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. AmanoDepartment 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+ . 2006 Buffa et al 2007 Tinti et al 2012 Cazzoli et al Extension to higher-J lines , up to J=17 - 16. Vibration-rotation transitions (IR) 1983 　 Gudeman et al: ν1 band ( R(0) to R(18) )

Amano: ν1 band (P(10) to R(9) )

. 2007 　 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 ≤ 10In 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 H2: 0.3Pa, CO: 0.3Pa, Ar: 2.4PaDischarge 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

980636.508 (36) MHz

1958629.025 (63) MHz

Measurement of HCO+ rotational lines

J=11<-10

J=22<-21

1 0 89188.5247 -1.5 2 1 178375.0563 -8.1 3 2 267557.619 -8 4 3 356734.2230 -1.7 5 4 445902.8721 0.8 6 5 535061.5810 2.1 7 6 624208.3606 -0.1 8 7 713341.2278 -1.9 9 8 802458.1995 -0.5 10 9 891557.2903 4.7

11 10 980636.510 9 12 11 1069693.850 -12 13 12 1158727.429 45 14 13 1247735.112 29 15 14 1336714.999 23 16 15 1425665.082 3 17 16 1514583.352 -57 18 17 1603468.010 25 19 18 1692316.839 16 20 19 1781127.946 6 22 21 1958629.075 -7

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 44594.428788( 157) 44594.42895(27) D /kHz 82.8370( 22) 82.8412(60) H /Hz 0.1011( 108) 0.137(46) L /mHz -0.0359( 145) -0.118(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 ala

a G. Cazzoli, L. Cludi, G. Buffa, C. Puzzarini, ApJS. 203, 11 (2012)

1007941.236 (36) MHz

1797504.091 (58) MHz

Measurement of DCO+ rotational lines

J=14<-13

J=25<-24

1 0 0 1 72039.2413 -0.3 1 2 0 1 72039.3028 -1.3 1 1 0 1 72039.3504 -0.8 2 1 144077.2890 2.5 3 2 216112.5822 0.5 4 3 288143.8583 -1.1 5 4 360169.7783 -2.4 6 5 432189.0052 -1.8 7 6 504200.1999 -0.1 8 7 576202.0239 2.2 9 8 648193.1357 1.3 10 9 720172.2024 1.7 11 10 792137.8811 -2.8

12 11 864088.890 47 13 12 936023.7532 -1.4 14 13 1007941.254 -16 15 14 1079840.081 24 16 15 1151718.735 -45 17 16 1223576.080 -24 18 17 1295410.668 -24 19 18 1367221.232 25 20 19 1439006.283 -30 21 20 1510764.676 5 22 21 1582494.967 24 23 22 1654195.707 -79 24 23 1725866.004 147 25 24 1797503.697 -118

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 36019.76805(34) 36019.76765(14) D /kHz 55.8029(34) 55.7960(22) H /Hz .0920( 96) 0.054(11) L /mHz -.0469(82)

c /kHz -1.34(233) -1.59(78)eQq /kHz 148.0(101) 147.8(35)

Molecular Constants for DCO+

Present Caselli and Dorea

a P. Caselli and L. Dore, A&A, 433, 1145 (2005)

0 10000000 20000000 30000000

-4

-3

-2

-1

0

1

2

3

4

ln I/

(J+

1)

Elow /MHz

Rotational Temperature ≈ 120K

Rotational Temperature

To reach higher-J lines:• Higher cell temperature• Decrease the density of ions

N2H+ J=5←4 temperature dependence, sub-mm spectrometer

-200C (liq. N2 temp)-100 -85 -65 -30 -15 -5 +20 (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 13C isotopologues: H13CO+

and D13CO+ 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 (CO2 laser difference frequency)How to obtain the tunability

using wave guide CO2 laser using MW source

tunability ~ 100MHzneed many combinations

tunability ~ 20GHz

power: 2nd > 3rd

Simulation of the absorption intensity

I 2 fJ(2J 1)

fJ (2J 1)e

hBJ(J1)kT

(2J 1)e hBn(n1)

kT

n0

50

I=abs.int.μ=dipole momentB=rotational constant 1.201492049(cm-1)h=Plank constantk=Boltzman constant 0.69501(cm-1/deg) J

77K120K

300K

Abs

.int

(arb

.uni

ts)