1. Frequency Measurement of the Terahertz Rotational Lines of H 13 CO + and D 13 CO + Mari Suzuki a, Ryo Oishi a, Fusakazu Matsushima a, Yoshiki Moriwaki a,Takayoshi Amano b （ Univ. of Toyama a, Univ. of Waterloo b ) 1

2. History HCO + : important ion as interstellar molecule Searches in interstellar space (Hershel, ALMA, SOFIA) protoplanetary nebulae, Star forming region, Hale-Bopp Comet Ubiquitous in space: abundance (and its isotopic ratio), location --> good probe of physical/chemical circumstance of interstellar space Basic molecular ion containing carbon --> study of the origin of life Laboratory rotational spectroscopy First found in space in 1970 --> trigger of laboratory work But limitted to rather low-J states (<~ J=10 ) Extend the J-range with TuFIR Obtain precise frequencies for higer J lines and improve molecular constants. 2

3. HCO + and laboratory spectroscopy Rotational transitions 1970 Buhl and Snyder; Discovery of “X-ogen” 1975 R. C. Woods et al.; Loboratory 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.; ν 1 band R(0) to R(18) Amano ν 1 band P(10) to R(9) 2007 Verbraak et al.; ν 1 band R(0) to R(5) measured using CRD and cw-OPO 2013 Siller et al.; Lamb-dip with cw-OPO and frequency comb →”Indirect” measurements of rotational transitions up to J=10 Our work H 13 CO + ; J=12←11 to J=22←21 D 13 CO + ; J=14←13 to J=26←25 Improve molecular constants 3

4. TuFIR spectrometer ν FIR =|ν Ⅰ -ν Ⅱ |±ν MW Specifications ・ range: 0.3THz 〜 6THz ・ precision: about 30kHz ・ simplified structure of the double-layer discharge cell 4

5. CO 2 fluorescence cell Laser frequency (cavity length) 4.3  m fluorescence 1st derivative Stabilization of the CO 2 laser frequency Accuracy of laser stabilization one CO 2 laser 25kHz → difference frequency 〜 36kHz 5

6. Extended negative glow discharge cell ・ Discharge current:10 〜 20 mA ・ Voltage 1 〜 3.5 kV 6

7. 2.4Pa 0.3 Pa About 0.6 sccm Gas handling system *sccm=0.01cm 3 /s 7

8. Measurement of H 13 CO + rotational lines H 13 CO + J=12←11 1040513.275 (35)MHz H 13 CO + J=21←20 1818942.810(102)MHz 8

9. Measurement of D 13 CO + rotational lines D 13 CO + J=21←20 1483424.465(40) MHz 1694650.951 (46)MHz D 13 CO + J=24←23 9

10. Measurement of H 13 CO + transitionAverage FrequencyKöln o-c * J=12<-111040513.286(36)1040513.297-0.01 J=14<-131213703.981(36)1213703.904 0.08 J=15<-141300260.681(36)1300260.652 0.03 J=16<-151386789.311(36)1386789.192 0.12 J=17<-161473287.686(36)1473287.648 0.04 J=18<-171559754.086(36)1559754.143-0.06 J=20<-191732583.721(47)1732583.750-0.03 J=21<-201818942.928(96)1818943.113-0.19 J=22<-211905263.006(56)1905263.019-0.01 *o-c=(present measurement)-(Köln prediction) [MHz] 10

11. Measurement of D 13 CO + transitionAverage FrequencyKölno-c * J=14<-13989681.850(36)989681.7790.072 J=15<-141060280.540(36)1060280.4390.102 J=16<-151130859.973(36)1130859.8530.120 J=17<-161201418.986(36)1201418.8340.152 J=18<-171271956.318(36)1271956.0110.308 J=19<-181342470.381(36)1342470.1350.246 J=21<-201483424.419(36)1483424.1140.305 J=22<-211553861.944(36)1553861.4130.531 J=23<-221624271.171(36)1624270.5470.624 J=25<-241765000.034(38)1764999.2190.815 J=26<-251835317.167(50)1835316.2030.963 *o-c=(present measurement)-(Köln prediction) [MHz] 11

12. Rotational constants of H 13 CO + rotational energy E=BJ(J+1) ー D 〔 J(J+1) 〕 ２ +H 〔 J(J+1) 〕 3 +L 〔 J(J+1) 〕 4 … 12 Köln 〔 MHz 〕 present 〔 MHz 〕 B43377.30106(51)43377.3031(20) D7.8386(27)×10 -2 7.84218(83) ×10 -2 H6.1(11)×10 -8

13. Rotational constants of D 13 CO + rotational energy E=BJ(J+1) ー D 〔 J(J+1) 〕 ２ +H 〔 J(J+1) 〕 3 +L 〔 J(J+1) 〕 4 … 13 Köln 〔 MHz 〕 present 〔 MHz 〕 B 35366.71005(24) 35366.70934(40) D 5.34189(65)x10 -2 5.34050(38)x10 -2 H 1.57(65)x10 -7 0.498(97)x10 -7 L -3.6(20)x10 -10 -0.108(74)x10 -10

14. Measured lines TuFIR D 13 CO + H 13 CO + H 13 CO + : J=12←11 to 22←21 D 13 CO + : J=14←13 to 26←25 Can we measure still higher-J lines?? No! We could not. 14

15. Analysis D 13 CO + H 13 CO + →92.6(21) K→115.7(16) K Intensity of spectral line 15

16. N 2 H + J=5←4 temperature dependence, sub-mm spectrometer (by Amano san) 16 77K (liq. N2 temp) 170K 185K 210K 240K 260K 270K 300K(room temp.)

17. Simulation of the absorption intensity I=abs. int. μ=dipole moment B=rotational constant 1.554(cm -1 ) h=Planck constant k=Boltzmann constant 0.69501(cm -1 /deg) 194K 300K ０ 10 20 30 100K Abs.int (arb.units) 17

18. Summary ・ Frequency of rotational lines with high J-quantum numbers were measured precisely using TuFIR spectrometer. →H 13 CO + : 9 lines →D 13 CO + : 11 lines ・ Rotational parameters were improved. Now preparing Measurement of 18 O isotopologues : H 12 C 18 O +, D 12 C 18 O + 18

19. Thank you! 19

20. J Obs 〔 MHz 〕 Cal 〔 MHz 〕 O-C 〔 MHz 〕 12<-111040513.292(35)1040513.315-0.023 12<-111040513.275(35)1040513.315-0.040 12<-111040513.290(35)1040513.315-0.025 15<-141300260.687(36)1300260.677 0.010 15<-141300260.676(36)1300260.677-0.001 15<-141300260.680(36)1300260.677 0.003 16<-151386789.286(39)1386789.220 0.066 16<-151386789.326(37)1386789.220 0.106 16<-151386789.318(37)1386789.220 0.098 17<-161473287.589(47)1473287.679-0.090 17<-161473287.635(36)1473287.679-0.044 17<-161473287.620(36)1473287.679-0.059 17<-161473287.594(36)1473287.679-0.085 18<-171559754.092(44)1559754.179-0.087 18<-171559754.074(44)1559754.179-0.105 18<-171559754.092(42)1559754.179-0.087 14<-131213703.968(36)1213703.926 0.042 14<-131213703.991(36)1213703.926 0.065 14<-131213703.985(36)1213703.926 0.059 19<-181646186.869(38)1646186.842 0.027 19<-181646186.887(39)1646186.842 0.045 19<-181646186.829(38)1646186.842-0.013 19<-191732583.816(46)1732583.795 0.021 20<-191732583.808(45)1732583.795 0.013 20<-191732583.868(41)1732583.795 0.073 H 13 CO +

21. 21 H 13 CO +

22. D 13 CO + J Obs 〔 MHz 〕 Cal 〔 MHz 〕 O-C 〔 MHz 〕 14<-13989681.848(38)989681.840 0.008 14<-13989681.848(38)989681.840 0.008 14<-13989681.855(39)989681.840 0.015 15<-141060280.569(55)1060280.525 0.044 15<-141060280.534(36)1060280.525 0.009 15<-141060280.497(40)1060280.525-0.028 15<-141060280.539(36)1060280.525 0.014 15<-141060280.563(36)1060280.525 0.038 15<-141060280.548(36)1060280.525 0.023 16<-151130859.976(36)1130860.002-0.026 16<-151130859.976(37)1130860.002-0.026 16<-151130859.967(37)1130860.002-0.035 17<-161201418.988(37)1201418.992-0.004 17<-161201418.990(37)1201418.992-0.002 17<-161201418.980(36)1201418.992-0.012 18<-171271956.323(36)1271956.217 0.106 18<-171271956.323(36)1271956.217 0.106 18<-171271956.309(36)1271956.217 0.092 19<-181342470.368(37)1342470.399-0.031 19<-181342470.377(37)1342470.399-0.022

23. D 13 CO + J Obs 〔 MHz 〕 Cal 〔 MHz 〕 O-C 〔 MHz 〕 19<-181342470.397(37)1342470.399-0.002 21<-201483424.465(40)1483424.522-0.057 21<-201483424.396(40)1483424.522-0.126 21<-201483424.394(41)1483424.522-0.128 22<-211553861.960(57)1553861.909 0.051 22<-211553861.958(75)1553861.909 0.049 22<-211553861.991(65)1553861.909 0.082 22<-211553861.943(48)1553861.909 0.034 22<-211553861.898(50)1553861.909-0.011 23<-221624271.117(54)1624271.144-0.027 23<-221624271.145(45)1624271.144 0.001 23<-221624271.257(52)1624271.144 0.113 25<-241765000.210(105)1765000.043 0.167 25<-241765000.122(160)1765000.043 0.079 25<-241765000.081(142)1765000.043 0.038 25<-241764999.989(63)1765000.043-0.054 25<-241764999.993(62)1765000.043-0.050 26<-251835316.888(110)1835317.154-0.266 26<-251835317.260(77)1835317.154 0.106 26<-251835317.213(80)1835317.154 0.059

24. 24 D 13 CO +

25. Rotational constant of H 13 CO + rotational energy E=BJ(J+1) ー D 〔 J(J+1) 〕 ２ +H 〔 J(J+1) 〕 3 +L 〔 J(J+1) 〕 4 … 25 Köln 〔 MHz 〕 present 〔 MHz 〕 B 43377.30106(51) 43377.2988(30) D 7.8386(27)x10 -2 7.8380(15)x10 -2 H -6.2(43)x10 -8 L 1.02(42)x10 -10