1. FOURIER TRANSFORM FAR-INFRARED SPECTROSCOPY OF HN2+ ON THE AILES BEAMLINE OF SYNCHROTRON SOLEIL
O. Pirali, S. Gruet, M. Vervloet
AILES beamline, synchrotron SOLEIL
Institut des Sciences Moléculaires d’Orsay

2. Caracteristics of SOLEIL facility
Bunch of electrons accelerated in the LINAC to 100 MeV
Accelerated in the Booster to 2.75 GeV
Injected in the storage ring (113 m diameter)
Dipoles, undulators, wiggler to make the electrons « oscillating »
Loss of energy throught photon emission
Length of a bunch : 10 ps
Period between bunches : 10 ns
Storage mode :
« Top-up » 430 mA
« multibunches »: 416 bunches
« temporel » : 8 bunches

3. www.synchrotron-soleil.fr Call for beamtime every 6 months

4. FIR absorption spectroscopy of transient species
PhD Marie-Aline Martin (2012)
14NH2, 15NH2, C3,CH, NH,OH, SH, SO (TD12)
PhD Sebastien Gruet
HN2+, HCO+, H3+
DC DISCHARGE
~ 1KV / 100mA
24 m absorption
White type cell
Continuum synchrotron
RESOLUTION=30MHz
cm-1

5. Schematic view of the hollow cathode discharge cell
See e.g. S. Foster et al., J. Chem. Phys., 81,578 (1984)
10 cm
Teflon rings
Liquid N2 (output)
Evacuation
Anode
70 cm
Gas Injection
110 cm
Hollow Cathode
Windows
Beam
15 cm
Liquid N2 (input)
Pyrex Cell
Technical details
Gold mirrors
Copper electrodes
Absorption path length:
16-24 m
Max pumping speed :
250 m3.h-1
Min. cathode temperature : 77 K

6. Spectroscopy of cationic molecules+ +
H3+ : +
HN2+ :
HCO+ :
Synchrotron radiation
Michelson interferometer
New cell
Gases
Power supply
Liquid nitrogen tank
Pumping group
Detector
Experimental conditions :
Observations
(1800 – 3800 cm-1)
Molecules
H3+, HN2+ & HCO+
Resolution
H3+ (0.015 cm-1), HN2+ & HCO+ (0.007 cm-1)
Source
Internal NIR source
Detector
InSb
Beamsplitter
KBr
Windows
CaF2
Iris
H3+ (2.5 mm), HN2+ & HCO+ (1.7 mm)

7. H3+ Observation in the mid-Infrared
Temperature dependance of the H3+ abundance
See McKellar and Watson, J. Mol. Spec, 191, 215 (1998)
Wavenumber (cm-1)
Absorbance
H3+ experimental details
Acquisition time
Detector
Band observed
Resolution
Number of transitions
Cathode temperature
45 min
InSb 2
0.015 cm-1 28
77 K

8. Ro-vibrational spectra of HN2+ and HCO+ in mid-Infrared
Protonation of neutral species :
H3+ + X → HX+ + H X = N2, CO
Experimental details (HN2+ and HCO+)
Band
Acquisition time
Jmax
Number of transitions
Resolution 1
25 min
15 (HN2+), 14 (HCO+)
32 (HN2+), 29 (HCO+)
0.007 cm-1
HCO+
HN2+
Nakanaga et al., Chem.Phys. Lett., 169, 269 (1990)
Amano, J. Chem. Phys. 79, 3595 (1983).
1st FT detection of the ν1 band of HCO+ ?
Trot (HN2+ & HCO+) ≈180K

9. Pure rotational transition of HN2+ in the far-Infrared
Acquisition
15-40 cm-1
HN2+
cm-1
Synchrotron radiation
1.6 K cooled Bolometer
50 µm Mylar
Polypropylene
10 mm
Poor S/N ratio
First FT pure rotation
5 transitions recorded
Good agreement with the literature
R(J)
J’ – J’’
Our work (MHz)
Published frequencies (MHz)
Difference (MHz) 7
8 - 7
745214(15)
(30)a
4.1 8
9 - 8
838300(15)
(10)b
-7.1 9
10 - 9
931374(15)
(10)b
-12.2 10
(15)
(10)b
-8.2 11
(15)
(12)b
3.9
a Amano et al., J. Mol. Spec, 234, 170 (2005)
b Verhoeve et al., Rev. Sci. Instrum., 61, 1612 (1990)

10. Attempt using Coherent Synchrotron Radiation…
“coherent” : ITHz linear with Iring2
“ incoherent” : ITHz linear with Iring
B. Billinghurst et al., Optics letters, 35, 3090 (2012)
PhD J. Barros (2012)
Barros et al., Rev.Sci. Instrum., 84, (2013)
See talk WH15

11. Conclusion and perspectives
Ion density : 1011 molecules.cm-3
Necessity to obtain higher density of ions
≠ cathode materials, new discharge geometry
Improve the cooling system

12. Aknowledgements AILES Staff :
S. Gruet, P. Roy (BML manager), L. Manceron, J. B. Brubach, M. Chapuis,
F. Alabarse, S. Dalla Bernardina