High-J rotational lines of HCO + and its isotopologues measured by using Evenson-type tunable FIR spectrometer R. Oishi, T. Miyamoto, M. Suzuki, Y. Moriwaki, F. Matsushima Department of Physics, University of Toyama, Japan T. Amano Department of Chemistry, University of Waterloo, Canada

Background /Spectroscopy of HCO + Rotational transitions 1970 Buhl and Snyder: Discovery of “X-ogen” 1975 Woods et al: Laboratory identification of “X-ogen” HCO Buffa et al 2007 Tinti et al 2012 Cazzoli et al Extension to higher-J lines, up to J= Vibration-rotation transitions (IR) 1983 Gudeman et al: ν 1 band ( R(0) to R(18) ) Amano: ν 1 band (P(10) to R(9) ) Verbraak et al: CRD with with cw-OPO 2013 Siller et al: Lamb dip with cw-OPO and frequency comb → “Indirect” measurements of the rotational transitions up to J ≤ 10 In this investigation: Extended precise measurements of the rotational lines to higher-J

TuFIR spectrometer at University of Toyama FIR =| I - II |± MW

Extended negative glow discharge cell Pressure H 2 : 0.3Pa, CO: 0.3Pa, Ar: 2.4Pa Discharge current: 10 〜 20mA, voltage 1 〜 3.5kV Cell: Diameter: 32mm, length 1.5m

汚れた内管の写真 Replaceable double jacketed discharge tube with liquid nitrogen cooling capability Two straight glass tubing with different diameters are assembled with plastic flange and heat-shrink tubing → easy replacement of soiled inner tubing

(36) MHz (63) MHz Measurement of HCO + rotational lines J=11<-10 J=22<-21

Measured Transition Frequencies for HCO + J’ J obs/MHz (o-c)/kHz J’ J obs/MHz (o-c)/kHz Cazzoli et al, ApJS, 203, 11 ( 2012) Sastry et al, JCP, 75, 4169 (1981)

B /MHz ( 157) (27) D /kHz ( 22) (60) H /Hz ( 108) 0.137(46) L /mHz ( 145) (91) H = BJ(J+1) –D[J(J+1)] 2 + H[J(J+1)] 3 +L[J(J+1)] 4 Molecular constants for HCO + Present Cazzoli et al a a G. Cazzoli, L. Cludi, G. Buffa, C. Puzzarini, ApJS. 203, 11 (2012)

(36) MHz (58) MHz Measurement of DCO + rotational lines J=14<-13 J=25<-24

Measured Transition Frequencies for DCO + J’ F’ J F obs/MHz (o-c)/kHz J’ J obs/MHz (o-c)/kHz Caselli and Dore, A&A, 433, 1145 (2005) Lattanzi et al, ApJ, 662, 771 (2007)

B /MHz (34) (14) D /kHz (34) (22) H /Hz.0920( 96) 0.054(11) L /mHz (82) c /kHz -1.34(233) -1.59(78) eQq /kHz 148.0(101) 147.8(35) Molecular Constants for DCO+ Present Caselli and Dore a a P. Caselli and L. Dore, A&A, 433, 1145 (2005)

ln I/(J+1) E low /MHz Rotational Temperature ≈ 120K Rotational Temperature To reach higher-J lines: Higher cell temperature Decrease the density of ions

N 2 H + J=5←4 temperature dependence, sub-mm spectrometer -200C (liq. N2 temp) (room temp.)

Summary  HCO +,DCO + : Frequencies of rotational lines with high J-quantum numbers were measured precisely using a TuFIR spectrometer.  Rotational parameters were improved.  Measutements of 13 C isotopologues: H 13 CO + and D 13 CO + are in progress.

Acknowledgment  Grant-in-Aid from the Ministry of Education, Culture, Sports, Science and Technology of Japan  Natural Science and Engineering Research Council of Canada (NSERC)  Department of Chemistry, University of Waterloo

TuFIR (CO 2 laser difference frequency) How to obtain the tunability using wave guide CO 2 laserusing MW source tunability ~ 100MHz need many combinations tunability ~ 20GHz power: 2 nd > 3 rd

Simulation of the absorption intensity I=abs.int. μ=dipole moment B=rotational constant (cm -1 ) h=Plank constant k=Boltzman constant (cm -1 /deg) J 77K 120K 300K Abs.int (arb.units)