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 2017.6.28 @ 湘潭
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)
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)
UIE 载体模型 Kwok & Zhang 2011 Yang et al. (2017a)
3.4 mm谱征: Aliphacity Yang et al. (2017a)
3.4 mm谱征: Aliphacity Yamagish et al. (2012)
3.4 mm谱征: Aliphacity 3.4 mm谱征起源： Aliphatic？ Superhydrogenation? Anharmonicity？ Li & Draine (2012)
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
A3.4/A3.3: Calculated Molecules
A3.4/A3.3: Methyl-PAH Yang et al. (2013)
A3.4/A3.3:Dimethyl-PAH Yang et al. (2016a)
A3.4/A3.3: PAH with Aliphatic Sidegroup Yang et al. (2016a)
A6.85/A6.2:Methyl-PAH0 A6.85 /A6.2~5.0 Yang et al. (2016b)
A7.25/A6.2:Methyl-PAH0 A7.25 /A6.2~1.0 Yang et al. (2016b)
A6.85/A6.2:Methyl-PAH+ Lower limit ofA6.85 /A6.2~ 0.5 Yang et al. (2016b)
A6.85/A6.2:Methyl-PAH+ Lower limit ofA7.25 /A6.2~ 0.25 Yang et al. (2016b)
Methyl-PAH 分(离)子光谱 Yang et al. (2017b)
Methyl-PAH 分(离)子光谱 分子 离子 MMP83 ISRF Yang et al. (2016b)
Methyl-PAH 分(离)子光谱 Yang et al. (2017b)
Aliphacity (NC,aliph/NC,arom ) vs. I3.4/I3.3 Yang et al. (2017b)
NC,aliph/NC,arom vs. Observed I3.4/I3.3 Yang et al. (2017b)
Graphical tool for determining NC,aliph/NC,arom from (I3.4/I3.3)obs Yang et al. (2017c, in prep)
PAH: Superhydrogenation (Hn-PAHs) Why we care? PAH cations and H-PAH neutrals might act as catalysts for H2 formation (Klarke et al. 2013 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)
PAH: Superhydrogenation (Hn-PAHs) How we know? Experiment (Bernstein+ 1996; Sandford + 2013) Theoretical Calculation (Pauzat + 1999; ) Sandford + (2013)
PAH: Superhydrogenation Yang et al. (2017d, to be submitted)
结果: DHN光谱
结果: OHN光谱
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%
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).
DPAH: Formation Draine (2006)
PAH: Deuteration How to proceed? Experiment (Sandford+ 2000) Theoretical Calculation (Hudgins + 2004; Buragohain + 2015; ) Observation (Bernstein+ 1996; Peeters+ 2004; Linsky + 2006; Doney + 2016)
DPAH: Calculation DPAH HPAH Hudgins (2004)
DPAH: Calculation Buragohain+ （2015）
DPAH: Observation No evidence of large amount of deuterated PAHs JWST?! Onaka et al. (2015)
DPAH: Our Work Yang et al. (2017e, in prep)
DPAH Spectra: 1D-Benzene C-D bending C-D stretch
PAD Spectra: 1D-Naph C-D bending C-D stretch
PAD Spectra: nD-Pyrene C-D stretch C-H stretch D
Results: A4.4 & A3.3
Results: A4.4/A3.3
Future Perspective