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

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)

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, 11883 (2008) Welz et al., Science 335, 204 (2012)

Experimental setup

Absorption spectrum at 0.25 cm-1 resolution CH2I2/N2/O2 (0.13/2.77/97.12)@248 nm, Pt = 94 torr 1 cm-1 ν6 0-12.5 μs ν4 ν8 ν3 ν5 average 13 spectra 0.25 cm-1 0-25 μs Su et al., Science 340, 174 (2013)

Spectral analysis: near prolate approximation b 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, 101103 (2013) VCI-5 and B3LYP/aug-cc-pVTZ J. Chem. Phys. 142, 214301 (2015)

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 -0.017 19676(19) spacing/ cm-1 Δ(K2) Nakajima et al., Chem. Phys. Lett. 621, 129 (2015) c-type → Perpendicular band of prolate Expt. 0.25 cm-1 QQ Expt. 1 cm-1 Δ𝜈= Δ𝐴−Δ𝐵 Δ(𝐾 2 )+2 𝐴 ′ − 𝐵 ′ ν8 : 847.44 cm-1

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 - -0.0002(3) -0.0030(5)

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 : 1213.3 cm-1 ν4

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)

2ν9 mode of CH2OO A”sym  c- type A’sym  a- or b- type CH2 twist (ν9) c-type J. Chem. Phys. 142, 214301 (2015) A”sym  c- type A’sym  a- or b- type 2ν9 : 1234.2 cm-1 ν5 : 1213.3 cm-1 ν4

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, 20045 (2012) Sheps, J. Phys. Chem. Lett. 4, 4201 (2013) Ting et al. Phys. Chem. Chem. Phys. 16, 10438 (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, 19119 (2013) Ting et al., J. Chem. Phys. 141, 104308 (2014)

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

Observed spectra of ICH2OO CH2I2/O2/N2 (0.06/16/94)@308 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

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

[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

[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 ≈ 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, 19119 (2013) Ting et al., JCP 141, 104308 (2014)

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 - -0.0002(3) -0.0030(5)

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/ 1226.5 1085.6 917.7 (46) Theo. 1220 (36) 1227 (10) 1100 (16) 897 Y.-F. Lee and Y.-P. Lee, Mol. Phys. accepted (2015)

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

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!

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

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

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

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

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