1. Study of the CH 2 I + O 2 Reaction with a Step-scan Fourier-transform Infrared Absorption Spectrometer: Spectra of the Criegee Intermediate CH 2 OO and Dioxirane(?) 1 Yu-Hsuan Huang 1 and Yuan-Pern Lee 1, 2 1 Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, Taiwan 2 Institute of Atomic and Molecular Sciences, Academia Sinica, Taiwan 69 th International Symposium on Molecular Spectroscopy

2. 2 Importance of CH 2 OO 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) + + Decomposition of CH 2 OO Chen et al., J. Phys. Chem. A 106, 1877 (2002) (kcal/mol  1 ) stabilization Isomerization and decomposition HCOOH, OH, CH 3, CO, CO 2, etc (primary ozonide) (Criegee intermediate)

3. 3 Experimental observation of CH 2 OO Photoionization mass spectrometry Taatjes et al, J. Am. Chem. Soc. 130, 11883 (2008) Welz et al, Science 335, 204 (2012) Huang et al., J. Phys. Chem. Lett 3, 3399 (2012) Stone et al. Phys. Chem. Chem. Phys. 15, 19119 (2013) Proposed mechanism

4. 4 IR Identification of CH 2 OO Comparison of observed spectrum with simulated spectrum (1 cm -1 ) Su et al., Science 340, 174 (2013)

5. 5 Experimental setup

6. 6 Absorption spectrum at 0.25 cm -1 resolution 0-12.5 μ s 0-25 μ s 1 cm  1 0.25 cm  1 CH 2 I 2 /N 2 /O 2 (0.13/2.77/97.12)@248 nm, P t = 94 torr ν8ν8 ν6ν6 ν4ν4 ν3ν3 ν5ν5 Su et al., Science 340, 174 (2013)

7. 7 Spectral analysis: near prolate approximation a b c κ =  1 prolate κ =  1 oblate Parallel transitions Perpendicular transitions ΔJ = 0, Q branch ΔJ = 1, R branch ΔJ =  1, P branch Q branch a-type b-type & c-type Rotational constants of vibrational ground state M. Nakagima and Y. Endo, J. Chem. Phys. 139, 101103 (2013) CsCs

8. y = -0.023 x+ 4.33 Expt. 1 cm -1 8 Spectral analysis of ν 8 CH 2 wagging ( ν 8 ) c-type cm -1 ground ν8ν8 ν 847.3 A 2.593552.57862 B 0.415800.41475 C 0.357620.35807 Expt. 0.25 cm -1 Expt.-0.0232.17 simulation-0.0152.19

9. Expt. 1 cm -1 9 Spectral analysis of ν 6 O-O stretching ( ν 6 ) a-type:b-type = 0.98:0.02 9 Δ B < 0 Δ A  Δ B <0, from Q cm -1 ground ν6ν6 ν 909.2 A 2.593552.57880 B 0.415800.41330 C 0.357620.35539 Expt. 0.25 cm -1

10. 10 Simulation of ν 3 and ν 4 CH 2 scissor/ C=O str. ( ν 3 ) a-type:b-type = 0.99:0.01 cm -1 ground ν3ν3 ν4ν4 ν 1434.11285.7 A 2.593552.599762.5954 B 0.415800.415040.4190 C 0.357620.356580.3540 C=O str./CH 2 scissor ( ν 4 ) a-type:b-type=0.88:0.12

11. Expt. 1 cm -1 11 Simulation of ν 5 CH 2 rocking ( ν 5 ) a-type:b-type = 0.53:0.47 cm  1 ground ν5ν5 ν 1241 A 2.593552.61000 B 0.415800.41641 C 0.357620.35627 Expt. 0.25 cm -1

12. 12 P t = 102 torr P t = 206 torr P t = 303 torr CH 2 I 2 /N 2 /O 2 + 308 nm under different P N2 1-7 μs, R = 1cm -1 P t = 403 torr

13. Observed spectra of CH 2 IOO and simulations CH 2 I 2 /O 2 /N 2 (0.06/16/94)@308 nm, P t = 300 torr CH 2 OO ν 4 CH 2 IOO ν 4 = 1233.6 cm -1 CH 2 IOO ν 5 = 1228 cm -1 13

14. Expt. 1 cm -1 14 Simulation of ν 5 CH 2 rocking ( ν 5 ) a-type:b-type = 0.53:0.47 Expt. 0.25 cm -1 1213 cm -1 CH 2 IOO : ν 4 = 1233.6 cm -1, ν 5 =1228 cm -1 Simulation ν 5 of CH 2 OO ?

15. 15 Identification of Dioxirane ? Comparison of observed spectrum with simulated spectrum (0.25 cm -1 )

16. 16 cm -1 ground ν3ν3 ν7ν7 ν dioxirane1231.51213.2 A 0.966570.97150.9605 B 0.835780.83720.8302 C 0.493010.49450.4966 C-O sym. str. ( ν 3 ) b-type CH 2 rock ( ν 7 ) c-type Suenram and Lovas, J. Am. Chem. Soc. 100, 5117 (1978) Dioxirane: ν 3 and ν 7 ν 5 of CH 2 OO : 1230.7 cm -1

17. 17 cm -1 ground ν3ν3 ν7ν7 ν dioxirane1231.51213.2 A 0.966570.97150.9605 B 0.835780.83720.8302 C 0.493010.49450.4966 C-O sym. str. ( ν 3 ) b-type CH 2 rock ( ν 7 ) c-type Dioxirane: ν 3 and ν 7 Suenram and Lovas, J. Am. Chem. Soc. 100, 5117 (1978)

18. 18 cm -1 ground ν9ν9 ν dioxirane899.8 A 0.966570.95956 B 0.835780.83700 C 0.493010.50264 C-O asym. str. ( ν 9 ) a-type Dioxirane: ν 9 Suenram and Lovas, J. Am. Chem. Soc. 100, 5117 (1978)

19. 1. High resolution IR spectrum of CH 2 OO definative assignment of ν 3, ν 4, ν 6 and ν 8 ν 5 was misassigned band origins of ν 3, ν 4, ν 6 and ν 8 are determined 19 Summary CH 2 OO ν3ν3 ν4ν4 ν5ν5 ν6ν6 ν8ν8 Expt.1434.1(15)1285.7(32)1230.7(8)909.2(100)847.3(12) Theo.1458(31)1302(16)1220(18)892(106)853(30)

20. 20 Summary 2. IR absorption spectrum of CH 2 IOO overlapped bands of ν 4 / ν 5 and ν 7 (overlapped with CH 2 OO) yield increases with pressure CH 2 IOO ν4ν4 ν5ν5 ν7ν7 Expt.1233.6(27)1228(6)919(13) p-H 2 Matrix1231.8(53)1225.6/1226.5(19)917.7(50) Theo.1235(28)1231(35)901.4(50)

21. 21 Summary 3. Possible observation of Dioxirane Dioxirane ν3ν3 ν7ν7 ν9ν9 Expt.1231.5(23)1213.2(2)899.8(10) Theo.1238(48)1149(7)911(26) 2. IR absorption spectrum of CH 2 IOO CH 2 IOO ν4ν4 ν5ν5 ν7ν7 Expt.1233.6(27)1228(6)919(13) p-H 2 Matrix1231.8(53)1225.6/1226.5(19)917.7(50) Theo.1235(28)1231(35)901.4(50)

22. 22 Thanks for your attention! Acknowledements: Prof. Yuan-Pern Lee Kuo-Hsiang Hsu, Yu-Te Su, and all the group members National Science Council of Taiwan and the Ministry of Education

23. 23

24. 24 P t = 102 torr P t = 206 torr P t = 303 torr P t = 403 torr Subtracted spectra: spectra of CH 2 IOO P O2 ~ 16 torr, P CH2I2 ~ 0.14~0.18 torr 343 K R = 1 cm -1 P O2 ~ 16 torr, P CH2I2 ~ 0.14~0.18 torr 343 K R = 1 cm -1 Integrated 1-7 μs 1-7 μs, R = 1cm -1

25. 25 Observed spectra of CH 2 IOO and simulations PO2 ~ 16 torr, PCH2I2 ~ 0.14~0.18 torr 343 K R = 1 cm-1 Integrated 1-7 μs Simulation: freq. and intensity from p-H 2 matrix rot. const. all from B3LYP ν 0 and relative intensity adopted from spectra in p-H 2 matrix

26. 26 Observed spectra of CH 2 IOO and simulations CH 2 I 2 /O 2 /N 2 (0.06/16/94)@308 nm, P t = 300 torr

27. 27 ν 7 ν C-O /  CH2 ν 6 ν O-O /  CH2 ν 3  CH2 ν 4  CH2 ν 5  CH2 ν 8  CH2 Mode description p-H 2 matrix COO deform.490.2 C-I str.550.5 CH 2 wag.841.6/841.1 C-O917.7 O-O1085.6 CH 2 torsion1225.6/1226.5 CH 2 rock1231.8 CH 2 sci.1408.9 CH 2 str.2982.4 ν: stretch, δ: bend or deformation, δ s : scissor, ω: wag, ρ: rock, τ: torsion

28. 28 Observed spectra of CH 2 OO and simulations CH2OOυ(0.25 cm-1)Normalize ν41285.732 ν51230.78 dioxiraneυ(0.25 cm-1) ν31231.523 ν71213.22 CH2IOOυ(0.25 cm-1) ν41233.65 ν512281 CH2OOυ(0.5 cm-1)Normalize ν41285.732 ν51230.78 dioxiraneυ(0.5 cm-1) ν31231.515 ν71213.21 CH2IOOυ(0.5 cm-1) ν41233.627 ν512286

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30. 30

31. Expt. 1 cm -1 31 Spectroscopic analysis of ν 6 O-O stretching ( ν 6 ) a-type:b-type = 0.98:0.02 31 Δ B < 0 Δ A  Δ B <0, from Q cm -1 ground ν6ν6 ν 909.2 A 2.593552.57880 B 0.415800.41330 C 0.357620.35539 Expt. 0.25 cm -1