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
Chemical OIL (COIL) Cl2+НО2
-HCl + Cl-+О2(1 ) PО2 100 Тор,
=[О2(1)]/[O2]50 %
Discharge OIL (DOIL)
О2(Х) + е О2(1 ) + е PО2 10 Тор,
20 %
O3-SF6-N2O О2(а1 )-O(1D)-I2(или CH3I)
UV photolysis Photolytic OIL (PhOIL) О3 + hv О2(1 ) + O(1D)
PО2 1 Тор,
90 %
О2
+
-О2(1 ), О
NO2 I2
Nozzle
Resonator
О2
ENERGY LEVELS OF I, O2, I2, H2O
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 23
O2(1) + I(2P3/2) O2(
3) + I(2P1/2)
O2(3) + I(2P1/2) O2(
1) + I(2P3/2)
7.8×10-11
2.6×10-11
I atoms formation 45
I2(X) + O(3P) IO+ I(2P3/2)
IO + O(3P) O2(3) + I(2P3/2)
1.4×10-10
1.5×10-10
I(2P1/2) quenching
6789
1011
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
1.1×10-13
3.8×10-11
???
К(Т)?
O3 formation121314
O2 + O2 + O(3P) O3 + O2
O(3P) + O(3P) + O2 O3 + O(3P)
O(3P) + O2 + Ar O3 + Ar
5.9×10-34 cm6/s5.9×10-34 cm6/s5.9×10-34 cm6/s
O3 removal151617
I(2P3/2) + O3 IO + O2
O2(1) + O3 O2 + O2 + O(3P)
O2(1) + O3 O2(
1) + O3
1.210-12
1.510-11
3.310-12
IO +IO reaction18
19
IO + IO O2 + 2 I(2P3/2)
IO2 + I(2P3/2)
IO + IO + M I2O2 + M
8×10-12
3.2×10-11
5.6×10-30 cm6/s
O2(a1) quenching 20 O2(
1) +O(3P) + O2 2O2 + O(3P) ?
O(3P) scavenge 21 O(3P) + NO2 O2 + NO 9.710-12
The low-pressure flow cell
apparatus with a jet-type SOG
Dependence of the I* concentration on the distance along the flow for
w=3 %, O2:N2=1:1
Quenching of O2(1) has a minimal effect
on the I2 dissociation rate
Reducing [O2(1)] by an order of magnitude caused a slight increasing of the dissociation time
0 5 10 15 20
0.0
0.5
1.0
1.5
CO2:O
2=0,92:1, P
c=2 Torr
CO2:O
2=1,4:1, P
c=2,4 Torr
CO2:O
2=1,84:1, P
c=2,8 Torr
CO2:O
2=2,3:1, P
c=3,2 Torr
CO2:O
2=2,8:1, P
c=3,7 Torr
NI*
, 1014 cm-3
L, cm
O2(1) I*
Testing role of O2(1) by addition of CO2
Role of I2(B) in the iodine dissociation
Branching fraction
8.21
dλ
dλ
I
I768
758Xb
718
480XB
Xb
XB
B=5105 s-1 , b=0.08 s-1 bb bI
I
)]([(O
(B)][I
2
B2
X
XB
387
b
cm108.3)106.1(bI
I
)]([O(B)][I 2X
XB2
I2(A, A') + O2(a) I2(1Π1u) + O2(X) I + I + O2(X), approx=100 % I2(B) + M I + I + M, < 1 %
COIL active medium luminescence spectra in the visible range recorded with a resolution of 1 nm at Pc = 2.3 Torr, I2 =0.5%, N2:O2=1:1
Estimation of excitation probabilitiesfrom Barnault et al. measurements
I*+ I2 I+I2(X,v)
v -excitation probability of v-th
vibrational level
m≤v≤n=
v250.110<v230.9 (0 for dashed curve)
Standard dissociation model with v25 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.
n
mvv
Pump-probe technique used to study OIL kinetics
Monochromator Ge
Digital Oscilloscope
Nd/YAG Pumped Dye Laser
Delay Generator
Pump
Fluorescence cell
I2+Ar
Light baffles
Quenching gas
Excimer laser
Rate of I2(A') quenching (Rq) depends on CO2 partial pressure РСО2 at PAr=50 Torr, РI2=0.013 Torr
and T=300 K
KCO2 = 8.510-13 cm3/s KAr = 2.710-14 cm3/s
KO2 = 6 10-12 cm3/s
KI2 = 4.810-11 cm3/s
N2O,NO2 or O3
Pump
193 or 248 nm
Powermeter
1268 nm filter
Ge photo-detector
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
Branching fraction for O2(1) from O(1D)+N2O & O(3P)+N2O
3O
O2N
193
248a, I
I
E
E08.3
Typical temporal profiles of the 1268 nm emission intensities for the N2O photolysis experiment (IN2O) –PN2O=207 Torr, PAr=407 Torr and for the O3 photolysis experiment (IO3)- PN2=755 Torr, PAr=1.3 Torr
#IN2O
mV
IO3 mV E193
mJ
E248
mJ
a
12345
0.150.150.140.140.11
0.350.350.330.510.33
14.415.814.21611
11.211.211.218.411.2
1.030.941.030.971.05
YieldO(1D) + N2O N2 + O2(1) 100 %
O(3P) + NO2 NO + O2(1) <10 %
Quenching I(2P1/2) by О(3Р), О3
N2O + 193 нм 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) +О(3P)I(2P1/2) + O3 products
I(2P1/2 ) I(2P3/2 )+ h (= 1315 nm)
Dashed lines are calculations at KO=1.210-11 cm3/sKO3=1.810-12 cm3/s
0.0000 0.0001
0.00
0.01
0.02
0.55
0.33
0.22
0.13
Time, sec
PO3
/Torr
=248 nm
E=22 mJ/cm2
0.067
Quenching I(2P1/2) by NO2, N2O4 & N2OCF3I + h (248 nm) CF3 + I(2P1/2) NO2=2.85x10-19 cm2
NO2 + h (248 nm) O + NO NO2=2x10-20 cm2
N2O4 + h (248 nm) NO2+ NO2 N2O4= 80NO2
O+ NO+NO2
KN2O4= (3.70.5)×10-13 cm3/sKNO2= (2.90.3)×10-15 cm3/sKN2O= (1.30.1)×10-15 cm3/s
0 20 40 60 80
0,0000
0,0005
0,0010
0,0015
t, sec
Em
isso
n in
tens
ity
at
268
nm
PAr
=92 Torr, PO2
=680 Torr
PAr
=200 Torr, PO2
=573 Torr
PAr
=305 Torr, PO2
=467 Torr
PAr
=250Torr, PO2
=521 Torr
calcul. calcul. calcul. calcul.
Temporal emission intensity of O2(1) at PO3=2.4 Torr, Ptot=773 Torr. Dashed lines are calculations at K=1.1x10-31 cm6/s.
0 20 40 60 80
0,000
0,001
t, sec
PAr
= 0 Torr, PO2
= 762 Torr
PAr
= 108 Torr, PO2
= 654Torr
PAr
= 249 Torr, PO2
= 513 Torr
calcul. calcul. calcul.
Em
issi
on in
ten
sity
at
600
nm
NO2 emission intensity near to 600 nm at PO3=2.4 Torr, PN2O=2.8 Torr, Ptot=762 Torr
Quenching of O2(a1) in the presence О2 and O(3P)
O3 +h(248 nm) O(1D) + O2(1) O(3P) + O2(X)O2(1) O2(3)+ h (1268 nm)
O(3P) + O2(1) + O2 O(3P) + 2O2
Conclusions
Standard dissociation model with v25 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.
The total excitation probabilities of I2(X,v) in
reaction I* + I2 I + I2(X,v>10) are v25 0.1
and 10<v<25 0.9
I2(B) and takes a minor part in iodine dissociation and O2(b) does not play a noticeable role in I2(B) formationI2 dissociation pathway involving O2(b) state is not major channel
Measured kinetic constants:
I2(A) + CO2 I2(X) + CO2 (8.50.9)10-13 cm3/s
I2(A) + O2 I2(X) + O2 (6.00.6)10-12 cm3/s
I2(A) + I2 I2(X) + I2 (4.80.9)10-11 cm3/s
I2(A) + Ar I2(X) + Ar (2.70.3)10-14 cm3/s
О2(b) + CO2 О2(а) + CO2 (6.10.5)10-13 cm3/s
О2(b) + O3 products (1.90.2)10-11 cm3/s
I(2P1/2) + O(3P) I + O(3P) (1.2±0.1)10-11 cm3/s
I(2P1/2) + O3 products (1.8±0.4)10-12 cm3/s
I(2P1/2) + NO2 I + NO2 (2.9±0.3)10-15 cm3/s
I(2P1/2) + N2O4 I + N2O4 (3.7±0.5)10-13 cm3/s
I(2P1/2) + N2O I + N2 O (1.3±0.1)10-15 cm3/s
O2(a1) + O(3P) + O2 O(3P) + 2O2 (1.1±0.2)10-31 cm6/s
Yield of O2(a1) in reactionsO(1D) + N2O N2 + O2(
3) or O2(1) - 1±0.12
O(3P or 1D) + NO2 NО + O2(3) or O2(1) - < 0.1
Conclusions
O2(a,v=3)+I2(X)O2(X)+2I (97)O2(a,v=1)+I2(X,v15)O2(X)+2I (102)O2(a,v=2)+I2(X,v8) O2(X)+2I (103)O2(b) + I2(X) O2(X) + 2I (21)
Developed I2 dissociation model
I* + I2 I + I2(10<v<25) (33)I2(10<v<25)+O2(a)O2(X)+I2(A’,A)
(101)
O2(a,v=1)+I2(X)O2(X)+I2(A’) (95)O2(a,v=2)+I2(X)O2(X)+I2(A) (96)O2(a)+I2(A’,A) O2(X)+2I (25)
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
Heidner et al. modelO2(a)+I2(X)O2(X)+ I2(20<v<45) (32)I2(20<v<45)+O2(a)O2(X)+2I (34) I* + I2 I + I2(25<v<45) (33)
Conclusions
A model that involves excitation of I2(A’,A) byreactionsO2(a,v=1)+I2(X)O2(X)+I2(A’) (95)O2(a,v=2)+I2(X)O2(X)+I2(A) (96)O2(a)+I2(A’,A) O2(X)+2I (25)I* + I2 I + I2(10<v<25) (33)I2(10<v<25)+O2(a)O2(X)+I2(A’,A) (101)yields results that are in reasonableagreement with the flow tube experiments.