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Lifetimes of Liquid benzene, toluene, and mesitylene excited by a pulsed-electron beam
CHEMICAL
Volume 4. number 4
LIFETIMES
OF
LIQUID
EXCITED
BENZENE,
BY
0. E. WAGNERtt
PHYSICS
LETTERS
1
TOLUENE,
AND
A PULSED-ELECTRON
November 1969
MESITYLENE
BEAM-t
, L. G. CHRISTOPHOROU and J. G. CARTER
Health Physics Division. Oak Ridge Xational Labmatory, Oak Ridge, Tennessee 37830, USA
Received
The Lifetimes of liquid benzene, equal to 30.3, 41.2, and 44.2 nsec.
We have
whereby
described
recently [l]
a pulsed-electron
siource
toluene. nnd mesitvlene
a method is used
to
measure the lifetime of emitting excited species
formed in organic liquids under electron impact,
We have used this apparatus and kept the intensity of the electron beam low so thay the emission is composed of a monomer (IM;
-
(%vf* 1 -
1+l
MI + kuE) component.
1969
at 25% are.
benzene,
beam
respectively. greater than or
toluene,
intensities.
and mesityiene
Various
samples
at 25OC at low and deoxygen-
atiou pracedureg have been tried
-d the results are summarized in table 1. They clearly show that oxygen content and sample purity are criti-
cal factors in lifetime measurements. The results summarized in table 1 also show that other previously published data on the lifetimes
lM1 + hvM) and an excimer IM
8 September
This has
been checked by recording the emission spectra under identical conditions as for the lifetime measurements. An increase ir, the beam intensity caused a change in the emission spectrum as reported earlier [I]. For a high intensity continuous (not pulsed) beam, emission from radiation products has been pronounced; one particular emission could be ascribed to biphenyl. In this note we report lifetimes for liquid
of
or-
ganic molecules in the liquid state or in solution may be lower than their true values. Similar conclusions have been reached by Greenleaf et al. [27, who obtained under pulsed ultraviolet excitation for the toluene 1~; - lM$ system a lifetime of 39.2 nsec at 20°C. Our present measurements show that the common lifetime of the 1M; - 1Mi system for liquid benzene, toluene, and mesitylene is. respectively, greater than or equal to 30.3, 41.2. and 44.2 nsec. REFERENCES
f Research
sponsored by the U.S. Atomic Energy
Commission under contract with Union Carbide Corporation. tt U. S. Atomic Enera Commission Postdoctoral FeIlow_
224
111L. G. Christophorou,
M-E. Bf. Abu-Zeid
Carter, J.Chem. Phys. 89 (1968) 3775.
and J. G.
121J. RGreenleaf, h1.D. Lumb and J. B. Birks, Phys. B (Pcoc. Phys.Soc.) 1 (1968) 1157.
J.
Volume 4, number 4
CHEMlCAL PHYSICS LETTERS
1 November 1969
Table 1 Lifetimes of liquid benzene, toluene. and mesitylene excited by x pulsed-electron beam
Table 1 (continued)
Benzene (99.99%) Method of deoxygenation
T
Mesitylene (nsec)
11.6; 12.1 12.5: 10.9; 13.6
12.1
A(13
15.6: 16.3
15.9
A(30)
22.4
22.4
A (60)
24.8; 25.9 26.5; 27.1; 28.9 24.9
26.3
A (0) 3)
B (3) C)
22.9; 23.4
23.1
B (5)
25.5
25.5
c (30) a)
31.8; 30.7
31.2
C (45)
31: 30.2; 29.3; 30.2 28.8; 29.0;
30.2
c(60)
28.9;
Method of deoxygenation
7 W
(nsec)
cw9
31.8
31.8
C(125)
29.6
29.8
C(125)
29.6 29.9
29.6 29.9 av = 30.3
Toluene Sample no. 1 (99.99%) A(0) a)
8.3; 8.8:
CW)
37.8: 42.7 43.1
9.8
?b) (nsec)
Sample no. 1 @9.9tQ A (0) a)
10.8; 10.0; 11.4
10.7
A(15) A(45)
17.3; 22.8
20.1
36.5
36.5
A (60)
42.5
42.5
APO)
44.1; 41.5 44.5; 46.5
44.2
Sample no. 2 @9.8%) ~(90) a)
30.3
30.3
Sample no. 3
29.5
31-i
(nsTec)
C(30) 3
36.5
C (so)
36.8
n) Bubbling tl~~?e b)
Arithmetic
(in
minutes)
36.6 ___
mean.
c) Ntimber of cycles. A) Nitrogen gas bubbling through the liquid in a nitrogen atmosphere. B) Freeze-pump-thaw technique. C) High-purity helium gas passed through z porous filter into the liquid under study and lhe helium flow arranged such that only small-size bubbles are formed. The liquid was contained in a vacuum-tight box under nitrogen atmosphere.
8.9
41.2
Sample no. 2 (99.99%) C (60) “)
35.4
ccJ0)
36.5; 37.1
36.3
Sample no. 3 (99.7%)
c (0) a)
8.8; 9.8
cm
25.7
28.7
C(30)
28.2
28.3
WO) C(120)
28.4; 29.2
28.5
28.3; 29.9
29.1
9.3
av = 25.7
225
Volume 4. number 4
LIFETIMES
OF
LIQUID
EXCITED
BENZENE,
BY
0. E. WAGNERtt
PHYSICS
LETTERS
1
TOLUENE,
AND
A PULSED-ELECTRON
November 1969
MESITYLENE
BEAM-t
, L. G. CHRISTOPHOROU and J. G. CARTER
Health Physics Division. Oak Ridge Xational Labmatory, Oak Ridge, Tennessee 37830, USA
Received
The Lifetimes of liquid benzene, equal to 30.3, 41.2, and 44.2 nsec.
We have
whereby
described
recently [l]
a pulsed-electron
siource
toluene. nnd mesitvlene
a method is used
to
measure the lifetime of emitting excited species
formed in organic liquids under electron impact,
We have used this apparatus and kept the intensity of the electron beam low so thay the emission is composed of a monomer (IM;
-
(%vf* 1 -
1+l
MI + kuE) component.
1969
at 25% are.
benzene,
beam
respectively. greater than or
toluene,
intensities.
and mesityiene
Various
samples
at 25OC at low and deoxygen-
atiou pracedureg have been tried
-d the results are summarized in table 1. They clearly show that oxygen content and sample purity are criti-
cal factors in lifetime measurements. The results summarized in table 1 also show that other previously published data on the lifetimes
lM1 + hvM) and an excimer IM
8 September
This has
been checked by recording the emission spectra under identical conditions as for the lifetime measurements. An increase ir, the beam intensity caused a change in the emission spectrum as reported earlier [I]. For a high intensity continuous (not pulsed) beam, emission from radiation products has been pronounced; one particular emission could be ascribed to biphenyl. In this note we report lifetimes for liquid
of
or-
ganic molecules in the liquid state or in solution may be lower than their true values. Similar conclusions have been reached by Greenleaf et al. [27, who obtained under pulsed ultraviolet excitation for the toluene 1~; - lM$ system a lifetime of 39.2 nsec at 20°C. Our present measurements show that the common lifetime of the 1M; - 1Mi system for liquid benzene, toluene, and mesitylene is. respectively, greater than or equal to 30.3, 41.2. and 44.2 nsec. REFERENCES
f Research
sponsored by the U.S. Atomic Energy
Commission under contract with Union Carbide Corporation. tt U. S. Atomic Enera Commission Postdoctoral FeIlow_
224
111L. G. Christophorou,
M-E. Bf. Abu-Zeid
Carter, J.Chem. Phys. 89 (1968) 3775.
and J. G.
121J. RGreenleaf, h1.D. Lumb and J. B. Birks, Phys. B (Pcoc. Phys.Soc.) 1 (1968) 1157.
J.
Volume 4, number 4
CHEMlCAL PHYSICS LETTERS
1 November 1969
Table 1 Lifetimes of liquid benzene, toluene. and mesitylene excited by x pulsed-electron beam
Table 1 (continued)
Benzene (99.99%) Method of deoxygenation
T
Mesitylene (nsec)
11.6; 12.1 12.5: 10.9; 13.6
12.1
A(13
15.6: 16.3
15.9
A(30)
22.4
22.4
A (60)
24.8; 25.9 26.5; 27.1; 28.9 24.9
26.3
A (0) 3)
B (3) C)
22.9; 23.4
23.1
B (5)
25.5
25.5
c (30) a)
31.8; 30.7
31.2
C (45)
31: 30.2; 29.3; 30.2 28.8; 29.0;
30.2
c(60)
28.9;
Method of deoxygenation
7 W
(nsec)
cw9
31.8
31.8
C(125)
29.6
29.8
C(125)
29.6 29.9
29.6 29.9 av = 30.3
Toluene Sample no. 1 (99.99%) A(0) a)
8.3; 8.8:
CW)
37.8: 42.7 43.1
9.8
?b) (nsec)
Sample no. 1 @9.9tQ A (0) a)
10.8; 10.0; 11.4
10.7
A(15) A(45)
17.3; 22.8
20.1
36.5
36.5
A (60)
42.5
42.5
APO)
44.1; 41.5 44.5; 46.5
44.2
Sample no. 2 @9.8%) ~(90) a)
30.3
30.3
Sample no. 3
29.5
31-i
(nsTec)
C(30) 3
36.5
C (so)
36.8
n) Bubbling tl~~?e b)
Arithmetic
(in
minutes)
36.6 ___
mean.
c) Ntimber of cycles. A) Nitrogen gas bubbling through the liquid in a nitrogen atmosphere. B) Freeze-pump-thaw technique. C) High-purity helium gas passed through z porous filter into the liquid under study and lhe helium flow arranged such that only small-size bubbles are formed. The liquid was contained in a vacuum-tight box under nitrogen atmosphere.
8.9
41.2
Sample no. 2 (99.99%) C (60) “)
35.4
ccJ0)
36.5; 37.1
36.3
Sample no. 3 (99.7%)
c (0) a)
8.8; 9.8
cm
25.7
28.7
C(30)
28.2
28.3
WO) C(120)
28.4; 29.2
28.5
28.3; 29.9
29.1
9.3
av = 25.7
225