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 Length of a bunch : 10 ps Period between bunches : 10 ns Storage mode : « Top-up » 430 mA « multibunches »: 416 bunches « temporel » : 8 bunches

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) 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 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) 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

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)

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

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 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

Pure rotational transition of HN2+ in the far-Infrared Acquisition 15-40 cm-1 HN2+ 0.0025 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) 745209.868(30)a 4.1 8 9 - 8 838300(15) 838307.1(10)b -7.1 9 10 - 9 931374(15) 931386.2(10)b -12.2 10 11 - 10 1024435(15) 1024443.2(10)b -8.2 11 12 - 11 1117481(15) 1117477.1(12)b 3.9 a Amano et al., J. Mol. Spec, 234, 170 (2005) b Verhoeve et al., Rev. Sci. Instrum., 61, 1612 (1990)

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

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