Transcript FCO2n.ppt

Analysis of the n2 band of FCO2 radical,
O
preliminary results F  C O
A. Perrina, M. Strizikc,d , H. Beckersb, H. Willnerb
, Z.Zelingerc,d, P. Pracnae,
V. Nevrlyc,d, E. Grigorovac,d,
aLaboratoire
Interuniversitaire des Systèmes Atmosphériques (LISA)
CNRS Univ Paris Est & 7, Créteil cedex, France
bFB C—Anorganische Chemie, Bergische Universität Wuppertal, Gaußstrasse 20,
D-42097 Wuppertal, Germany
c VSB - Technical University of Ostrava, Czech Republic
dInstitute of Thermomechanics, vvi, Academy of Sciences of the Czech Republic, Prague,
Czech Republic
eJ.Heyrovsky Institute of Physical Chemistry, Academy of Sciences of the Czech Republic,
Prague, Czech Republic
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Stratospheric interest
• Studies concerning with the decrease of ozone in the
stratosphere were mainly restricted to reactions where Cl
and Br played the principal role
• The chemistry of other fragments formed by the
photolysis of the CFCs remained almost unexplored
• It is necessary to study oxidation and general
degradation mechanisms for various CFCs and HCFCs
• FCO2 radical has been postulated as an important
intermediate in the photo-oxidation of carbonyl difluoride,
COF2
Francisco, Goldstein Chem Phys 1988)
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Existing studies: very few…
• FCO2 was the subject of ab initio calculations
[Schneider, 1995, Breidung 2006]
• Rotational, spin-rotation & hyperfine structure
investigated by microwave and millimeter wave studies
[Kolesniková, 2008, Zelinger 2007].
• Visible spectrum B2A1X2B2 [Maricq 1993, Sncheider
1995].
• FCO2 radical isolated in noble gas matrices by electron
paramagnetic resonance spectroscopy [Beckers 2008]
and by infrared and UV spectroscopies [Argüello, 1995].
However the infrared spectrum of this radical is not yet well
known.
(See the references at the end of this presentation)
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Experimental details (Wuppertal)
• FCO2 was generated by vacuum flash pyrolysis
of bis- fluorocarbonylperoxide FCOOOCOF. This
was prepared in a flow system according to the
literature procedure [Russo et al, 1995] and
purified by trap-to-trap distillation.
• Fourier transform spectra (FTIR Bruker)
recorded in Wuppertal (800-1000 cm-1)
Complicated, …dangerous: …for
details…..ask to H. Beckers, H. Willner
from Wuppertal
Beckers, Willner, Grote, Sander, & Geier, J. Chem Phys. 128, 224301 2008
Russo and DesMarteau, Inorg. Chem. 34, 6221 1995.
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Relative to the exchange of the two oxygen nuclei
the total wave function: (Elect. Vibr. Rot. Nucl-Spin) must be symmetrical
In the ground
vibrational
state, only
Ka=odd levels
exist
This work
S. Bailleux, Z. Zelinger H. Beckers, and H. Willner
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The n2 band is an A type band (Ev=970.2085 cm-1)
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Analysis of the n2 band
• In the P- and R branches, the lines are grouped in
clusters corresponding to (2J’-K’c)=constant values.
• These P- and R- clusters are separated by ~0.4 cm-1
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In the R-branch: exemple of two clusters of lines
corresponding to (2J’-K’c)=constant values.
Only the Ka=odd values are
existing (symmetry reasons
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Analysis of the n2 band
• In the P- and R branches, the lines are grouped in
clusters corresponding to (2J’-K’c)=constant values.
• These P- and R- clusters are separated by ~0.4 cm-1
• Hyperfine structure not observable
• Electronic spin-rotation interaction effects are
observable.
• HSpin-Rot= eaa, NaSa+ebb NbSb+ecc NcSc+…
• The spin doublets are difficult to identify except for high
Ka values because the values of the eaa, ebb ecc in the
ground and in the 21 states are almost equal
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HSpin-Rot= eaa, NaSa+ebb NbSb+ecc NcSc+…
Spin-rotation
(in 10-3 cm-1)
Ground 21
eaa= -2.78 -2.78
ebb=-26.5 -27.3
ecc=-2.78 -1.31
.different for the n4
band : 1090 cm-1
Bailleux, Zelinger
Beckers, & Willner
Spin-rotation
(in 10-3 cm-1)
Ground
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eaa= -2.78
-5.90
ebb=-26.5
-47.3
ecc=-2.78
-15.8
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Analysis of the n2 band
• Starting from J=30 there is a Fermi
type resonance coupling the 21 52
energy levels (E55=964.15 cm-1 ,
E2=972.2 cm-1)
• This resonance was also observed by
matrix studies (G.A. Argüello, J.H. Grothe, M.Kronberg, and
H.Willner, H-G Mack,« IR and Visible Absorption Spectrum of the Fluoroformyloxyl
Radical, FCO2, Isolated in Inert Gas Matrices », J. Phys. Chem. 1995,99, 1752517531)
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Evidence of the 21  52 Fermi resonance …..
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Hamiltonian matrix
n2
J=N+1/2
n2
2n5
N
N+1
N
N+1
2n5
N
N+1
N
N+1
W+SR SR
F
SR W+SR
F
F
W+SR SR
F
SR W+SR
W= Watson type rotational Hamiltonian
SR: Spin Rotational operator
F: Fermi type operator
Fermi resonance
coupling 2152
21: Ev=970.15 cm-1
W=Ev+ A Nz2 + B Nx2+CNy2+…
SR= eaa SzNz+ebbSxNx+eccSyNy
F= F0+ F1{Nx2-Ny2}+F2 N2+F3Nz2
52: Ev=964.15 cm-1
already pointed out by
matrix studies
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Arguello, Grothe, Kronberg, Willner Mack, J.Phys Chem (1995) 99 17525
Results of the analysis
• We used the ground state parameters reported in
Kolesniková et al (2008).
• More than 2200 lines were identified leading to the
measurements of 1070 spin-rotation energy levels
• J 55, Ka 35
• Satisfactorily results were achieved low J values.
Difficulties arised for the assignments and the
calculations for J35.
Kolesniková, Varga,Beckers, Šimečková,Zelinger, Stříteská,
Kania,Willner and Urban, J. Chem Phys. 128, 224302 2008
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For the very high N values, the results are still not completely satisfactory
Several possible explanations:
-Errors in the assignments (still possible !!)
-Additional resonance (for example 5131 21 C-type resonance ???
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Conclusion
• The first analysis of the n2 band of FCO2 was
performed
• This analysis is complicated due to the nature of
the structure of this A-type band.
• A first calculation of the 21 spin-rotation energy
levels was performed. The theoretical model
accounts for both the spin rotation couplings
within the 21 vibrational state together with the
Fermi resonance coupling the 21 and 52 energy
levels.
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References
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•
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G.A. Argüello, J.H. Grothe, M.Kronberg, and H.Willner, H-G Mack,« IR and Visible Absorption
Spectrum of the Fluoroformyloxyl Radical, FCO2, Isolated in Inert Gas Matrices », J. Phys. Chem.
1995,99, 17525-17531
H. Beckers, H. Willner, D. Grote, W. Sander, and J. Geier, « Electron paramagnetic resonance
spectrum of the FCO2 radical isolated in noble gas matrices », J. Chem Phys. 128, 224301 2008
L. Kolesniková, J. Varga, H. Beckers, M. Šimečková, Z. Zelinger, L. Nová Stříteská, P.Kania,
H.Willner, and S.Urban, « Detailed study of fine and hyperfine structures in rotational spectra of
the free fluoroformyloxyl radical FCO2 »J. Chem Phys 128, 224302 2008
Z.Zelinger ,S. Bailleux, D. Babankova, M. Šimečková, L.N. Stříteska, L. Kolesnikova, P. Musil , P.
Kania, S.Urban, H. Beckers, H. Willner, High resolution rotational spectrum of FCO2 radical
(extension to lower frequencies) », J.Mol. Spectrosc. 243 (2007) 292–295.
W. F. Schneider, M. M. Maricq, J. J. Szente, and J. S. Francisco, J. Chem. Phys. 103, 6601 1995.
J. Breidung and W. Thiel, J. Phys. Chem. A 110, 1575 2006.
S. Bailleux, E.Grigorava, Z.Zelinger, H.Beckers, H. Willner, Analysis of the Fourier –transform
infrared spectrum of the n4 band of the fluoroformyloxyl radical, FCO2, in the X2B2 state, poster
J28 Praha 2008 , 20th International Conference on High Resolution Molecular Spectroscopy,
Praha 2008
A. Russo and D. D. DesMarteau, Inorg. Chem. 34, 6221 1995.
W. Gombler and H. Willner, J. Phys. E 20, 1286 1987.
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Structure
O
F  C O
re(CF) = 132.5(2) pm, re(CO) = 116.7(2) pm, & θe(FCO)
= 127.8(2)°.
Jürgen Breidung and Walter Thiel
J. Phys. Chem. A, 2006, 110 (4), pp 1575–1585
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fluoroformyloxyl radical FCO2
• FCO2 radical has been postulated as an
important intermediate in the photooxidation of carbonyl difluoride, CF2O.
• FC(O)X+hn FCO*+X (X=H, F, Cl)
• FCO*+FCO* FC(O)F+CO
• FCO*+O2+M FC(O)O2+M
&
•FC(O)O2+NO FCO2+NO2
Francisco, Goldstein Chem Phys 1988)
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Experimental details (Wuppertal)
• The vacuum line (in glass) was connected to an IR gas cell optical
path length of 200 mm, Si windows 0.5 mm thick contained in the
sample compartment
• Pure samples were stored in flame-sealed glass ampoules under
liquid nitrogen in a storage Dewar vessel.
• By using an ampoule key [Gombler and H. Willner, 1987],18
ampoules were opened at the vacuum line, and after an appropriate
amount was taken out for the experiments, they were flame-sealed
again.
• FCO2 was generated by vacuum flash pyrolysis of bisfluorocarbonylperoxide FCOOOCOF. This was prepared in a flow
system according to the literature procedure [Russo et al, 1995] and
purified by trap-to-trap distillation.
• Fourier transform spectra (FTIR Bruker) recorded in Wuppertal
Complicated, …dangerous: …for
details…..ask to H. Beckers, H. Willner
from Wuppertal
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