Stéphane Bailleux stephane.bailleux@univ-lille1.fr University of Lille Fourier–transform microwave and millimeter–wave spectroscopy of CH2IBr (v = 0) Stéphane Bailleux stephane.bailleux@univ-lille1.fr University of Lille June 17, 2014　– 69th ISMS Meeting

Spectroscopy of CH2 XY species X , Y = { F, Cl, Br } : extensive studies X = I CH2I2 : Z. Kisiel et al. (1996) CH2IF : C. Puzzarini et al. (2011) CH2ICl : S. Bailleux et al. (2011) CH2IBr : this work

Atmospheric chemistry of iodine A. Saiz–Lopez et al. Chem. Review. 2011 Aerosol I IO OIO IX I2, CH2I2, CH2IX, CH3I, … I, I2, IO, IO2: detected O3 loss -–– ℎn

Source of atmospheric iodine S. Archer et al. J. Geophys. Res. 2006 CH2 ICl 44% CH2 I2 22% CH3 I 23% CH2 IBr : 5% C2H5 I : 6% di-halogenated species are much more photolabile

Congested rotational spectra ! Complex hyperfine structure (quadrupole): quadrupolar and rotational constants : similar magnitudes small rotational constants and low frequency ICBr bending vibrational mode 2 Br isotopologues : 79Br : 81Br = 1 : 1 IBr = 3/2 ⇒ 24 hyperfine levels I I = 5/2

High level quantum chemical calculations Rotational constants (MP2) Centrifugal distortion constants, up to sextic (B3LYP) Quadrupolar coupling constants cij (a = I, Br) cij (a) = eQa /h qij(a) HeQq(a) = - ⅙ QI, Br : ∇EI, Br Dipole moments (D) µa = 0.09 µb = 1.54 b a Cs symetry k = -0.998 data not available in the literature

Predicted microwave spectra (b–type) search candidates MHz

Predicted microwave spectra 23000 23500 24000 24500 25000 25500 26000

Predicted microwave spectra 23000 23500 24000 24500 25000 25500 26000 low N, Q-branch transitions 111-000

111 – 000 transition assigned Predicted (B3LYP) Observed

111 – 000 transition after fitting A, B, C and N.Q.C.C. determined

Assignments of Q-branches CH2I79Br CH2I81Br

Examples of spectra NKaKc = 111 – 000 F1 = J + IBr F1 = F1 + I I CH2I81Br

79Br 81Br Results assigned (J  132 Ka  14) µw ( 23 – 25 GHz) : µb 428 439 mmw (120 – 243 GHz) : µa 009 0021 mmw (200 – 243 GHz): µb 0441 0519

Constants (MHz) of CH2 I 79Br observed MP2 6–311+G Rotation A 0024054.8910 26687 B 0000892.3920 00895 C 0000865.0090 00867 Iodine Coupling caa –1275.31 –1300 cbb 00236.38 00263 |cab| 01296.20 01278 Bromine Coupling 0304.38 00315 00+4.35 000–7 0418.01 00414 r0 structure electronic structure

Geometry HCH / ° ICX / ° XCH / ° CH2IF CH2ICl CH2I79Br CH2I2 re r0 rz C – I / Å 2.1410 2.1485 2.1434 2.134(2) C – X / Å 1.3584 1.7541 1.9147 C – H / Å 1.0841 1.0832 1.0817fixed 1.085 HCH / ° 112.45 107.93 107.86 111.27 ICX / ° 110.79 113.03 113.47 114.0(3) XCH / ° 109.95 112.16 111.80

Concluding remarks Organic iodine in the atmosphere: ozone depletion impact on the radiative balance our data (hopefully) … will prompt vibrational spectroscopic studies give the potential for atmospheric monitoring

Measurement & analysis Contributors Measurement & analysis Computations Toho University (MMW) K. Taniguchi S. Sakai H. Ozeki Shizuoka University (FTMW) T. Okabayashi Kean University W. Bailey Lille University D. Duflot acknowledgements French National Research Agency

Centrifugal distortion of CH2 I 79Br observed MP2 SDB-VTZ quartic (kHz) DJK 000.1336491 (37) 0.123 –8.82364 (11)0 –8.6100 DKJ 374.083 (12) 0001 374. 0001 103  d1 20000000 –7.12740 (55) 0 –6.4300 0 103  d2 20000000 –0.09268 (24) 0 –0.0753 sextic (mHz) HJK 000.03082 (13) 00.0283 001.027 (11)00 000.71300 HKJ 0–544.3 (16) 00000 0–498.0000000 20008. (204) 00000 19700.000000 103  h1 20000000 04.567 (32) 03.9800 103  h2 20000000 00.146 (25) 00.126 103  h3 20000000 00000.01155 fixed 000.0105

Quadrupolar tensors of CH2 I 79Br cxx / MHz –289.7496 (49) 981.0133 (39) cyy / MHz –308.7330 (17) 1038.9290 (18) czz / MHz 598.4826 (49) –2019.9423 (39) h 0.03170 0.0287 qza / °Hz 35.13000 29.88000

Millimeter-wave spectrometer (Toho)