Paul Beaud, Peter P. Radi, Dieter Franzke, Hans-Martin Frey, Bernhard Mischler, Alexios-Paul Tzannis, and Thomas Gerber, "Picosecond investigation of the collisional deactivation of OH A2Σ+(v′ = 1, N′ = 4, 12) in an atmospheric-pressure flame," Appl. Opt. 37, 3354-3367 (1998)
The collisional deactivation of the laser excited states A2Σ+(v′ = 1, N′ = 4, 12) of OH in a
flame is studied by measurement of spectrally resolved fluorescence
decays in the picosecond time domain. Quenching and depolarization
rates, as well as vibrational energy-transfer (VET) and rotational
energy-transfer (RET) rates are determined. An empirical model
describes the temporal evolution of the quenching and VET rates that
emerge from the rotational-state relaxation. Fitting this model to
the measured 1–0 and 0–0 fluorescence decays yields the quenching and
VET rates of the initially excited rotational state along with those
that correspond to a rotationally equilibrated vibronic-state
population. VET from the higher rotational state (N′ =
12) shows a tendency for resonant transitions to energetic
close-lying levels. RET is investigated by analysis of the temporal
evolution of the 1–1 emission band. The observed RET is well
described by the energy-corrected sudden-approximation theory in
conjunction with a power-gap law.
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Transitions Overlapping the Bandwidth of the Laser Pulse,
the Corresponding Excited States, and Their Contributions p
to the Overall Vibronic Excitation for Q14 and
Q112 Excitation
Ref. 17.
See text.
Ref. 28.
Estimates from Ref. 17.
Table 5
ECS Parameters γ, lc, and
k0 Depending on the
Modela
RET Model
Fitted Data
γ
lc (Å)
k
0
(×108 s-1)
χ2
N′ = 4
N′ = 12
ECS
N′ = 4, 12
1.26 ± 0.04
1.1 ± 0.1
31 ± 4
1.0
1.0
N′ = 4
1.27 ± 0.07
1.4 ± 0.5
33 ± 8
0.99
1.4
N′ = 12
1.33 ± 0.12
1.3 ± 0.3
45 ± 29
1.9
0.99
Sudden
N′ = 4, 12
1.15 ± 0.05
–
15 ± 1
3.8
3.3
N′ = 4
1.26 ± 0.08
–
27 ± 5
1.15
11.6
N′ = 12
1.01 ± 0.06
–
8 ± 2
9.6
1.4
The first row shows the result obtained
when the ECS model was fitted to both data sets (N′ = 4
and N′ = 12) simultaneously. For comparison, the
result obtained by fitting each data set individually or by use of the
sudden approximation are also shown. The sums of least-squares
errors χ2 are normalized and calculated separately for
each data set (see text).
Table 6
Total RET Rates kL and Relative
State Relaxation Rates kR (in units of
108 s-1)a
Rotational State
Detected Transition
kR
kL
Rate Model
ECS Model
N′ = 4
Q14
26.5 ± 2.0
57 ± 4
59.6
P15
36.5 ± 2.4
58 ± 5
–
N′ = 12
Q112
12.6 ± 1.5
30 ± 2
28.3
P113
11.8 ± 1.5
32 ± 2
–
Columns 3 and 4 obtained by fitting the
time-dependent rate model [Eqs. (11) and (12)] to the lines
emitted by the laser-excited rotational state; column 5, the
corresponding total RET rates calculated with the ECS result.
Tables (6)
Table 1
Transitions Overlapping the Bandwidth of the Laser Pulse,
the Corresponding Excited States, and Their Contributions p
to the Overall Vibronic Excitation for Q14 and
Q112 Excitation
Ref. 17.
See text.
Ref. 28.
Estimates from Ref. 17.
Table 5
ECS Parameters γ, lc, and
k0 Depending on the
Modela
RET Model
Fitted Data
γ
lc (Å)
k
0
(×108 s-1)
χ2
N′ = 4
N′ = 12
ECS
N′ = 4, 12
1.26 ± 0.04
1.1 ± 0.1
31 ± 4
1.0
1.0
N′ = 4
1.27 ± 0.07
1.4 ± 0.5
33 ± 8
0.99
1.4
N′ = 12
1.33 ± 0.12
1.3 ± 0.3
45 ± 29
1.9
0.99
Sudden
N′ = 4, 12
1.15 ± 0.05
–
15 ± 1
3.8
3.3
N′ = 4
1.26 ± 0.08
–
27 ± 5
1.15
11.6
N′ = 12
1.01 ± 0.06
–
8 ± 2
9.6
1.4
The first row shows the result obtained
when the ECS model was fitted to both data sets (N′ = 4
and N′ = 12) simultaneously. For comparison, the
result obtained by fitting each data set individually or by use of the
sudden approximation are also shown. The sums of least-squares
errors χ2 are normalized and calculated separately for
each data set (see text).
Table 6
Total RET Rates kL and Relative
State Relaxation Rates kR (in units of
108 s-1)a
Rotational State
Detected Transition
kR
kL
Rate Model
ECS Model
N′ = 4
Q14
26.5 ± 2.0
57 ± 4
59.6
P15
36.5 ± 2.4
58 ± 5
–
N′ = 12
Q112
12.6 ± 1.5
30 ± 2
28.3
P113
11.8 ± 1.5
32 ± 2
–
Columns 3 and 4 obtained by fitting the
time-dependent rate model [Eqs. (11) and (12)] to the lines
emitted by the laser-excited rotational state; column 5, the
corresponding total RET rates calculated with the ECS result.
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