星际多环芳香烃：从芳香性，脂肪性， 到氢化和氘化芳香烃

Presentation on theme: "星际多环芳香烃：从芳香性，脂肪性， 到氢化和氘化芳香烃"— Presentation transcript:

1 星际多环芳香烃：从芳香性，脂肪性， 到氢化和氘化芳香烃
Interstellar PAHs: from Aromacity, Aliphacity, to Superhydrogenation and Deuteration 星际多环芳香烃：从芳香性，脂肪性， 到氢化和氘化芳香烃 杨雪娟 合作者：李爱根, R. Glaser, 钟建新 湘潭

2 星际未证认红外谱带(UIE) UIE 上世纪70年代首次观测到； 载体性质尚不清楚；
主导众多天体的中红外辐射，包括反射星云，行星状星云， HII区，原行星状星云，极亮红外星系等 (Tielens 2008)。 Orion Nebula NGC7331 Spitzer : 8 mm (red); 4.5 mm (green) & 3.6 mm (blue) Tielens (2008)

3 UIE 谱带及起源 Vibration of Hydrocarbons NGC7027 3.3mm sp2  Aromatic
Orion Bar Hony+ (2001) Robertson+(2002); Onaka (2015) 3.3mm sp2  Aromatic 3.4mm sp3  Aliphatic, Superhydrogenation Vibration of Hydrocarbons Tielens (2008)

4 UIE 载体模型 Kwok & Zhang 2011 Yang et al. (2017a)

5 3.4 mm谱征: Aliphacity Yang et al. (2017a)

6 3.4 mm谱征: Aliphacity Yamagish et al. (2012)

7 3.4 mm谱征: Aliphacity 3.4 mm谱征起源： Aliphatic？ Superhydrogenation?
Anharmonicity？ Li & Draine (2012)

8 3.4 mm谱征: Aliphacity 模拟各种星际辐射场下Aliphatic-PAH光谱 (Draine & Li 2001; Draine & Li 2007 ) NC = 24, NC,ali = 0-12;U=1, 102, 104, 106; MMP83, T=6000K, 22000K

9 A3.4/A3.3: Calculated Molecules

10 A3.4/A3.3: Methyl-PAH Yang et al. (2013)

11 A3.4/A3.3:Dimethyl-PAH Yang et al. (2016a)

12 A3.4/A3.3: PAH with Aliphatic Sidegroup
Yang et al. (2016a)

13 A6.85/A6.2:Methyl-PAH0 A6.85 /A6.2~5.0 Yang et al. (2016b)

14 A7.25/A6.2:Methyl-PAH0 A7.25 /A6.2~1.0 Yang et al. (2016b)

15 A6.85/A6.2:Methyl-PAH+ Lower limit ofA6.85 /A6.2~ 0.5
Yang et al. (2016b)

16 A6.85/A6.2:Methyl-PAH+ Lower limit ofA7.25 /A6.2~ 0.25
Yang et al. (2016b)

17 Methyl-PAH 分(离)子光谱 Yang et al. (2017b)

18 Methyl-PAH 分(离)子光谱 分子 离子 MMP83 ISRF Yang et al. (2016b)

19 Methyl-PAH 分(离)子光谱 Yang et al. (2017b)

20 Aliphacity (NC,aliph/NC,arom ) vs. I3.4/I3.3
Yang et al. (2017b)

21 NC,aliph/NC,arom vs. Observed I3.4/I3.3
Yang et al. (2017b)

22 Graphical tool for determining NC,aliph/NC,arom from (I3.4/I3.3)obs
Yang et al. (2017c, in prep)

23 PAH: Superhydrogenation (Hn-PAHs)
Why we care? PAH cations and H-PAH neutrals might act as catalysts for H2 formation (Klarke et al and reference therein) Showing a mixture of both aromatic and aliphatic spectra characteristics (Sandford et al. 2013) Present/Abundant in benign environment such as PPN (Bernstein et al. 1996) , dense molecular clouds (Sandford et al. 2000; 2013)

24 PAH: Superhydrogenation (Hn-PAHs)
How we know? Experiment (Bernstein+ 1996; Sandford ) Theoretical Calculation (Pauzat ; ) Sandford + (2013)

25 PAH: Superhydrogenation
Yang et al. (2017d, to be submitted)

26 结果: DHN光谱

27 结果: OHN光谱

28 计算结果：A3.4/A3.3 A3.4/A3.3 = 1.6 I3.4/I3.3 = 0.12 NC-HH/NC-H< 3%

29 PAH: Deuteration Why we care?
The amount of deuterium in a galaxy provides a direct measure of cosmic nucleosynthesis and is related to the chemical evolution of the galaxy itself. The large size (>50 C atoms) and numerous hydrogen atoms of interstellar PAHs allows them to potentially be a large reservoir of deuterium in the ISM (Allamandola et al. 1989; Tielens 1992; Hudgins et al. 2004). Deuterium atoms can replace hydrogen atom in PAHs and can participate in the same characteristic vibrational modes (Bauschlicher et al. 1997).

30 DPAH: Formation Draine (2006)

31 PAH: Deuteration How to proceed? Experiment (Sandford+ 2000)
Theoretical Calculation (Hudgins ; Buragohain ; ) Observation (Bernstein+ 1996; Peeters+ 2004; Linsky ; Doney )

32 DPAH: Calculation DPAH HPAH Hudgins (2004)

33 DPAH: Calculation Buragohain+ （2015）

34 DPAH: Observation No evidence of large amount of deuterated PAHs  JWST?! Onaka et al. (2015)

35 DPAH: Our Work Yang et al. (2017e, in prep)

36 DPAH Spectra: 1D-Benzene
C-D bending C-D stretch

37 PAD Spectra: 1D-Naph C-D bending C-D stretch

38 PAD Spectra: nD-Pyrene
C-D stretch C-H stretch D

39 Results: A4.4 & A3.3

40 Results: A4.4/A3.3

41 Future Perspective