphere. AQ-ds was synthesized by
oxidation of anthra~ene-d,,.'~
Raman spectra were run on a Cary 82 spectrometer
using the Kr+ 6471-w line. Laser power was 100 mV at
the sample. Polarization spectra were run with the Ar+
5145-A line in order to minimize polarized absorption. The
spectral band width was 1 cm-l except for the polarized
-
0022-3654/79/2083-1200$0 1.OO/O
TABLE I: Low F r e q u e n c y R a m a n Spectra ( c m - ' ) of AQ
ref 10
t h i s s t u d y ___
r e f 11
(5K)
83K
RT'
38
36
27 (a,)
30
63
63
51 (a,)
54
65
63
57 ( b g )
60
74
73
66 (a,)
68
83
92
92
82 ( b 1
145
150
148
150
156
a RT denotes r o o m temperature.
(Pg)
spectra which were run with a 3-cm-' band width.
The low solubility of AQ made it impossible to obtain
solution spectra, even by using a saturated solution in
benzene at its boiling point. AQ has a melting point of 285
"C and is stable to 300 "C. However, local heating due to
laser line absorption was enough to cause decomposition
at the melting point. The decomposition product's
fluorescence swamps the Raman spectra.
Raman spectra of AQ and AQ-ds powders at room
temperature at 100 and a t -5 K were obtained using
a capillary tube, a Harney-Miller cell and cold Nz gas, and
an Air Products liquid helium Helitrans cryostat, respectively.
The phosphorescence spectra of AQ in n-hexane at 4.2
K was run as previously described4 except for the excitation source which was the 3371-A line of a Molectron
UV400 pulsed nitrogen laser.
-
11. Results and Discussion
A . Raman Spectra. The low temperature Raman
spectra, 0-160 cm-l at 5 K, are shown in Figure 1. Five
bands are observed below 100 cm-l and two bands are
0 1979 American
Chemical Society
Vlbrational Spectra of Anthraquinone
The Journal of Physical Chemistry, Vol. 83, No. 9, 1979
1201
TABLE 11: Assignments of the Raman Active In-Plane Vibrations (cm-I ) of 9,lO-Anthraquinone
-AQ-h,
AQ-d8
deuteration shift
ag
'12
V11
'10
9'
'R
VI
'6
V5
v 4
v 3
V2
VI
b3,
v33
v32
'31
'30
'29
V28
V21
'26
'2 5
"24
'23
a
obsd"
calcdb
obsd"
calcdb
obsd"
301
47 5
684
1144
1030
1178
1212
1317
1596
1665
3067
307 5
322
50 3
686
1031
1149
1185
1323
1476
1559
1714
3050
3075
289
47 5
645
854
814
1095
(1203)'
(1203)
1569
1660
312
496
685
829
850
1102
1307
1379
1526
1700
2280
2287
12
0
39
290
216
83
9
114
27
35
(250)
364
67 8
924
(1082)
(1308)
(1326)
(1584)
(1653)
3043
3082
27 5
378
705
9 39
1124
1227
1382
1500
1628
3057
3076
234
351
651
901
(830)
27 2
355
67 9
916
85 6
1006
1268
1438
1612
2280
2288
14
13
27
23
252
This work, 5 K powder spectra.
Calculated, ref 12-14.
(1208)
1561
calcd
10
7
1
202
299
83
16
97
33
14
770
788
3
23
26
23
268
22 1
114
62
16
777
818
118
23
' Denotes marginally detected bands.
TABLE 111: Assignments of the Raman Active
Out-of-Plane Vibrations (cm-l ) of 9,lO-Anthraquinone
deuteration
AQ-h,
AQ-di
shift
___--
obsd" calcdb obsda calcdb obsd" calcdb
b,, v 1 6
239
vis
440
v 1 4 770
v , ~ 978?
bzgvzz
vl1
vz0
v19
V I R
vl1
156
419
449
654?
819
990?
232
464
733
939
224
389
609?
220
401
591
808
15
51
161
12
63
142
131
219
409
482
713
847
941
143
410
400
207
408
444
704
639
809
13
9
49
12
1
38
9
208
132
599
" This work, 5 K powder spectra.
I,
220
Calculated ref 12-
14.
IA
150
Flgure 1.
I00
50
Cm-'
Raman spectra of AQ-h, in the 0-150-cm-' region at 5 K.
located a t 150 and 156 cm-'. The data are compared to
that of Miyazaki andl ItolO and of Rasanen and Stenmanll
in Table I
The 148-cm-l line, reported by Ito as having a preferential B, polarization and assigned as a combination of 66
and 82 cm-l, splits into two lines at 150 and 156 cm-' at
5 K. The 66-cm-l line shifts to 74 cm-' while the 82-cm-I
line shifts to 92 cm-l at 5 K. This leads to a frequency sum
of 166 cm-' for this combination thus eliminating that
possibility. Combination of the 60 + 83 cm-l and 68 + 83
cm-' lines, which give good agreement in the room temperature spectra (145 and 150 cm-l), becomes 157 and 166
cm-' at 5 K, hence, also negating them as possible combinations.
Two possible explanations remain. First, these two lines
are combinations of the 63 92 and 65 92 cm-I lines in
the low temperature spectra which gives a good numerical
+
+
agreement with one combination but not the other.
Second, these lines are factor group splitting components
of a molecular vibration. The second possibility was
deemed invalid by Rasanen and Stenmanl' because these
lines are wider than other AQ molecular lines and because
of the observation that the strong lines at 150 cm-' in
naphthaquinone and in anthrone crystals disappear in
solution or in melts.
Our line width measurements at 5 K do not show a
difference between the 150- and 156-cm-l pair and molecular lines. The assignment of these two lines as a lattice
combination is plausible but uncertain. Furthermore the
deuteration shift (9-10 cm-') for these bands is much too
large for lattice modes. The (rn(AQ)/rn(AQ-d8))1/2= 1.02
factor for lattice modes predicts only a 3-cm-' isotope shift.
Hence we assign the 150/156-cm-' pair as a factor group
split molecular band.
The Raman data at higher frequencies agree essentially
with that of Rasanen and Stenman,l' but differ from that
published by Singh and Singh6 who observe several additional intense lines. These lines are definitely due to
impurities.
The Raman active molecular vibrations of AQ (in-plane
12 ag and 11 b3g; and out-of-plane 4 bl, and 6 bSg)are
1202
The Journal of Physical Chemistry, Vol. 83, No. 9, 1979
Goodman et al.
TABLE IV: Assignment of the IR Single Crystal Spectra of 9,lO-Anthraquinone (cm-l)
AQ-h,
au
v34
obsda
calcdb
obsda
calcdb
1010
800
755
638
816
728
640
446
135
210
750
9 40
850
7 37
492
146
112
124
122
97
46
11
3080
3040
1681
1594
1455
1310
1304
1168
(1053)
40 I
236
307 6
3057
1698
1607
1460
1296
1175
1124
818
507
208
2295
2275
1676
1568
1400
1120
1021
872
(8951
39 5
222
2288
2280
1697
1579
1357
1015
1171
8 69
7 66
481
197
785
165
5
26
55
190
283
296
158
12
14
788
777
1
28
103
281
4
255
52
26
11
3075
3045
1576
1475
1330
1285
1205
1145
9 35
624
390
3074
3050
1597
1477
1392
1307
1158
1041
959
618
37 7
2295
2279
1550
1405
1310
1243
955
828
922
601
382
2286
2276
1558
1412
1339
1271
854
811
9 30
587
376
780
765
26
70
20
42
250
317
13
23
8
788
774
39
65
53
36
304
230
29
31
1
967
798
67 1
47 2
339
137
845
743
562
398
348
160
813
724
555
411
337
128
125
72
131
92
27
7
94
74
116
61
2
9
v37
'38
b1U
v39
'40
'41
'42
v43
'44
V45
'46
v47
'48
'49
b*u v 5 0
v51
'52
'53
'54
'55
'56
' 5 7
'58
'59
'6Q
b3U ' 6 1
'62
'63
'64
'65
'66
Reference 7.
,
deuteration shift
calcdb
'35
36
AQ-d,
obsda
970
815
69 3
490
37 5
167
References 12-14.
assigned in Tables I1 and 111. IR vibrations are listed in
Table IV with the Mulliken notation used throughout.
Assignments are made by comparison with AQ-d8and with
the NCA.
In the 100-500-~m-~
region, NCA predicts nine fundamentals, seven ring deformations, and two C=O modes;
nine are observed, counting the 150/156-cm-l pair as one
band. The unpolarized bands at 156 and 419 cm-l are
assigned b2 the perpendicularly polarized bands at 239
and 440 cm-T are assigned to bl,. All are in good agreement
with the calculated position and with isotope shifts. The
bands at 250 and 449 cm-l are tentatively assigned as b3g
and b2ginstead of possible factor group pairs of the 239and 440-cm-l bands, respectively, even though the isotope
shifts within the pairs are identical. The latter assignment
would leave two missing bands in this region. The 301and 364-cm-l bands are assigned ag and b3 , respectively,
since this order agrees better with NCA. $he very strong
band at 475 cm-l is assigned to ag (ull).
Five fundamentals are calculated in the 600-850-cm-l
region; seven bands are observed. The strong pair of
parallel polarized bands at 684 and 676 cm-' shift to 654
and 652 cm-l, respectively, on deuteration based upon their
intensities. The more intense 684-cm-l band is assigned
to ag (vl0) and the less intense 676-cm-' band to b3g(ual).
The band at 770 cm-l is perpendicularly polarized and
assigned to uI4 (big). The band at 795 cm-l is assigned to
an impurity since Singh and Singh observed a relatively
strong signal at this frequency.
The room temperature band at 819 cm-l is unpolarized
and splits into two bands at 817 and 820 cm-I at 5 K. This
band is assigned as a b2gfundamental. It is identified with
one or both of the 592/599-cm-l pair in AQ-d8 giving an
isotope shift in agreement with NCA calculation.
In the 900-1130-~m-~
region five bands are predicted.
The very intense band at 1030 cm-l is the % (u8) mode and
is assigned to 814 cm-l in AQ-d8. The strong parallel
polarized band at 924 cm-l is assigned to bSg ( u ~ and
~)
identified with the 901-cm-' band in AQ-d8, in close
agreement with NCA. The b3g( ~ 2 9 )mode is assigned to
the slightly parallel polarized 1082-cm-' band in AQ and
the weak 830-cm-' band in AQ-$. The bands at 978 and
990 cm-l are tentatively assigned to blg and bZgvibrations,
respectively.
In the 1140-1350-cm-' region, six fundamental vibrations
are predicted. Twelve bands are actually observed, but
four are marginally detectable (Table V). Ignoring these
and obvious combinations the 1144-cm-' band in AQ and
the 854-cm-l band in AQ-d8 are assigned to age(ug) in close
agreement with NCA. The 1173/1178-~m-~
p a r is assigned
to a factor split ag (u7) fundamental, identified with the
1087/1095-~m-~
pair in AQ-d8. The bands at 1212 and 1317
cm-' in AQ are assigned to ap. The bands at 1308 and 1326
cm-' are both tentatively assigned to bSg.
Four fundamentals are predicted in the 1400-1860-~m-~
region. The very intense band at 1665 cm-l is assigned to
the ag C=O stretching mode ( u J . The ag fundamental (u4)
is assigned to the strong lines a t 1596 (AQ) and 1569 cm-'
(AQ-d8). Firm assignment of weak b, modes in this region
is difficult due to the large number of combination bands
possible in this region.
Complete analysis of the Raman spectra of AQ a t 5 K
is given in Table V where all combinations are listed. The
very weak bands observed by Ranasen and Stenman at
211, 226, 258, 575, 917, 1243, 1440, and 1480 cm-' are
absent at 5 K but appear close to twice the noise level a t
The Journal of Physical Chemistry, Vol. 83, No. 9, 1979
Vibrational Spectra of Anthraquinone
500
30 0
400
1203
DO cm-’
200
Flgure 2. Raman spectra of AQ-hs in the 100-500-cm-’ region: (A) 5 K, (B) 100 K, (C) room temperature.
Figure 3. AQ-h, phosphorescence spectra: slowly cooled,
M in n-hexane at 4.2 K.
I
,
s
I
m
w
4800
4750
Figure 4. AQ-h8 phosphorescence spectra: fast cooled,
4700
4650
4600
M in n-hexane at 4.2 K.
room temperature. We conclude that these lines are not
intrinsic to AQ and discard any assignments based on
them. A portion of the Raman spectra of AQ (100-500
cm-’) a t -300, -100, and -5 K is shown in Figure 2.
The increased splitting of the 150-cm-l line upon decrease
in temperature is shown.
B. Phosphorescence Spectra. The lowest electronic
state of AQ has been assigned as a 3B1,435which gains
intensity through vibronic coupling with an upper state
via blu, bZu,and bSuvibrations. Analysis of the spectra was
based on the IR ground state vibrational frequencies by
Pecile and Lune113 and new Raman data. The IR spectra
have since been reassigned by Gazis, Heim, Meister, and
Dorr7 (reproduced for convenience in Table IV). The
1204
Goodman et al.
The Journal of Physical Chemistry, Vol. 83, No. 9, 1979
TABLE V: Vibrational Analysis of the Raman Spectra
of 9,lO-Anthraquinone Powder a t 5 K
v , cmre1 int
assignment
38
63
65
74
92
150
156
239
250
302
364
418
421
440
449
475
654
67 6
684
770
793
795
817
15
29
26.7
17
3.5
1.7
4.1
4.1
4.7
1.5
2.1
0.23
0.17
0.87
0.92
12.2
0.4
2.0
7.0
1.85
sh
0.06
0.4
820
900
924
978
0.6
0.2
1.2
0.5
992
1006
1014
1023
1030
1082
1100
0.52
0.23
0.7
sh
21.0
0.6
0.2
1144
1164
1173
1178
1206
19.0
0.2
8.7
31.4
sh
v,(1
cm-I
u14;
t u s , = 791; b,,
u d 0 t u 4 , = 797;b3,
u~~ t v , =~ 813; b,, or
2 x u,, = 814
V I , ; bz,
u , , t u6,= 897
b3g
'30;
2x
u6, =
1.2
0.6
1243
1308
1310
0.2
0.7
sh
1318
1326
1400
1429
1450
1460
1479
1560
2.3
0.35
0.2
1570
1580
1584
1596
1631
1634
1640
1650
1665
1702
1738
980 or
u I o t u I z = 985; A,
u,, t v s 9 = 996; b,,
u , , t u l , = 1004; a,
u j 9 t u~~ = 1014; a,
ag
u , t~ u 6 2 = 1083; b,,
u,, + u s 8 = 1102; b,, or
v 4 , + u , , = 1100; b,,
v , ; a,
u,;
u,;
a,
u 6 , t u b U=
v6;
1205; b,, or
t u , , = 1206; b,,
u,,
1212
1217
ag
u , t
~ u4, = 1220; b2, or
u , , t u h 2 = 1220; b,,
u , t
~ u,, = 1310; b,,
u d 6 + u j 7 = 1312; b,, or
v F St u j , = 1310; b,,
u , ; a,
uq7
+
~
6
=6 1428; b2g
u , ~t u j , = 1452; b,,
0.6
0.2
0.2
sh
2.4
20.0
0.3
0.3
0.8
100.0
TABLE VI: Vibrational Analysis of the Phosphorescence
Spectrum of 9,10-Anthraquinone-h, in n-Hexane at 4.2 K
ground
state vibrnC
+ u 6 , = 1477; b,,
u , t~ u,, = 1558; b,, or
v j s t u,, = 1559;a,
u,,
u,;
a,
uj,
+ u6,=
2x
u B Z = 1630;a
u d 6 t u S 2=
1635;Pbl,
1642; b i g
v , ; a, totally symmetric C=O str
u , ~ u s , = 1705; b,,
+
0.2
availability of the new ground state vibrational data
discussed in section IIIA warrants a new vibrational
analysis of the phosphorescence spectra.
Further, in the n-hexane 4.2 K phosphorescence spectra,
21 783
21 763
21 743
21 724
21 707
21 616
21 555
21 529
21 371
21 266
21 259
21 1 8 5
21 1 6 3
21 140
21 096
21 089
21 078
21 058
20 992
20 970
20 838
20 796
20 628
20 613
20 520
20 490
20 476
20 463
20 444
20 432
20 421
20 327
20 301
20 288
20 204
20 198
20 180
20 152
20 101
Av,
cm-'
assignmentb
0
20
40
59
76
167
228
254
412
517
524
598
620
643
687
694
7 05
725
791
8 13
945
987
1155
1170
1263
1293
1307
1320
1339
1351
1362
1456
1482
1495
1576
1585
1603
1631
1683
0-0; principle site
0-lattice
0-1at ti ce
0-lattice
0-lattice
0-u,,; o p skeletal def
0 - v , , ; ip skeletal def
0 - u ,,-lattice
0-06 6 - ~I 6 ; 0-b 3U-b,g
site; 0-620 t 1 0 3
site; 0-620 t 96
O - V ~ , - U , ,O-b3g-bIu
;
O-v,,
0 - u ,,-lattice
site; 0-791 + 104
site; 0-791 t 96
v,
cnl-.___
167
236
62 6
O-'63
708
0 - u , ,-lattice
O-uSz;skeletal def
816
0-u,,-lattice
0 - u , ,skeletal
;
def
0-u3 2 - ~ 0-b 3g-b l u
0 - u s , ; CH bend
0-u,,; ring str
0-u ,
o-u,,
4
0-u,,;ring str
site; 0-1456 t 105
site; 0-1456 t 92
0-u,,;
ring str
0-u,,-lattice
0-u ,-u ,o; 0-b 3u-ag
0-u,,;
ring str
0 - u , , ; ring str
0-v,,-lattice
0-v,,-u,;
0-bju-ag
0-u,, ; assymetric
C = O str
0-u,,-lattice
935
1145
1168
1304
1310
1330
1455
1576
1594
1681
20 077 1706
19 873 1910
19 836 1947
19 818 1965
19 738 2045 O - U , , - U3 2 ; 0-b lu-b 3u
1 9 714 2069 0 - U,-v, 3 2 -lattice
19 486 2297 O-U,,-U,;O-b2,-ag
,;
19 307 2476 O - U , ~ - U0-b,,-a,
~
19 292 2491 0-u,z - ,-lattice
1 8 945 2838 0-u,,-u ,;0-b , -ag
18 922 2861 O-U,,-U,-lattice
18 836 2947 0-u,,-u ; 0-b 2 u-ag
18 644 31 39 O-U,,-U,;0-b,,-a,
18 544 32 39 site; 0-3345 t 1 0 4
18 537 3246 site; 0-3345 + 96
18 517 3266 O-U,,-U 3 ; O-blu-ag
1 8 510 377 3
18 505 3278
1 8 4 7 2 3311
18 438 3345 0-u,,-u,;
0-b,,-a,
18 414 3369 0-v,,-u,-lattice
1 8 072 3711 O - U ~ ~ - U ~ - U ~ ~
bIU
bIU
1 7 824 3959 0 - u 4 , - 2 X U ,
1 7 713 4070
bIU
17 286 4477 O - I J , ~ - V ~ - U ~
Assignments are based on
a Vacuum corrected.
Single
cround state vibrations of ref 7 and this work.
crystal IR frequencies at room temperature.
the possibility of combination bands involving three quanta
of a bl, mode at 687 cm-' was raised. This band was
The Journal of Physical Chemistry, Vol. 83, No. 9, 1979
Quenching of Benzene Fluorescence
1205
cation from this laboratory, they were assigned as 3 X u49
made possible by higher order vibronic coupling mechanisms. We conclude that although these higher order
vibronic interactions might exist, they are not manifested
in the phosphorescence spectra of AQ in n-hexane at 4.2
interpreted as evidence for nonadiabatic interactions.
Other bands at 517,524,1263,1293,1351,1362,1947,1965,
3239, and 3246 cm-' could not be interpreted.
We reexamined the phosphorescence spectra of AQ in
n-hexane at 4.2 K using different concentrations and
cooling rates. Figure 3 shows the high energy region of the
phosphorescence spectra of 1 X loT5M AQ in n-hexane
slowly cooled by hanging the sample in an inner liquid
nitrogen cooled dewar and then slowly adding liquid
helium. Figure 4 shows the phosphorescence spectra of
1X
M AQ in n-hexane. Rapid cooling was affected
by immersing the sample directly into liquid helium.
The 517,524-cm-' and 687,694-cm-l pairs are enhanced
in the concentrated, fast-cooled sample. This secures their
assignments as secondary sites. The 517-cm-l line is
separated from the strong 620-cm-l line by 103 cm-l and
the 524-cm-' band is separated from the 620-cm-l one by
96 cm-l. These spacings are preserved for the 687- and
694-cm-' mode from the strong 791-cm-l (b3J mode and
the 1351/1362-cm-l pair from the medium intense
1456-cm-l line. All. others are accounted for and the
modified vibrationd analysis of the AQ phosphorescence
in n-hexane at 4.2 K is given in Table VI.
The data presented in this section show the 687- and
694-cm-l bands as [secondary sites. In a previous publi-
K.
References and Notes
(1) Supported by National Science Foundation Grant CHE 76-23813.
(2) Taken in part from the senior thesis of K.K.L., Rutgers University,
1977. Department of Chemistry, Harvard University, Cambridge, MA.
Abbott Diagnostics, Dallas, TX 75247.
0. Khalil and L. Goodman, J. Phys. Chem., 80, 2170 (1976).
K. Drabe, H. Vesnvliet, and D. Wiersma, Chem. Phys. Lett., 35, 469
(1975).
S. N. Singh and R. S.Singh, Spectrochim. Acta, Part A , 24, 1591
(1968).
E.Gazis, P. Heim, Ch. Meister, and F. Dorr, Spectrochlm. Acta, Part
A , 26, 497 (1970).
C. Pecile and B. Lunelli, J . Chem. Phys., 46, 2109 (1967).
F. Stenman, J. Chem. Phys., 51, 3413 (1969).
Y. Miyazaki and M. Ito, Bull. Chem. SOC. Jpn., 46, 103 (1973).
J. Rasanen and F. Stenman, Phys. Fenn., 10, 183 (1975).
N. Strokach, E. Gastilovich, and D. Shigorin, Opt. Spectrosc., 30,
22 (1971).
N. Strokach, E. Gastilovich, and D. Shigorin, Opt. Spectrosc., 31,
30 (1971).
N. Strokach, E. Gastilovich, and D. Shigorin, Opt. Spectrosc., 30,
238 (1971).
G. M. Badger, J. Chem. Soc., 764 (1947).
Quenching of Benzene Fluorescence in Pulsed Proton Irradiation. Temperature
Dependencet
M. 1.. West" and J. H. Miller
Radiologicai Physics, Baftelle Pacific Northwest Laboratories, Richiand, Washington 99352 (Received November 21, 1977;
Revised Manuscript Received January 8, 1979)
Publication costs assisted by the US. Department of Energy
Dilute solutions of benzene in cyclohexane were irradiated with subnanosecond pulses of protons and changes
in the time-resolved emission are studied as a function of temperature. Measurements were also made for
ultraviolet excitation and the activation energy for quenching by solvent perturbations is compared to other
values reported in the literature. An analysis of the radioluminescencedata based on dynamic quenching of
excited states by proton induced free radicals suggests that most of the temperature dependence is from thermally
activated solvent perturbations present under both proton and ultraviolet excitation. The experimental
measurements are compared to model predictions and the temperature dependence of model parameters is
discussed.
The study of fluorescence from excited molecules
provides a useful technique for investigating the transport
and transformation of energy in condensed systems.
Pulsed radioluminescence, in particular, can be used to
probe the early physical-chemical events following deposition of ionizing radiation.
In an earlier publication,l we reported on the fluorescence decay of benzene in cyclohexane for proton and
ultraviolet excitation and found the decay for proton
excitation to be nonexponential. The decay for proton
excitation was shown to be consistent with an intratrack
quenching from radicals that were created along the individual particle tracks. In a more recent study,2 we
developed a model for this intratrack quenching which
included radical recombination as well as diffusional
'This paper is based on work performed under United States Energy
Research and Development Agency Contract EY-76-C-06-1830.
0022-3654/79/2083-1205$01
.OO/O
expansion of the track core to explain the observed decrease in quenching rate with increasing time. Fluorescence decay was studied for incident proton energies of
0.3-1.9 MeV and the energy dependence of model parameters was shown to be a consequence of the energy
dependence of the incident proton stopping power.
In this paper, we report on a further investigation of this
quenching mechanism through a study of the temperature
dependence of fluorescence decay. Fluorescence response
curves are obtained for both protons and ultraviolet excitation. Our UV measurements are compared to other
values reported in the literature. We then discuss the
temperature dependence of model parameters and make
a comparison to the experimental data.
Experimental Section
The experimental apparatus is the same as that discussed in previous publications.l>* Subnanosecond proton
0 1979 American
Chemical Society