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Generation of THz radiation June 25, 2015ISMS, 2015  Direct generation ; Backward-wave oscillator (BWO) < ~1.2 THz  Sideband generation of FIR lasers and microwave Saykally, Nijmegen group  Difference frequency between two IR lasers, typically CO 2 lasers in 9 – 11 μm, and microwave with MIM diode “TuFIR” University of Toyama  Up-conversion from low-frequency sources Commercial multiplier ( Millitech, Verginia Diode) Custom-made

Sub-millimeter to THz Spectrometer June 25, 2015ISMS, 2015 THz radiation sources Multiplier chain BWO Ion generation Extended negative glow B. J. Drouin et at, RSI. 76, (2005) J. C. Pearson et al, RSI. 82, (2011)

Examples of observed signals June 25, 2015ISMS, 2015 The extended negative glow discharge in a gas mixture of H 2 ~ 2mTorr, D 2 ~2 mTorr, and Ar ~17 mTorr, and the cell was cooled to liquid nitrogen temperature.

D 2 H + as an interstellar molecule 1984 First infrared detection. ν 1 fundamental band Lubic and Amano, Can. J. Phys. 62, 1886 (1984) Foster, McKellar, and Watson (1986), ν 2 and ν 3 Pure rotational transitions observed by high-resolution spectroscopy have been limited so far to the J KaKc = transition at GHz and J KaKc =2 20 – 2 11 at THz, and J KaKc =1 11 – 0 00 at THz. Evenson et al, unpublished. Hirao and Amano, Astrophys. J. 597, L85 (2003) Asvany et al, Phys. Rev. Lett. 100, (2008) June 25, 2015ISMS, 2015 Vastel, Phillips, and Yoshida, Astrophys. J. 606, L127 (2004) Astronomical identification, 16293E B. Parise et al, A&A. 526, A31 (2012) Further confirmation of the detection This ion plays a pivotal role in the deuterium fractionations in cold pre-stellar cores.

Laboratory Observations June 25, 2015ISMS, 2015 As this ion is a light asymmetric-top molecule, spectroscopic characterization and prediction of other rotational transition frequencies are not straightforward. Pure rotational lines alone are not enough to fully characterize the spectroscopic property of this light molecule.  D 2 H + was generated in an extended negative glow discharge in a gas mixture of H 2 ~ 2mTorr, D 2 ~ 2 mTorr, and Ar ~17 mTorr.  The cell was cooled to liquid nitrogen temperature.  Although the line density was very sparse, careful chemical checks were carried out to ascertain that the lines observed were indeed the ones from D 2 H +.  Four new THz lines up to 2 THz were observed and re-measured the two out of the three known transitions. cm KaKa ortho- para- 3 22

Spectroscopic Analysis June 25, 2015ISMS, 2015 Observed data were fit to the Watson A-reduced Hamiltonian. However, to fit the data to the observed accuracy ( ~ 100 kHz), seven pure rotational line frequencies were not sufficient. Therefore, as done in the previous analysis, combination differences derived from the three fundamental bands were fitted together with the rotational lines.

Results June 25, 2015ISMS, – (20) a – (100) – (100) – (3) b – (15) c – (100) – (100) 5 The least squares fit was made with seven sub-mm and THz lines together with 42 combination differences derived from the IR fundamental bands. a Amano and Hirao, J. Mol. Spectrosc., 233, 7 (2005) b Evenson et al, unpublished. c Asvany et al, Phys. Rev. Lett., 100, (2008) A (20) B (46) C (26) Δ J (30) Δ JK 88.5(34) Δ K (140) δ J (79) δ K (150) Φ JK 1.350(166) Φ KJ -3.56(47) Φ K 4.50(56) Molecular constants ( in MHz ) Observed transition frequencies Frequency/MHz (o-c)/kHz

Discussion June 25, 2015ISMS, 2015 A (20) (23) (114) B (46) (138) (123) C (26) (57) (99) Δ J (30) (51) (47) Δ JK 88.5(34) 70.8(20) 69.3(27) Δ K (140) (177) 592.9(40) δ J (79) (192) 63.36(21) δ K (150) 357.3(30) 353.5(28) Φ JK 1.350(166) Φ KJ -3.56(47) Φ K 4.50(56) Comparison of the molecular constants ( in MHz ) Present Amano, Hirao a Polyansky, McKellar b a J. Mol. Spectrosc. 233, 7 (2005) b J. Chem. Phys. 92, 4039 (1990)

Prediction of the line frequencies June 25, 2015ISMS, 2015 Ortho – (15) – (26) – (23) 7.31 Para – (48) – (95) – (43) 8.32 Frequency/MHz α / cm -1 α; Absorption coefficient calculated by assuming μ b =0.5 D and T=200 K. The spin weight is not incorporated. 4 cm KaKa ortho- para

 A part of this research was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.  A part of this research was supported by Natural Science and Engineering Research Council of Canada ( NSERC ) June 25, 2015ISMS, 2015

June 25, 2015ISMS, 2015