Stéphane Bailleux stephane.bailleux@univ-lille1.fr Nitrosyl iodide, INO: millimeter-wave spectroscopy guided by ab initio quantum chemical computation Stéphane Bailleux stephane.bailleux@univ-lille1.fr June 26, 2015　– 70th ISMS Meeting

Content Introduction Results Prospects previous works atmospheric implication of INO Results computations observations Prospects

Contributors Lille University acknowledgements Toho University (MMW) Measurement Computations Toho University (MMW) S. Aiba H. Ozeki Lille University D. Duflot acknowledgements French National Research Agency

Spectroscopy of XNOy (y = 1 – 3) X = { F, Cl, Br } : extensive studies : theoretical and experimental (uv/vis ; I.R. ; mmw) for the whole family (y = 1 – 3) X = I matrix isolated INO (1977) and INO2 (1979) : IR spectra gas-phase INO, INO2 and INO3 : low-resolution (1 cm-1) FTIR spectra (1991) INO , hi-resolution spectroscopy : this work

Atmospheric iodine photochemistry Aerosol I INO2 I2, CH2I2, CH2IX, CH3I, … NO, XO IONO2 O3 loss Chem. Rev. 112 (2012), p. 1773 – Saiz-Lopez et al. : Atmospheric chemistry of iodine

Predicted rotational spectrum Quantum Chemistry Calculation MOLPRO 2012.1 CCSD(T) – F12b / cc–PVQZ–(PP) optimized structure (120 points grid) Geometry Dipole moments (D) : µa = 1.60 µb = 0.04 Cs symmetry k = -0.998 IN 2.356 Å NO 1.142 Å ∠INO 115.6 °

Computed rotational constants CCSD(T) / cc–PVQZ–(PP) Ae (MHz) 84030.8 Be (MHz) 2848.5 Ce (MHz) 2755.1 DJ (kHz) 1.67 DJK (kHz) -46.21 DK (kHz) 5 151 d1 (Hz) -70 d2 (Hz) -1.7

Hyperfine (quadrupolar) structure ⇒ 18 hyperfine sublevels I I = 5/2 Parameter (MHz) ANO / B3LYP Iodine coupling 3/2 caa -2160.025 1/4 (cbb - ccc ) 122.669 |cab| 615.917 Nitrogen coupling 0.461 -2.365 1.371 cij (a = N, I) : cij (a) = eQa /h qij(a) HeQq(a) = - ⅙ Qa : ∇Ea

Millimeter-wave spectrometer (Toho) Precursors : I2 + NO

J = 77  76 and 78  77 : observed Ka

Example : JKa,Kc = 751,75  741,74

frequency domain (/GHz) Results assignement 68 µa-type Ja 74 – 78 Ka 00 – 10 frequency domain (/GHz) 400 – 440 number of parameters 10

Rotational constants observed rms(fit) = 50 kHz A0aa 81797.4 (49)4444 CCSD(T) – F12b cc–PVQZ–(PP) A0aa 81797.4 (49)4444 84030.84 B0bb 2797.5464 (51) 2848.5 C0cc 12705.6691 (51) 2755.1 DJD 1.86305 (15) 001.67 DJKD -53.317 (47) -46.21 DKD 5890 (50)00000 5151000 d1DD -77.70(20)0 -7000 d2DD -1.915 (24) 0-1.7 HJHH HJKH 0000.0701 (42) HKJH -34.247 (80) HKHH (MHz) (kHz) (Hz) (Hz) rms(fit) = 50 kHz

Bond properties ∠XNO FNO ClNO BrNO INO re r0 rz X – N / Å 1.512 1.975 2.141 2.356 N – O / Å 1.136 1.139 1.147 1.142 ∠XNO 110°5’ 113°20’ 114°29’ 115°36’ contribution from ionic structures X-NO+ in nitrosyl halides: from 10% (FNO) to 40% (ClNOINO) NO+ NO r / Å 1.062 1.150

Concluding remarks First high-resolution rotational spectrum of INO will prompt vibrational spectroscopic studies give the potential for atmospheric monitoring hyperfine structure : remains to be observed Unidentified lines: IONO ? INOx trace species in the atmosphere: gaps in our understanding of I / NOx interaction (gas and aerosols) impact on ozone levels

INO vibrational frequencies Mode (cm-1) CCSD(T) / cc–PVQZ–(PP) FTIR gas-phase Ar matrix n1 (NO stretch) 1781.4 1785 1809 n2 (bend)00000 493.6 470 n3 (IN stretch)0 233.4 216

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

Computed hyperfine constants (MHz) observed CCSD(T) – F12b cc–PVQZ–(PP) Iodine caa -1440.0200 cbb 965.35 |cab| 615.92 Nitrogen 00.307 -4.884 01.371

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