New high resolution spectroscopy studies of methyl nitrite CH3ONO

Vincent Sironneau, P. Chelin, F. KwabiaTchana, I. Kleiner, J. Orphal, O. Pirali, J.-C. Guillemin, L. Margulès, R. Motiyenko, S. Cooke, W.J. Youngblood, A. Agnew, C.T. Dewberry

Columbus 2010

Atmospheric interests

Produced by biomass burning Involved in the photochemical oxidation of volatile organic

compounds Rapid photolysis

Lifetime in the atmosphere? (2 minutes*) Detection?

*W.D. Taylor, T.D. Allston, M.J. Moscato, G.B. Fazekas, R.Kozlowski, G.A. Takacs, Int. J. Chem. Kinet. 12 (1980) 231–240.

Fundamental interest

Energy difference between the two isomers is approximately 275cm-1

cis-trans barrier height: 3786 cm-1 Internal rotation potential barrier:

cis isomer : 739 cm-1

trans isomer : 15 cm-1

Most studies concern cis-trans interconversion, photofragmentation, UV absorption spectrum

cis-methyl nitrite trans-methyl nitrite

J.B.P. da Silva, N.B. da Costa, M.N. Ramos, R. Fausto, J. Mol. Struct. 375 (1996) 153-180B. J. van der Veken, R. Maas, G. A. Guirgis, H. D. Stidham, T. G. Sheehan, J. D. Durig, J. Phys. Chem. 94 (1990) 4029-4039A. Untch, R. Schinke, R. Cotting, J.R. Huber, J. Chem. Phys. 99 (1993) 9553-9556H.-M. Yin, J.-L. Sun, Y.-M. Li, K.-L. Han, G.-Z. He, S.-L. Cong, J. Chem. Phys. 118 (2003) 8248-8255

Difficulties for the MW and IR analysis

Two isomers Internal rotation of the methyl group Hyperfine structure (quadrupole of

nitrogen) Low vibrational modes Very weak torsional bands, not observed

with standard sources Not commercial

Internal rotation of the methyl group in CH3ONO

Cis isomer: the barrier V3 = 739 cm-1

Example for the 150,15-150,15 line

vt = 0 the A and E lines separated

by 60 kHz vt = 1 the splitting E-A is 3.6 MHz

The splitting depends of the height of the barrier the higher the barrier is, the smaller the splittings are

Trans isomer: the barrier V3 = 15 cm-1

free rotor, quantum number “m” for the torsional state 872 MHz for the 202-101 transition

Some low barrier molecules studied so far : acetamide, V3 = 25 cm-1 (JMS 2004) para-tolualdehyde V3 = 28 cm-1 Grabow et al WH07 meta-tolualdehyde V3 = 35 cm-1, K. M. Hotopp

D. S. Wilcox, A. J. Shirar, B. C. Dian, TC12, RH15 trans-methyl formate V3 = 15 cm-1,Muckle et al,

Columbus 2009

Previous MW studies Lines available in the literature for the cis:

60 lines for vt = 0 (J ≤ 20) 20 lines for vt = 1 (J ≤ 3) 20 for vt = 2 (J ≤ 3) measurements/assignments errors: bad do-loops in vt=1

A few lines (about 30) for the trans J < 5

P.N. Ghosh, A. Bauder, H.H. Günthard, Chem. Phys. 53 (1980) 39–50P.H. Turner, M.J. Corkill, A.P. Cox, J. Phys. Chem. 83 (1979) 1473-1482L. M. Goss, C. D. Mortensen and T. A. Blake, J. Mol. Spectrosc., 225, 182-188 (2004)

Previous IR studies Infrared spectra at low resolution of CH3ONO and

CD3ONO (1982) Only one study at high resolution ν8 cis-CH3ONO (2004)

Presents analysis Presently the analysis deals only with the

cis-CH3ONO First part:

New microwave measurements Between 1 and 21 GHz, S. Cooke, W.J. Youngblood, A. Agnew, C.T. Dewberry, University of North Texas (TC04) Between 75 and 465 GHz, L. Margulès, R. Motiyenko, Phlam Lille

FIR in the French Synchrotron Soleil, V. Sironneau,

P. Chelin, F. Kwabia Tchana, I. Kleiner, J. Orphal, O. Pirali, J.-C. Guillemin

Second part: MIR region at LISA Créteil, V. Sironneau, P. Chelin, F. Kwabia

Tchana, I. Kleiner, J.-C. Guillemin

Microwave measurements at Phlam, Lille (75-93GHz, 150-235GHz and

398-465GHz) 6≤J≤40

Laurent Margulès and Roman Motiyenko

Cis isomer:vt=2n14 ~ 213 cm-1

n10 ~ 346 cm-1

vtors ~ 170 cm-1? (previous MW studies)vtors ~ 214 cm-1 (this work)

Trans isomers:vt=0, vt=1n14 ~ 230 cm-1? n10 ~ 379 cm-1 vtors ~ 26 cm-1?(E) and 80 cm-1?(A)

Results Fit done with the Belgi-Cs

program All parameters are in the

Rho Axis Method Values in cm-1 except ρ

which is unitless Number of lines

707 for vt=0 715 for vt=1 1 ≤ J ≤ 40 0 ≤ Ka ≤ 23

31 parameters 34kHz close to the

experimental accuracy

J. T. Hougen, I. Kleiner, and M. Godefroid, J. Mol. Spectrosc. 163 (1994) 559-586

nlma Operator Parameterb values220 (1/2)(1-cos3γ) V3  739(3)

Pγ² F 6.183(18)211 PγPa ρ 0.0861038(82)202 Pa

2 ARAM 0.591655(15)Pb

2 BRAM 0.332055(13)Pc

2 CRAM 0.1882082(31)(PaPb+PbPa) Dab 0.16835(1)

440 Pγ4 k4 -0.405(13) ×10-3

(1/2)(1-cos6γ) V6 76.26(41)422 Pγ² Pa

2 Gv -0.5245(73) ×10-4

sin3γ (PbPc+PcPb) Dbc 0.001352(85)(1-cos3γ)Pa

2 k5 0.013938(31) (1-cos3γ)P2 Fv -0.00878(7)

422 (1-cos3γ) (PaPb+PbPa) dab 0.010475(12)2 Pγ²(Pb

2-Pc2) c1 -0.251(10) ×10-5

413 Pγ Pa P2 Lv 0.955(16) ×10-5

Pγ Pa3 k1 0.722(27) ×10-5

Pγ{Pa(Pb2-Pc

2)} c4 0.1877(82) ×10-5

404 - P4 ΔJ 0.2613(30) ×10-6

- P2Pa2 ΔJK -0.30(35) ×10-7

- Pa4 ΔK 0.210(69) ×10-5

- 2P2(Pb2-Pc

2) δJ 0.855(15) ×10-7

- {Pa2,(Pb

2-Pc2)} δK 0.378(13) ×10-6

P2(PaPb+PbPa) DabJ 0.103(12) ×10-6

Pa2(PaPb+PbPa) DabK -0.10357(8) ×10-5

606 - {Pa2,(Pb

2-Pc2)} φK 0.39(2) ×10-11

642 (1-cos6γ)P2 NV 0.002719(44)Pγ

4 P2 MV -0.457(10) ×10-7

Pγ4(Pb

2-Pc2) c3 0.1856(69) ×10-7

624 (1-cos3γ) P2(PaPb+PbPa) dabJ -0.401(11) ×10-8

(1-cos3γ) Pa2(PaPb+PbPa) dabK -0.429(28) ×10-7

FIR spectrum of methyl nitrite at the French Synchrotron Soleil

O.Pirali, V. Sironneau, P. Chelin,J. Orphal

Goals:- Very weak torsional bands

150cm-1 (hot band progressions)170cm-1 (previous MW studies)214cm-1 (our study)

- High J and Ka values in the pure rotational spectrum

Pure rotational spectrum of CH3ONO recorded at the French Synchrotron Soleil

Pure rotational spectrum of cis-CH3ONO in the FIR region (15-65cm-

1)

P = 0.11 mbar, L = 150 m Res = 0.0011cm-1

No resolved internal rotor splittings in the FIR for the cis-isomer

Waston type Hamiltonian in A reduction, Ir representation (Maki’s code)

Ghosh et al.[2] Goss et al. [14] This work

A 0.6762191(120) 0.6762192(16) 0.67621038(34)

B 0.2481020(1) 0.2481021(5) 0.24809892(21)

C 0.1878160(3) 0.1878163(5) 0.18781343(24)

ΔJ 2.25E-07(7) 2.2407E-07(76) 2.23938E-07(67)

ΔJK -4.30E-07(43) -5.11E-07(69) -5.1759E-07(25)

ΔK 1.834E-06(70) 1.892E-06(17) 1.89466E-06(33)

δJ 7.0E-08(3) 6.654E-08(50) 6.7014E-08(11)

δK 1.8E-07(7) 2.42E-07(20) 2.4237E-07(34)

ΦJ -1.45E-13(6)

ΦJK 8.37E-13(45)

ΦKJ -1.09E-11(1)

ΦK 2.569E-11(9)

rms 110kHz 0.00044 0.00012

N.of lines 31 MW 32 MW+ 634 IR 2164 IR

J range 0-18 4-47 12-81

Ka range 0-7 0-17 0-48

Values in cm-1

Infrared Spectra at LISA, Créteil

resolution of 0.0019cm-1 P= 0.3 Torr, L=3.2m

resolution of 0.003cm-1 P=0.05 Torr, L=19.2m

ν8 band of cis-methyl nitrite

Goss et al. Watson type Hamiltonian (634 lines) rms = 0.00044cm-1

But splittings for the low values of J and Ka and they are not included in their fit

With BELGI-Cs (708 + 118 internal rotor splittings lines) rms = 0.00048cm-1 (2 ≤ J ≤ 50, 0 ≤ Ka ≤ 22)

But V3= 623cm-1 (739cm-1 for the ground state) and F = 6.82cm-1 (6.18cm-1 for the ground state) effectives valuesP.N. Ghosh, H.H. Gunthard, Spectrochim. Acta 37A (1981) 347–363

L. M. Goss, C. D. Mortensen and T. A. Blake, J. Mol. Spectrosc., 225 (2004) 182-188

ν9 band of cis-methyl nitrite

Around 650 assigned lines with a rms 0.00046cm-1

The internal rotor splittings are not included yet into the fit

Conclusions Microwave analysis of

the vt=0 and vt=1 for cis-CH3ONO (1422 lines rms = 34kHz

J up 1 to 40, BELGI code)

Global analysis MW+FIR presents status : 3482 lines 1422 MW (707 in vt=0 and 715 in vt=1)+ 2060 FIR ( 1342 in vt=0 and 718 in vt=1) rms = 35kHz , 0.00018cm-1

FIR pure rotational spectrum of cis-methyl nitrite (2164 lines

rms = 0.00012 cm-1 J = 12 up to 81, Maki’s

code)

Future work

Plan to search vt=2 for the cis-isomers (expected perturbations with ν14 and ν10)

Need MW data for low J and Ka value to start the study of trans-methyl nitrite…

Conclusions in the MIR

For the ν8 band, our effective model reproduce well the internal rotor splittings (Spectral range for an atmospheric detection?)

The analysis of the ν9 band is still in progress: vibration-rotation-torsion interactions need to be modeled!

Synthesis Solution 1: 11g of sodium

nitrite + 6,4g of methanol in 50mL of water

Solution 2: 8g of sulfuric acid + 14mL of water

Pour the solution 2 mL by mL in the first one

In 800-900mbar nitrogen atmosphere

Methanol is the principal impurity

Methyl nitrite was condensed in a trap at -80°C (pale yellow liquid)

In spite of several purifications (distillation) a trace of methanol was still present