1. Mitsunori ARAKI, Hiromichi WAKO, Kei NIWAYAMA and Koichi TSUKIYAMA○
Electronic Transition Spectra of Thiophenoxy and Phenoxy Radicals in Hollow cathode discharges
Tokyo Univ. Science
Mitsunori ARAKI, Hiromichi WAKO,
Kei NIWAYAMA and Koichi TSUKIYAMA○
2018/11/11
2014/06/16

2. Diffuse Interstellar Bands
Electronic
Transition
A or B
Absorption ★ X
Diffuse
Cloud
Optical absorption lines by molecule in diffuse cloud
Near infrared ~ optical (line width: Å)
First report: 1922
~600 lines
2018/11/11

3. What are origins of DIBs ?
Optical Transition 　
Ion and/or radical
Large Molecule
Not Identified yet
Identification of DIBs
by Laboratory Spectroscopy
2018/11/11

4. Unidentified molecule
How to identify DIBs ?
Optical Electronic Transition
Space
Earth
absorption
Star
Unidentified molecule
DIB
Lab
Molecule
Spectrometer
Discharge etc
Spectra
Identification
fit
2018/11/11

5. Cavity Ring Down Spectrometer
Pulsed dye laser, 10 Hz, Dn = 0.1 cm-1
Hollow Cathode Discharge
Discharge cell - G
Electrodes
2018/11/11

6. Thiophenoxy Radical C6H5S
Rotational Profile
Model molecule to discuss
Non-Boltzmann Distribution
in diffuse cloud
Radical: Optical Transition
10% of interstellar molecules -> Sulfide
Simple PAH
Good candidate of DIB
Dose it fit to DIBs?
2018/11/11

7. Reported Laboratory Spectrum
Electronic Transition
2A2 ‹- X2B1
DIBs
Disturbed
LIF
Origin ×
Shibuya et al., Chemical Physics, 121, , 1988
2018/11/11

8. HD204827 having DIBs HD204827 The ８th Magnitude Star Galactic Plane
Celestial North Pole
Galactic Plane
HD204827
The ８th Magnitude Star
2018/11/11

9. DIBs and Reported Laboratory Spectrum
HD204827
DIBs
Wavelength (Å)
2018/11/11
Hobbs et al., ApJ, 680, 1256 (2008)

10. DIBs and Present Laboratory Spectrum by CRD
HD204827
300K
C6H5SH
1000V
× High Temperature
○ Rotational Profile
Wavelength (Å)
2018/11/11
Hobbs et al., ApJ, 680, 1256 (2008)

11. Analysis of C6H5S Rotational Profile Simulation of
Non-Boltzmann Distribution
in Diffuse Cloud
Rotational Constants
Simulation of Rotational Profile
in Diffuse Cloud
Comparison with DIBs
2018/11/11

12. Rotational Constants from Rotational Profile
(cm-1)
B3LYP/cc-pVTZ
300K
Wavelength (Å)
2018/11/11
Pgopher

13. Non-Boltzmann Distribution in Diffuse Cloud
Dark Clouds Collision >> Radiation
Diffuse Clouds Less Collision + Radiation
Tk = 100K
Linear Molecule
Oka et al., 2013, ApJ, 773, 42O
Tr = 2.73 K
Tr = 14.6 K
Tr = 80 K
2018/11/11

14. Non-Boltzmann Distribution in Diffuse Cloud
Dark Clouds Collision >> Radiation
Diffuse Clouds Less Collision + Radiation
Tk = 100K
Linear Molecule
Oka et al., 2013, ApJ, 773, 42O
Tr = 2.73 K
Tr = 14.6 K
Tr = 80 K
C2v Asymmetric Top
2018/11/11
Singlet

15. Rotation of C2v Asymmetric Top
J (Kc) Ka
Permanent dipole moment
2018/11/11

16. Boltzmann Distribution
Collision >> Radiation
Dark Clouds
J = 3
J = 2
High temperature
Low temperature
J = 1
J = 0
2018/11/11
Ka = 0
Ka = 1
Ka = 2
Ka = 3

17. Rotation of C2v Asymmetric Top
Diffuse Clouds
Radiative Cooling
a-type
J (Kc) Ka No
Radiative Cooling
Permanent dipole moment
2018/11/11

18. Distribution in Diffuse Cloud
Collision + Radiation (a-type)
Diffuse Clouds
J = 3
DKa = 0
J = 2
High temperature
Low temperature
J = 1
J = 0
2018/11/11
Ka = 0
Ka = 1
Ka = 2
Ka = 3

19. Rotation of C2v Asymmetric Top
Diffuse Clouds
Slow Down
J (Kc) Ka
Hot Axis
Continuous
Rotation
Permanent dipole moment
2018/11/11

20. Analysis of C6H5S Rotational Profile Simulation of
Non-Boltzmann Distribution
in Diffuse Cloud
Rotational Constants
Simulation of Rotational Profile
in Diffuse Cloud
Comparison with DIBs
Pgopher
2018/11/11

21. Rotational Profile in diffuse cloud
2.73 K
Non-Boltzmann distribution is important in diffuse clouds.
HD204827
Collision
40 K
Collision 40 K
Radiation 2.73 K
2018/11/11
Wavelength /Å

22. Distribution in Diffuse Cloud
Collision + Radiation (a-type)
Diffuse Clouds
J = 3
DKa = 0
J = 2
DKa = 2
J = 1
J = 0
2018/11/11
Ka = 0
Ka = 1
Ka = 2
Ka = 3

23. Distribution in Diffuse Cloud
Collision + Radiation (a-type)
Diffuse Clouds
A(DKa = 0) > A(DKa = 2) ~ Collision
The profile can depend on this competition.
2018/11/11

24. Rotational Profile in diffuse cloud
2.73 K
HD204827
Collision 40 K
Radiation 2.73 K
Narrower limit
Wider limit
2018/11/11
Wavelength /Å

25. Comparison with DIBs No fit No detection HD204827 Wavelength /Å
2018/11/11

26. Upper Limit of Column Density
Simulation of Rotational Profile
Band Width of C6H5S: 2Å
Theoretical Calculation (TD–B3LYP / cc–pVTZ)
Oscillator Strength: f = 0.003
HD204827, Hobbs et al., ApJ, 680, 1256 (2008)
Detection threshold: S/N = 5
Upper limit of column density　2×1013 cm-2
2018/11/11

27. Summary By Cavity Ring Down Spectroscopy
Electronic Spectrum of Thiophenoxy Radical C6H5S
By Cavity Ring Down Spectroscopy
Simulation of Rotational Profile in Diffuse Cloud
Upper limit of column density 2×1013 cm-2
Non-Boltzmann distribution is important in diffuse cloud.
2018/11/11

28. 2018/11/11

29. Einstein Coefficients and Oka Coefficient （1973）J
n(J)
B↑r
B↓r A C↓ C↑
J-1
n(J-1)
2018/11/11

30. Rotational Distribution
Linear
Asym top
Radiation temp. (dust) Tr = 40 K
Kinetic (collisional) temp. (H2) Tk = 2.73 K
Oka’s Collisional Coefficient C = 10E-7
Rotational Constant B = 1454 MHz
Permanent Dipole Moment m = 3.1 D
2018/11/11

31. What parameters are determining the rotational profile?
With a hot axis or not.
With a permanent dipole moment or not.
Radiation temperature Tr
Kinetic temperature Tk
C constant
Permanent dipole moment
Rotational constants
Rotational constants difference
Lifetime
2018/11/11