RECENT STUDIES OF OXYGEN-IODINE LASER KINETICS

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RECENT STUDIES OF OXYGEN-IODINE LASER
KINETICS
Azyazov V.N. and Pichugin S.Yu. P.N. Lebedev
Physical Institute,Samara Branch, Russia
Heaven M.C. Emory University, Atlanta, USA
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Chemical OIL (COIL) Cl2??2-?HCl Cl-?2(1? )
P?2? 100 ???, ???2(1?)/O2?50
Nozzle

Discharge OIL (DOIL) ?2(?) ? ? ?2(1? ) ?
P?2? 10 ???, ?? ? 20
?2
?2
?2(1? ), ?
-
Resonator
NO2 I2
UV photolysis
Photolytic OIL (PhOIL) ?3 hv ? ?2(1? ) O(1D)
P?2? 1 ???, ?? ? 90
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ENERGY LEVELS OF I, O2, I2, H2O
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List of reactions that of importance in the DOIL
and PhOIL
Process Rate constant, cm3 s-1
O2(1?) formation 1 O2(3?) e ? O2(1?) e
EE energy exchange 2 3 O2(1?) I(2P3/2) ? O2(3?) I(2P1/2) O2(3?) I(2P1/2) ? O2(1?) I(2P3/2) 7.810-11 2.610-11
I atoms formation 4 5 I2(X) O(3P) ? IO I(2P3/2) IO O(3P) ? O2(3?) I(2P3/2) 1.410-10 1.510-10
I(2P1/2) quenching 6 7 8 9 10 11 I(2P1/2) O2(1?) ? I(2P3/2) O2(1?) I(2P1/2) I2(X) ? I(2P3/2) I2(X) I(2P1/2) O(3P) ? I(2P3/2) O(3P) I(2P1/2) O3 ? products I(2P1/2) NO2, N2O4 ? I(2P3/2) NO2, N2O4 I(2P1/2) N2O ? I(2P3/2) N2O 1.110-13 3.810-11 ? ? ? ?(?)?
O3 formation 12 13 14 O2 O2 O(3P) ? O3 O2 O(3P) O(3P) O2 ? O3 O(3P) O(3P) O2 Ar ? O3 Ar 5.910-34 cm6/s 5.910-34 cm6/s 5.910-34 cm6/s
O3 removal 15 16 17 I(2P3/2) O3 ? IO O2 O2(1?) O3 ? O2 O2 O(3P) O2(1?) O3 ? O2(1?) O3 1.2?10-12 1.5?10-11 3.3?10-12
IO IO reaction 18 19 IO IO ? O2 2 I(2P3/2) ? IO2 I(2P3/2) IO IO M ? I2O2 M 810-12 3.210-11 5.610-30 cm6/s
O2(a1?) quenching 20 O2(1?) O(3P) O2 ? 2O2 O(3P) ?
O(3P) scavenge 21 O(3P) NO2 ? O2 NO 9.7?10-12
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The low-pressure flow cell apparatus with a
jet-type SOG
Dependence of the I concentration on the
distance along the flow for ?w3 , O2N211
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Quenching of O2(1?) has a minimal effecton the
I2 dissociation rate
Testing role of O2(1?) by addition of CO2

• Reducing O2(1?) by an order of magnitude
  caused a slight increasing of the dissociation
  time

O2(1?)
I
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Role of I2(B) in the iodine dissociation
COIL active medium luminescence spectra in the
visible range recorded with a resolution of 1 nm
at Pc 2.3 Torr, ?I2 0.5, N2O211
GB5?105 s-1 , Gb0.08 s-1

• Branching fraction

I2(A, A') O2(a) ? I2(1?1u) O2(X) ? I I
O2(X), approx100 ? I2(B) M ?
I I M, lt 1
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Estimation of excitation probabilitiesfrom
Barnault et al. measurements
I I2? II2(X,v) ?v -excitation probability of
v-th vibrational level ?mvn ?v?250.1
?10ltv?230.9 (0 for dashed curve)
Standard dissociation model with ?v?25 0.1 can
not provide observed dissociation rates in COIL
medium. About 20 molecules of O2(a) consumed to
dissociate one I2 molecule if standard model is
predominant dissociation pathway.
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Pump-probe technique used to study OIL kinetics
Nd/YAG Pumped Dye Laser

Quenching gas
I2Ar
Delay Generator
Monochromator
Digital Oscilloscope
Ge
Pump
Fluorescence cell
Excimer laser
Light baffles
Rate of I2(A') quenching (Rq) depends on
CO2 partial pressure ???2 at PAr50 Torr,
?I20.013 Torr and T300 K KCO2 8.5?10-13
cm3/s KAr 2.7?10-14 cm3/s KO2 6 ?10-12
cm3/s KI2 4.8?10-11 cm3/s
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Branching fraction for O2(1?) from O(1D)N2O
O(3P)N2O
O2(1?) formation N2O 193 nm ? O(1D) N2 O(1D)
N2O ? N2 O2(1?) ? O(3P) NO2 ? NO O2(1?)
? O3 248 nm ? O(1D) O2(1?) O2(1?) ?
O2(3?)1268 nm
IN2O mV IO3 mV ?E193 mJ ?E248 mJ hD,a
1 2 3 4 5 0.15 0.15 0.14 0.14 0.11 0.35 0.35 0.33 0.51 0.33 14.4 15.8 14.2 16 11 11.2 11.2 11.2 18.4 11.2 1.03 0.94 1.03 0.97 1.05
Yield O(1D) N2O ? N2 O2(1?)
100 O(3P) NO2 ? NO O2(1?) lt10
Typical temporal profiles of the 1268 nm emission
intensities for the N2O photolysis experiment
(IN2O) PN2O207 Torr, PAr407 Torr and for the
O3 photolysis experiment (IO3)- PN2755 Torr,
PAr1.3 Torr
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Quenching I(2P1/2) by ?(3?), ?3

• N2O 193 ?? ? N2 O(1D)
• O(1D) N2O ? N2 O2(1?)
• ? NO NO
• O3 248 nm ? O(1D) O2(1?)
• O(1D) CO2(N2) ? O(3P) CO2(N2)
• I2(X) O(3P) ? IO I(2P3/2)
• IO O(3P) ? O2(3?) I(2P3/2)
• I(2P3/2) O2(1?) ? I(2P1/2) O2(3?)
• I(2P1/2) O(3P) ? I(2P3/2) ?(3P)
• I(2P1/2) O3 ? products

I(2P1/2 ) ? I(2P3/2 ) h? (? 1315 nm) Dashed
lines are calculations at KO1.2?10-11
cm3/s KO31.8?10-12 cm3/s
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Quenching I(2P1/2) by NO2, N2O4 N2OCF3I
h? (248 nm) ? CF3 I(2P1/2) sNO22.85x10-19 cm2
NO2 h? (248 nm) ? O NO sNO22x10-20
cm2 N2O4 h? (248 nm) ? NO2 NO2 sN2O4
80sNO2 ? O NONO2
KN2O4 (3.7?0.5)10-13 cm3/s KNO2
(2.9?0.3)10-15 cm3/s KN2O (1.3?0.1)10-15
cm3/s
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Quenching of O2(a1?) in the presence ?2 and
O(3P)
O(3P) O2(1?) O2 ? O(3P) 2O2
O3 h?(248 nm) ? O(1D) O2(1?)
? O(3P) O2(X) O2(1?) ? O2(3?) h?
(1268 nm)

• Temporal emission intensity of O2(1?) at PO32.4
  Torr, Ptot773 Torr. Dashed lines are
  calculations at K1.1x10-31 cm6/s.

NO2 emission intensity near to 600 nm at PO32.4
Torr, PN2O2.8 Torr, Ptot762 Torr
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Conclusions
The total excitation probabilities of I2(X,v) in
reaction I I2 ? I I2(X,vgt10) are ?v?25 ? 0.1
and ?10ltvlt25 ? 0.9
Standard dissociation model with ?v?25 ?0.1 can
not provide observed dissociation rates in COIL
medium. About 20 molecules of O2(a) consumed to
dissociate one I2 molecule if standard model is
predominant dissociation pathway.
I2(B) and takes a minor part in iodine
dissociation and O2(b) does not play a noticeable
role in I2(B) formation
I2 dissociation pathway involving O2(b) state is
not major channel
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Conclusions

• Measured kinetic constants
• I2(A?) CO2? I2(X) CO2 (8.5?0.9)?10-13
  cm3/s
• I2(A?) O2? I2(X) O2 (6.0?0.6)?10-12 cm3/s
• I2(A?) I2? I2(X) I2 (4.8?0.9)?10-11 cm3/s
• I2(A?) Ar? I2(X) Ar (2.7?0.3)?10-14 cm3/s
• ?2(b) CO2? ?2(?) CO2 (6.1?0.5)?10-13 cm3/s
• ?2(b) O3? products (1.9?0.2)?10-11 cm3/s
• I(2P1/2) O(3P) ? I O(3P) (1.20.1)?10-11
  cm3/s
• I(2P1/2) O3 ? products (1.80.4)?10-12
  cm3/s
• I(2P1/2) NO2 ? I NO2 (2.90.3)?10-15
  cm3/s
• I(2P1/2) N2O4 ? I N2O4 (3.70.5)?10-13
  cm3/s
• I(2P1/2) N2O ? I N2 O (1.30.1)?10-15
  cm3/s
• O2(a1?) O(3P) O2 ? O(3P) 2O2
  (1.10.2)?10-31 cm6/s
• Yield of O2(a1?) in reactions
• O(1D) N2O ? N2 O2(3?) or O2(1?)
  - 10.12
• O(3P or 1D) NO2? N? O2(3?) or O2(1?) -
  lt 0.1

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Developed I2 dissociation model
O2(a,v1)I2(X)?O2(X)I2(A) (95) O2(a,v2)I2(X
)?O2(X)I2(A) (96) O2(a)I2(A,A) ? O2(X)2I
(25)
I I2 ? I I2(10ltvlt25)
(33) I2(10ltvlt25)O2(a)?O2(X)I2(A,A) (101)
O2(a,v3)I2(X)?O2(X)2I
(97) O2(a,v1)I2(X,v?15)?O2(X)2I
(102) O2(a,v2)I2(X,v?8) ?O2(X)2I (103) O2(b)
I2(X) ? O2(X) 2I (21)
Heidner et al. model O2(a)I2(X)?O2(X)
I2(20ltvlt45) (32) I2(20ltvlt45)O2(a)?O2(X)2I
(34) I I2 ? I I2(25ltvlt45) (33)
Potential energy curves of I2. The red and blue
arrows show the excitation pathways of energy
states lying bellow and above the I2 dissociation
limit, respectively. The inscriptions above
arrows denote the reaction producing excitation
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Conclusions
A model that involves excitation of I2(A,A)
by reactions O2(a,v1)I2(X)?O2(X)I2(A)
(95) O2(a,v2)I2(X)?O2(X)I2(A)
(96) O2(a)I2(A,A) ? O2(X)2I (25) I
I2 ? I I2(10ltvlt25)
(33) I2(10ltvlt25)O2(a)?O2(X)I2(A,A)
(101) yields results that are in
reasonable agreement with the flow tube
experiments.