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
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
Storage mode :
« Top-up » 430 mA
« multibunches »: 416 bunches
« temporel » : 8 bunches
Length of a bunch : 10 ps
Period between bunches : 10 ns
www.synchrotron-soleil.fr
Call for beamtime every 6 months
http://sunset.synchrotron-soleil.fr/sun
FIR absorption spectroscopy of transient species
PhD Marie-Aline Martin (2012)
14NH , 15NH , C ,CH,
2
2 3
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
20-700 cm-1
Schematic view of the hollow cathode discharge cell
See e.g. S. Foster et al., J. Chem. Phys., 81,578 (1984)
Liquid N2
(output)
Teflon
rings
Anode
Hollow
Cathode
Evacuation
15 cm
Windows
Beam
10 cm
Pyrex Cell
70 cm
Gas
Injection
Liquid N2
(input)
110 cm
Gold
mirrors
Copper
electrodes
Technical details
Absorption path length: Max pumping speed :
16-24 m
250 m3.h-1
Min. cathode
temperature : 77 K
Spectroscopy of cationic molecules
+
H3
+:
+
+
+
HN2 :
HCO+ :
Synchrotron radiation
Michelson
interferometer
Gases
Detector
New cell
Power supply
Liquid nitrogen tank
Pumping group
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)
H3+ Observation in the mid-Infrared
Temperature dependance of
the H3+ abundance
See McKellar and Watson, J. Mol. Spec, 191, 215 (1998)
0.06
77 K
144 K
185 K
214 K
271 K
0.05
Absorbance
Absorption
0.04
0.03
0.02
0.01
0.00
2725.8
2725.9
2726.0
2726.1
2726.2
-1
Wavenumber (cm )
Wavenumber (cm-1)
H3+ experimental details
Acquisition time
Detector
Band observed
Resolution
45 min
InSb
2
0.015 cm-1
Number of
transitions
28
Cathode
temperature
77 K
2726.3
Ro-vibrational spectra of HN2+ and HCO+ in mid-Infrared
Protonation of neutral species :
H3+ + X → HX+ + H2
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
R(8)
R(3)
R(2)
R(9)
R(14)
R(15)
R(10)
R(11)
R(12)
R(13)
P(1)
R(0)
P(16)
0.005
P(15)
P(14)
0.010
HN2+
R(1)
P(2)
P(11)
P(10)
P(13)
P(12)
0.015
Absorbance
P(3)
P(9)
0.020
P(7)
P(6)
P(5)
P(4)
P(8)
0.025
R(4)
R(5)
R(6)
R(7)
HCO+
0.000
-0.005
3170
3180
3190
3200
3210
3220
3230
3240
3250
3260
3270
3280
3290
-1
Wavenumber (cm )
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
Pure rotational transition of HN2+ in the far-Infrared
J = 10  9
J = 8  7
0.09
J = 12  11
0.08
Acquisition
15-40 cm-1
0.07
HN2+
0.06
24.80
24.85
24.90
24.95
31.00
31.05
31.10
31.15
J = 9  8
37.20
37.25
37.30
37.35
J = 11  10
0.0025 cm-1
Absorbance
0.05
Synchrotron radiation
0.04
1.6 K cooled Bolometer
0.03
27.90
27.95
28.00
28.05
34.10
34.15
34.20
34.25
50 µm Mylar
0.02
Polypropylene
0.01
10 mm
0.00
-0.01
-0.02
22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38
-1
Wavenumber (cm )
R(J)
7
8
9
10
11
a
b
J’ – J’’
8-7
9-8
10 - 9
11 - 10
12 - 11
Our work (MHz)
745214(15)
838300(15)
931374(15)
1024435(15)
1117481(15)
Published frequencies (MHz)
745209.868(30)a
838307.1(10)b
931386.2(10)b
1024443.2(10)b
1117477.1(12)b
Amano et al., J. Mol. Spec, 234, 170 (2005)
Verhoeve et al., Rev. Sci. Instrum., 61, 1612 (1990)
Difference (MHz)
4.1
-7.1
-12.2
-8.2
3.9
Poor S/N ratio
First FT pure rotation
5 transitions recorded
Good agreement with
the literature
9
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, 033102 (2013)
See talk WH15
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
11
Aknowledgements
AILES Staff :
S. Gruet, P. Roy (BML manager), L. Manceron, J. B. Brubach, M. Chapuis,
F. Alabarse, S. Dalla Bernardina