Beamline AILES : Mid IR to THz Spectroscopy

The AILES Infrared and THz High Resolution Spectroscopy beamline at SOLEIL (Saclay, 30 km south of Paris) – LISA CNRS-

Université Paris Est

A new Low temperature long path gas cell for Mid IR to THz spectroscopy with

Synchrotron Radiation

Soleil: L. Lago, M. Chapuis, F. Willaert, L. Manceron, P. RoyLISA: F. Kwabia Tchana, X. Landsheere, JM Flaud

Beamline AILES : Mid IR to THz Spectroscopy

AILES = Beamline on Synchrotron SOLEIL and Experimental Station with High Resolution Interferometer (0.001 cm-1 max.)

Open User facility for the Molecular Spectroscopy Community

for Broad Band Absorption Spectroscopy in the mid to Far Infrared Specifications for a long path cell :

- Variable optical path : 3 to ~150m. Spectral range 4000 to 10 cm-1

-Temperature adjustable in the 100 to 400K range, homogeneity and control within ±1K.- Pressure 1000 to 0.1 mb, measured with ±2%.- Resistance to mildly corrosive compounds.- Optical Transmission ≥ 10%. Diamond windows → HR mirrors.- Mechanical stability (vibration free pumping) optical stability.- Rapid adjustment of optical path length.

Beamline AILES : Mid IR to THz Spectroscopy

Optics:Classical White Configuration

Limitations for FIR-THz…

Instead : Chernin Configuration

Beamline AILES : Mid IR to THz Spectroscopy

In short: UHV design , base pressure 5.10-8 mbar after bake-out, Ionic Pumping : vibration-free

Objectives : Accurate far infrared high resolution spectra of diluted gas samples and mixture at temperatures : 400 - 100K

Adapted optics for long path (<150m in Far IR, )

Four compartments chamber :• Sample gas • Convection-cooling gas (He)• Liquid Nitrogen reservoir• Insulating vacuum

1m

Beamline AILES : Mid IR to THz Spectroscopy

Beamline AILES : Mid IR to THz Spectroscopy

Optics, temperature sensors,heaters

In operation coupled to the IFS 125…

Diamond windows, viewports

Beamline AILES : Mid IR to THz Spectroscopy

0 20 40 60 80 100 120 140 160 180

-250

-200

-150

-100

-50

0

(5)(4)(3)(2)

Te

mp

era

ture

(°C

)

Position along cell axis (cm)

20.4 (0.2) 0.9 (0.8) - 31.0(0.5) - 48.7 (1.2) - 64.2 (1.2) -103.0 (0.6) -146 (2.5) -167 (1.5) - 189 (5)

Folded optical path domain

(1)

Temperature… adjustable, regulated from 400 to 80K

Beamline AILES : Mid IR to THz Spectroscopy

Optical path from 3 to 141m

Linearity of detection

Beamline AILES : Mid IR to THz Spectroscopy

For intensity measurements of low Vapor Pressure Volatile Organic Compounds:Need for precise Pressure in the 0.01-100 mbar rangeNo cryogenic gauge commercially available!

Home made precision Capacitive gauge for operation down to 77K

Principle : measurement of thin metal membrane deflection by a capacitive sensor designed for low temperature

0 10 20 30 40 500

10

20

30

40

Def

lexi

on a

t ce

nter

(in

µm

)

Pressure (mb)

100 µm Inconel membrane

electrodes

GAS

Vacuum

0,01 0,1 1 10

0,1

1

10

Pré

cisi

on r

elat

ive

(%)

Pression (mbar)

…and Pressure

Beamline AILES : Mid IR to THz Spectroscopy

Some examples :

Transmission

(a)

(b)

Transmission

Transmission

(a)

(b)

C3H8 :HR measurements in the 7 to 30 µmAt low temperature for line by line analysis

SF6 : Observation of the υ6

IR and R -forbidden band

See talk RI08 V. Boudon….

Beamline AILES : Mid IR to THz Spectroscopy

Or lower in the far IR…

CH4 Distorsion- induced rotational spectrum at Low T

SF6 : Observation of weak difference bands (here υ3- υ1)

Beamline AILES : Mid IR to THz Spectroscopy

SOLEIL: Open User Facility , contact beamline scientists if interested…

Two important WEB Pages :• http://www.synchrotron-soleil.fr/

For general informations, how to contact us…

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