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

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

3. 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

4. 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

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

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

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

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

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

10. J = 77  76 and 78  77 : observed Ka

11. Example : JKa,Kc = 751,75  741,74

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

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

14. 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

15. 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

17. 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

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

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

21. Quadrupolar tensors of CH2 I 79Br
cxx / MHz
– (49)
(39)
cyy / MHz
– (17)
(18)
czz / MHz
(49)
– (39) h
0.0287
qza / °Hz