Detection of halogen radicals by millimetre – wave spectroscopy

Detection of of halogen radicals by by
millimetre –– wave wave spectroscopy
Presented Presented by: by: Eva Grigorová Grigorov
Supervisor: Supervisor: Stephane Bailleux
Georges Wlodarczak
Zdeněk Zelinger

VŠB- Technical University of
Ostrava, faculty of Safety
engineering
eng neering
Branch of Study of Fire
Protection and Industrial
Safety
Cooperate with J.Heyrovský
J.Heyrovsk
Institute of Physical
Chemistry, Academy of
Sciences of Czech Republic
Where Where I I am am from? from?

From October 2006 in Lille 1
University in France
Laboratoire de Physique des
Lasers, Atomes et Molécules Mol cules
(PHLAM)
Study halogen radicals radicals
(CH2I) (CH I) by mmw
spectroscopy and analysis ana ysis of
ν4 band of FCO2 FCO measured
by FTIR
Present

Study theoretical
background of
spectroscopy
1. 1. Part Part of of my my work work
How to operate the
spectrometer

2. 2. Part Part of of my my work work
High igh resolution spectroscopy of halogen
Difficult to prepare
short life time - (few ms)
have to choose suitable
radicals radical
precursor
preparative process, reaction
physical conditions (pressures,
temperature)
Difficult to detect them
few weak transitions of reactive species
many strong lines of stable species

Halogen radicalss radical CH22XX CH
[ [ X X = = Cl, Cl, F, F, Br, Br, I I ] ]
1) 1) Atmospheric interest
• Reaction: Reaction:
CH 3X X + OH or Cl → CH 2X • Subsequent reactions involving CH 2X X
produce halogen atoms atom
• Destr estroying oying stratospheric ozone

2) 2) Spectroscopic interest
• CH 2F F and CH 2Cl Cl: : micro wave spectra
published more than 2 decades
ago(Y.Endo et al,1983,1984)
• CH2Br CH Br rotational otational spectrum analyzed
(Bailleux Bailleux et t al, al 2OO5)
• CH2I CH no high resolution spectroscopic
data availa available
ble
• All these radicals have planar structure

CH CH22Br
Br radical radical
Come Come
from CH3Br CH Br
natural and anthropogenic source
• In the Atmosphere:
CH 3Br Br + OH → CH 2Br Br + H O 2
• In Laboratory:
CH 3Br Br + Cl → CH 2Br Br + HCl

What What about about CH CH22I
I ??? ???
Difficultiies
Difficult es with with producing and and
detecting
No experimental data of rotational rotational
constants constant
How ow to produce ?
CH3Br CH Br + Cl → CH2Br CH Br ...exotherm
... exothermic ic reaction
CH3I CH I + Cl → CH2I CH I ...exo ... exo, , endo... endo...
Not clear
according to papers
Fine and hyperfine splitting: splitting:
II I (5/2)>IBr (5/2)>IBr(3/2)
(3/2)
Lines ines of CH 2I I are expected weaker than lines
of CH2Br CH Br:
= 0,8 < µ (CH2Br ) = 1
: µ( ( CH2I ) =
< µ(CH2Br )

CH22I CH I radical radical
CH 3I most most
abundant abun ant iodo compound in the
atmosphere
Natural atural source : pelagic ocean,
ocean surface waters, volcanic production
Previous studies studies
Only nly low resolution studies studies
Photoelectron spectra pectra
(L.Adrews L.Adrews et t al,1984 al,1984)
Matrix infrared spectrum
(D.W.Smith D.W.Smith and L.Adrews,1973
L.Adrews,1973)

How How to to detect detect CH22I? CH I?
Based on high level ab initio calculations
calculation
A = 279413,0 MHz B = 8806,1 MHz C = 8537,1 MHz
→ calculated spectrum → graph

Use Use glow glow elecctric ele tric ddiischarge scharge
...easer to use it at first
C-I I chemical bond weaker than C-Br C Br bond
Test on CH2Br CH Br radical - We produced CH2Br CH Br!

CH2I CH I in glow el. discharge ?
• many vibrationally
vibrationally
excited states of CH3I CH
Intensity
8
3
-2
-7
-12
Congested spectrum of CH3I
450000 450050 450100 450150 450200
Frequency
CH3I

Change to to hydrogen
abstraction with with fluorine
• Atomic tomic fluorine produced in microwave discharge:
Primary reaction:
CH3I CH I + F → CH2I+ CH I+ HF ???
• Test at first on CH2Br CH Br radical
CH2Br CH Br only observed using F 2 !!!

• Secondary reaction:
F + CH 2I I → [CH CH2FI FI] * → CH 2F F + I ???
• Test to detect CH 2F F → Detected !!!
CH 3I I + F → CH 3F F + I → CH 2F F + HI
• Test to detect CH 3F F → Detected!!!

• Searching for lines is still in progress... progress...
• At least observed spectra are not congested...
Intensity
8
3
-2
-7
-12
450080 450085 450090 450095 450100
Frequency
Congested spectrum of CH3I
Nocongested spectrum of
CH3I

Wish Wish
We have seen few paramagnetic lines
(probably probably from CH 2I???) I???) and therefore is
important to continuous in measurement...
measurement...

3. 3. Analysis of of νν band band of of FCO
44 FCO2 2
obtained by by FTIR FTIR
A, B, C rotational constant, centriftugal distortion constants, co stants, fine constants ???

FCO 2
Probably produced during the stratospheric
degradation of HFCs
Most stable member amongst carboxy
radicals of the type XCO 2
[X = H, F,Cl, Br, I, CF 3 , OCF 3 ]
Rotational spectrum in its ground vibrational
state in the range 240-380 GHz (Z. Zelinger
et al,2003) and 210-245 GHz (Z.Zelinger et
al, 2007)

Conclusion
Spectroscopy of radical has essential importance importance
for obtaining the information about chemistry in
the atmosphere
We will continuous in measurement...
Long Long time time prospect
After stay in France, France work with Zdeněk Zden k Zelinger
group in J.Heyrovský J.Heyrovsk Institute of Physical
Chemistry Academy of Sciences of Czech Republic
Finish inish my postgraduate study in
VŠB- Technical University of Ostrava

Thanks Thanks to to my my supervisors for for
expert expert advice advice and and patience
leading
leading

Thank Thank you you for for your your
attention