coherent synchrotron radiation for rotational spectroscopy : application to propynal in the 200-750...
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Coherent Synchrotron Radiation for Rotational Spectroscopy : application to
Propynal in the 200-750 GHz rangeJ.Barros P.Roy L.Manceron
SOLEIL - AILES beamline - France D.Apadoo, D. McNaughton E. Robertson
Australian Light source and Monash U.
MSS Columbus 2013
Outline
Introduction1. CSR generation2. Adaptation to AILES beamline3. Noise correction4. Use of CSR for measurements on Propynal
High Resolution IR spectroscopy with Synchrotron Radiation
Introduction
Synchrotron beam
Bruker 125HR Interferometer
resolution: 0.001 cm-1
Bolometer
path difference
14x103
12
10
8
6
4
2
0
Inte
nsité
(u.a
.)
wavenumber
Fourier
Transform
MOPD
8.82 m
Fixed mirror
Moving mirror
1MSS Columbus 2013
10
Emission modes
depends on sz (electron bunch length) and on the current
1. CSR generation
N≈108 l < sz incoherent emissionEmission mode
4MSS Columbus 2013
N≈108
10
l < sz incoherent emission
Emission mode
Emission modes
l ≥ sz coherent emission
CSR
depends on sz (electron bunch length) and on the current
1. CSR generation
4
“Clearly the promise of a bright, high-power THz continuum source is attractive. However, we note that CSR is itself a non-linear effect and so may
tend to be inherently noisy.”
R. W. McKellar, J. Mol. Spectrosc. 262, 1 (2010)«High Resolution IR spectroscopy with synchrotron radiation»
CSR instabilities
Microbunching: interaction of an electron bunch with its own emitted radiation
Bunch profile modulation
C. Evain, J. Barros et al., EPL 98, 40006 (2012)
1. CSR generation
5MSS Columbus 2013
CSR instabilities
Microbunching: interaction of an electron bunch with its own emitted radiation
Bunch profile modulation
C. Evain, J. Barros et al., EPL 98, 40006 (2012)
1. CSR generation
5MSS Columbus 2013
CSR instabilities
Microbunching: interaction of an electron bunch with its own emitted radiation
Bunch profile modulation
C. Evain, J. Barros et al., EPL 98, 40006 (2012)
1. CSR generation
Fluxscales with NN≈108 l < sz incoherent emission
Emission mode
l ≥ sz coherent emission scales with N²
Microstructures emit coherently
very irregular
5MSS Columbus 2013
Effect of increasing current
No detected CSR
2. Adaptation to the AILES beamline
6MSS Columbus 2013
Effect of increasing current
No detected CSR
CSR appearsGain in
intensity: 104 to 105
2. Adaptation to the AILES beamline
6MSS Columbus 2013
Effect of increasing current
No detected CSR
CSR appearsGain in
intensity: 104 to 105
Microbunching instability
2. Adaptation to the AILES beamline
6MSS Columbus 2013
Effect of bunch length
Stability zone in bunch length and current
2. Adaptation to the AILES beamline
7MSS Columbus 2013
Broadband source, but still some remaining noise at given frequenciesEffect of microbunching evidenced even under threshold2
2. Adaptation to the AILES beamline
Signal spectral distribution Noise frequencies
9MSS Columbus 2013
Noise correction setup
Synchrotron beam
Bruker 125HR Interferometer
Bolometer 1Interferogram
+ perturbation
3. Noise correction
11MSS Columbus 2013
Noise correction setup
3. Noise correction
Synchrotron beam
Bruker 125HR Interferometer
Bolometer 1Interferogram
+ perturbation
6 µm Mylar beamsplitter
R/T≈0,2
Bolometer 2Perturbation
only
11MSS Columbus 2013
Noise correction setup
3. Noise correction
4.2 K composite bolometers with identical 0-200 cm-1 filters, same solid angle, same preamplifiersSimultaneous acquisition
Synchrotron beam
Bruker 125HR Interferometer
Bolometer 1Interferogram
+ perturbation
6 µm Mylar beamsplitter
R/T≈0,2
Bolometer 2Perturbation
only
Post-treatment: subtraction of the 2 temporal signals FT
11MSS Columbus 2013
Correction examples
Periodic perturbationArtifact on an absorbance spectrum compensated
White noise correction
Aperiodic, bursting perturbationTop-up correction: effect on spectrum
3. Noise correction
12MSS Columbus 2013
Correction examples
3. Noise correction
Example on a 45 min spectrumRes = 0.001 cm-1
Pure rotational line of N2O with an intensity of9.0∙10-23 cm-1/(moleculexcm²) Gain of 5 in S/N
J. Barros and coll. Rev. Sci. Inst. 84, 033102(2013)
13MSS Columbus 2013
Application
Rotational spectrum of propynal0.225 mbar in 885 cm, 9h, bolometer 4.2 K
About 1200 pure rotational transitions in the ground statePrevious works: Winnewisser, 1972 (90 transitions)McKellar (IR combination differences)
Fit of the ground state (Watson a-type Hamiltonian)
4. Propynal
15MSS Columbus 2013
Application
Rotational spectrum of propynal0.225 mbar in 885 cm, 9h, bolometer 4.2 K
4. Propynal
14
Application
J=38 → 39 J=39 → 40
not present in the fit
Spectrum
Simulation
4. Propynal
16MSS Columbus 2013
Some improvements in the molecular constants
MSS Columbus 2013
Constants this work (MHz) Winnewisser (MHz) McKellar et al. (MHz)
RotationalABC
a68035,308 (025)
b4826,28805 (097)4499,52695 (095)
68035,299 (043)4826,3014 (073)4499,5107 (069)
68035,263 (039)4826,293 (006)4497,15 (006)
Centrifugal Distorsion QuarticΔJ
ΔJK
ΔK
δJ
δK
a1,91792 (111) · 10-3
a-0,1481185 (186)a9,0033 (057)
a3,37419 (151) · 10-4
b0,03396 (026)
1,917 (012) · 10-3
-0,148102 (047)8,991240 (9730)3,458 (014) · 10-4
0,019500 (1590)
1,913 (004) · 10-3
-0,148044 (039)8,993 (009)
3,454 (012) · 10-4
0,0347 (028)
SexticHJK
HKJ
HK
HJ
-0,8348 (082) · 10-6
b-8,245 (107) · 10-6
3,190 (147) · 10-3
7,549 (214) · 10-9
-7,41 (059) · 10-7
-8,310 (130) · 10-6
----
-7,11 (048) · 10-7
-8,24 (012) · 10-6
2,36 (006) · 10-3
--
Conclusions
Extension of SR spectral range at SOLEIL
BUT Limited Resolution (30MHz..)
- Time-saving for studies of unstable molecules- Combination with IR studies on the same setups- Intensity studies are possible
Frequency
0.1 THz 1 THz 10 THz 100 THz
ISRHigh res.
Wavenumber
3.3 cm-1 33 cm-1 330 cm-1 3300 cm-1
CSRHigh res.
17MSS Columbus 2013
Two important WEB Pages :
http://www.synchrotron-soleil.fr/
For general informations
http://www.synchrotron-soleil.fr/portal/page/portal/Recherche/LignesLumiere/AILES
and, for proposal submissions :
http://sunset.synchrotron-soleil.fr/sun/
twice a year : mid-september and –february deadlines. Proposals (submissions in English) ranked by an international peer-review committee.
How to submit your proposals
Support from User Office
Preparing your experiment
Safety requirements
Beamline AILES: Mid IR to THz Spectroscopy
Acknowledgements
Lille:Clément EvainSerge BielawskiChristophe Szwaj
SOLEIL- Machine:Marie-Emmanuelle CouprieMarie-Agnès TordeuxPascale BrunelleLaurent NadolskiAlex LoulergueMarie LabatLodovico CassinariRyutaro NagaokaAmor Nadji
MSS Columbus 2013
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