1. IR Spectra of CH2OO at resolution 0
IR Spectra of CH2OO at resolution 0.25 cm-1: Assignments of ν5 and 2ν9 Bands and Overlapped Bands of ICH2OO
Yu-Hsuan Huang,1 Li-Wei Chen,1 and Yuan-Pern Lee1, 2
1 Department of Applied Chemistry, National Chiao Tung University, Taiwan
2 Institute of Atomic and Molecular Sciences, Academia Sinica, Taiwan
70th International Symposium on Molecular Spectroscopy

2. Simplest Criegee intermediate:
Importance of CH2OO
Criegee mechanism
important for the removal of unsaturated hydrocarbons and for the production of OH in the atmosphere
R. Criegee, Rec. Chem. Prog. 18, 111 (1957) +
(primary ozonide) +
stabilization
Isomerization and decomposition
Decomposition of CH2OO
HCOOH, OH, CH3, CO, CO2, etc
(Criegee intermediate)
dioxirane
methylenebisoxy
(kcal/ mol-1)
Simplest Criegee intermediate:
CH2OO
Li et al., J. Phys. Chem. Lett. 5, 13 (2014)

3. Experimental observation of CH2OO
CH2I + O2 → ICH2OO*→ CH2OO + I
Photoionization mass spectrometry
Su et al., Science 340, 174 (2013)
IR spectrum of CH2OO at R = 1 cm-1 ν8 ν6 ν4 ν3 ν5
Rotationally resolved spectrum of CH2OO:
definitive assignments of each band
rotational constants of vib. excited states
Taatjes et al., J. Am. Chem. Soc. 130, (2008)
Welz et al., Science 335, 204 (2012)

4. Experimental setup

5. Absorption spectrum at 0.25 cm-1 resolution
CH2I2/N2/O2 nm, Pt = 94 torr
1 cm-1 ν6 μs ν4 ν8 ν3 ν5
average 13 spectra
0.25 cm-1
0-25 μs
Su et al., Science 340, 174 (2013)

6. Spectral analysis: near prolate approximationb c
𝜅= 2 𝐵 −A−C A−C =−0.95 for CH2OO
κ = -1 prolate
κ = +1 oblate Cs
𝐹 𝜐,𝐽,𝐾 = 𝜈 𝜐 + (𝐴 𝜐 − 𝐵 𝜐 ) 𝐾 2 + 𝐵 𝜐 𝐽 𝐽+1
𝑩 𝝊 = ( 𝑩 𝝊 + 𝑪 𝝊 ) 𝟐
Parallel transitions
a-type
𝜈 𝐽, 𝐾 = 𝜈 0 + Δ𝐴−Δ 𝐵 𝐾 2 +∆ 𝐵 𝐽 𝐽+1
𝜈 𝐽, 𝐾 = 𝜈 0 + Δ𝐴−Δ 𝐵 𝐾 2 +(∆ 𝐵 𝐽+2 𝐵 ′ ) 𝐽+1
ΔJ = 0, Q branch
ΔJ = 1, R branch
ΔJ = -1, P branch
𝜈 𝐽, 𝐾 = 𝜈 0 + Δ𝐴−Δ 𝐵 𝐾 2 +[∆ 𝐵 𝐽−( 𝐵 ′ + 𝐵 ")]𝐽
Δ𝐴= 𝐴 ′ −𝐴“, Δ 𝐵 = 𝐵 ′ − 𝐵 “
b-type & c-type
Perpendicular transitions
𝜈 𝐽, 𝐾 = 𝜈 0 + 𝐴 ′ − 𝐵 ′ + Δ𝐴−Δ 𝐵 𝐾 2 ±2 𝐴 ′ − 𝐵 ′ 𝐾"
Q branch
A”, B”, and C” from MW
A’/A”, B’/B”, and C’/C” from calculation
Nakagima and Endo, J. Chem. Phys. 139, (2013)
VCI-5 and B3LYP/aug-cc-pVTZ
J. Chem. Phys. 142, (2015)

7. ν8 mode of CH2OO c-type → Perpendicular band of prolate QQ
CH2 wagging (ν8)
c-type
ν8 mode of CH2OO
(cm-1)
Δ𝐴−Δ 𝐵 IR
-0.019(5) MW
(19)
spacing/ cm-1
Δ(K2)
Nakajima et al., Chem. Phys. Lett. 621, 129 (2015)
c-type → Perpendicular band of prolate
Expt cm-1 QQ
Expt. 1 cm-1
Δ𝜈= Δ𝐴−Δ𝐵 Δ(𝐾 2 )+2 𝐴 ′ − 𝐵 ′
ν8 : cm-1

8. ν3, ν4, and ν6 modes of CH2OO ν3 ν4 ν6 in cm-1 ν0 1434.1 1285.9 909.26
CH2 scissor/ C=O str. (ν3)
a:b = 0.99:0.01
C=O str./CH2 scissor (ν4)
a:b=0.88:0.12
O-O stretching (ν6)
a:b = 0.98:0.02
in cm-1 ν3 ν4 ν6 ν0
1434.1
1285.9
909.26
Δ𝐴−Δ 𝐵
0.010(3)
0.0003(2)
-0.014(2)
Δ 𝐵 -
(3)
(5)

9. ν5 mode of CH2OO A’ 1241 cm-1 a-type:b-type = 60:40 A 1241 cm-1
CH2 rocking (ν5)
a-type:b-type = 0.53:0.47 A’
a-type:b-type = 60:40
1241 cm-1 A
1241 cm-1
ν5 : cm-1 ν4

10. Assignment for band A
Comparison of observed spectrum with simulated spectrum (0.25 cm-1)
1234 cm-1
Li et al., J. Phys. Chem. Lett. 5, 2364 (2014)

11. 2ν9 mode of CH2OO A”sym  c- type A’sym  a- or b- type
CH2 twist (ν9)
c-type
J. Chem. Phys. 142, (2015)
A”sym  c- type
A’sym  a- or b- type
2ν9 : cm-1
ν5 : cm-1 ν4

12. Importance of ICH2OO CH2OO + I CH2I + O2 → ICH2OO* ICH2OO
Proposed mechanism
UV VIS Spectrum
ICH2OO
J. Sehested et al., Int. J. Chem. Kinet. 26, 259 (1994)
T. Gravestock et al., ChemPhysChem 11, 3928 (2010)
CH2I + O2 → ICH2OO*
CH2OO + I
ICH2OO M
decompose
(for P < 60 torr)
(CH2OO?)
(CH2OO ?)
CH2OO
Beames et al., J. Am. Chem. Soc. 134, (2012)
Sheps, J. Phys. Chem. Lett. 4, 4201 (2013)
Ting et al. Phys. Chem. Chem. Phys. 16, (2014)
Observation of gaseous ICH2OO:
spectral characterization
probe for kinetic measurements
Huang et al., J. Phys. Chem. Lett 3, 3399 (2012)
Stone et al., Phys. Chem. Chem. Phys. 15, (2013)
Ting et al., J. Chem. Phys. 141, (2014)

13. CH2I2/N2/O2 + 308 nm under different PN2
CH2I + O2 + M→ ICH2OO + M
1-7 μs, R = 1 cm-1
Pt = 102 torr
Pt = 206 torr
Pt = 303 torr
Pt = 403 torr

14. Observed spectra of ICH2OO
CH2I2/O2/N2 nm
average 12 spectra
syn-ICH2OO
anti-ICH2OO
P (anti-ICH2OO) = 13 %
d (ICOO) = -87.6
d (HCOO) = 31.7
Δ E = 0 kJ mol-1
d (ICOO) = 180
d (HCOO) = 62.0
Δ E = 3.8 kJ mol-1
0.5 cm-1
avg. 13
0.5 cm-1
CH2I2
NEVPT2/aVDZ
B3LYP/aug-cc-pVTZ-pp

15. ν4 - ν6 modes of syn-ICH2OO CH2 wag (ν4) CH2 twist (ν5) C-O str. (ν7)
torsional (ν12)
76 cm-1 (theo.)
O-O str. (ν6)
B3LYP/aug-cc-pVTZ-pp

16. [CH2OO] + [ICH2OO] = const.16
Yield of CH2OO vs. ICH2OO
ICI
IOO
1-7 μs
ICH 2 OO CH 2 OO = I OO I CI ÷ ε OO 𝜀 CI
[CH2OO] + [ICH2OO] = const.
slope = 1.10 ± 0.21
𝜀 𝑂𝑂 𝜀 𝐶𝐼 →
slope of IOO vs. ICI

17. [CH2OO] + [ICH2OO] = const.17
Yield of CH2OO vs. ICH2OO
yCI = CH 2 OO CH 2 OO + ICH 2 OO + 𝑜𝑡ℎ𝑒𝑟𝑠
[CH2OO] + [ICH2OO] = const.
yCI-1 ≈ ICH 2 OO CH 2 OO ≈ 1 + ( I OO I CI ÷ ε OO 𝜀 CI )
~15 % at 1 atm
~18 % at 1 atm
~30 % at 1 atm
yCI-1 = (1.04±0.02) + (9.7±0.3) ×10-20 [M]
Huang et al., JPC Lett. 3, 3399 (2012)
Stone et al., PCCP. 15, (2013)
Ting et al., JCP 141, (2014)

18. Summary 1. IR spectrum of CH2OO at R= 0.25 cm-1
correct assignments of 2ν9 and ν5
spectral parameters of vib. excited states and band origins
CH2OO ν3 ν4 ν5 ν6 ν8
2ν9
Expt. ν0
1434.1
(24)
1285.9
(37)
1213.3
(8)
909.26
(100)
847.44
(17)
1234.2
(27)
Theo. ν0
1433.7
(38)
1285.4
(70)
1211.7
(11)
927.2
(129)
859.4
1233.9
(28)
Δ𝐴−Δ 𝐵
0.010(3)
0.0003(2)
0.005(3)
-0.014(2)
-0.019(5)
0.066(1)
Δ 𝐵 -
(3)
(5)

19. Summary 2. IR absorption spectrum of ICH2OO
assignments of ν4 –ν7 modes of syn-ICH2OO
hot bands involving ν12 are present in ν7 mode
ICH2OO ν4 ν5 ν6 ν7
CH2 wag
CH2 twist
O-O str.
C-O str.
Expt.
1233.8
(41)
1224
(17)
1087
(19)
923.0
(37)
p-H2 Matrix
1231.8
1225.6/
1085.6
917.7
(46)
Theo.
1220
(36)
1227
(10)
1100
(16)
897
Y.-F. Lee and Y.-P. Lee, Mol. Phys. accepted (2015)

20. Summary 3. Pressure dependence of the yield of CH2OO
Yield is derived from the observed spectra of CH2OO and ICH2OO
yCI-1 = (1.04±0.02) + (9.7±0.3) ×10-20 [M]
~30 % of CH2OO at 1 atm

21. Thanks for your attention!
Acknowledements:
Prof. Yuan-Pern Lee
Kuo-Hsiang Hsu, Yu-Te Su, Hui-Yu Lin, and Li-Wei Chen
Ministry of Science and Education of Taiwan
Ministry of Education $
Thanks for your attention!

23. CH2I2/N2/O2 photolysis at 308 nm / 248 nm at different Pt
0.5 cm-1
0.25 cm-1
0.25 cm-1
0.25 cm-1

24. ν8 mode of syn-CH2BrOO Locate first 5 bands Assumptions
Population
884.90
1.00 1
883.00
0.67 2
881.40
0.46 3
879.90
0.33 4
878.40
0.24 5
877.1
0.18 6
875.9
0.14 7
874.9
0.11 8
874.0
0.10 9
873.2
0.08 10
872.6
0.07
torsion (ν12)
Locate first 5 bands
Assumptions
Rotational contour
IR intensity
Boltzmann distributions
Peak positions

25. ICH2OO simulation CH2 wag (ν4) a: b: c = 0.81: 0.12: 0.07
CH2 twist (ν5)
a: b: c = 0.09: 0.54: 0.37

26. ν12 = 76 cm-1 torsion (ν12) C-O str. (ν7) a: b = 0.99: 0.01 ν 923.0
Population
923.0
1.00 1
921.3
0.73 2
919.6
0.53 3
918.0
0.39 4
916.5
0.29 5
915.1
0.22 6
913.7
0.16 7
912.4
0.12 8
911.2
0.10 9
910.0
0.07
O-O str. (ν6)
a: b: c = 0.83: 0.03: 0.14

27. Pt= 557 torr PTotal PO2 PN2 /atm /Torr 0.733 0.026 16.0 540.8
-Δ[CH2I2]
PO2
PN2
/atm
/Torr
0.733
0.026
16.0
540.8