Search for fullerene and fullerane (C 60 H m ) in deep space

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1 Yong Zhang Sun Yat- Sen University The University of Hong Kong Search for fullerene and fullerane (C 60 H m ) in deep space Xiang Tan

2 Material lifecycle in the Galaxy How complex are the molecules that are formed in astronomical environments?

3 Molecules in space (ref. CDMS etc.) 2 atoms 3 atoms 4 atoms 5 atoms 6 atoms 7 atoms 8 atoms 9 atoms 10 atoms 11 atoms 12 atoms >12 atoms H 2 AlF AlCl C 2 CH CH + CN CO CO + CP SiC HCl KCl NH NO NS NaCl OH PN SO SO + SiN SiO SiS CS HF HD FeO? O 2 CF+ SiH? PO AlO OH + CN - SH + SH HCl + TiO ArH + NO +? 11/28/41 C 3 C 2 H C2O C 2 S CH 2 HCN HCO HCO + HCS + HOC + H 2 O H 2 S HNC HNO MgCN MgNC N 2 H + N 2 O NaCN OCS SO 2 SiC 2 CO 2 NH 2 H 3 + SiCN AlNC SiNC HCP CCP AlOH H 2 O + H 2 Cl + KCN FeCN HO 2 TiO 2 C 2 N Si 2 C 8/26/39 c- C 3 H l- C 3 H C 3 N C 3 O C 3 S C 2 H 2 NH 3 HCCN HCNH + HNCO HNCS HOCO + H 2 CO H 2 CN H 2 CS H 3 O + c- SiC 3 CH3 C 3 N - PH 3 HCNO HOCN HSCN H 2 O 2 C 3 H + HMgNC HCCO 2/15/27 C 5 C 4 H C 4 Si l- C 3 H 2 c- C 3 H 2 H 2 CCN CH 4 HC 3 N HC 2 NC HCOOH H 2 CNH H 2 C 2 O H 2 NCN HNC 3 SiH 4 H 2 COH + C 4 H - CNCHO HNCNH CH 3 O NH 4 + H 2 NCO +? NCCNH + 2/13/23 C 5 H l- H 2 C 4 C 2 H 4 CH 3 CN CH 3 NC CH 3 OH CH 3 SH HC 3 NH + HC 2 CHO NH 2 CHO C 5 N l- HC 4 H i- HC 4 N c- H 2 C 3 O H 2 CCNH? C 5 N - HNCHCN 8/17 C 6 H CH 2 CHCN CH 3 C 2 H HC 5 N CH 3 CHO CH 3 NH 2 C 2 H 4 O H 2 CCHOH C 6 H - CH 3 NCO CH 3 C 3 N HCOOCH 3 CH 3 COOH C 7 H C 6 H 2 CH 2 OHCHO l- HC 6 H CH 2 CHCHO? CH 2 CCHCN H 2 NCH 2 CN CH 3 CHNH 5/10 2/11 CH 3 C 4 H CH 3 CH 2 CN (CH 3 ) 2 O CH 3 CH 2 OH HC 7 N C 8 H CH 3 CONH 2 C 8 H - C 3 H 6 CH 3 CH 2 SH? 3/10 CH3C 5 N (CH 3 ) 2 CO (CH 2 OH) 2 CH 3 CH 2 CHO CH 3 CHCH 2 O HC 9 N CH 3 C 6 H C 2 H 5 OCHO CH 3 OCOCH 3? c- C 6 H 6 n- C 3 H 7 CN i- C 3 H 7 CN C 2 H 5 OCH 3? Molecules detected in: ISM (only) Envelopes around evolved stars Planetary nebulae HC 11 N? C 60 C 70 C 60 + Complex aromaxc aliphaxc molecules 195 molecules are idenxfied (or tentaxvely idenxfied) in space, among which 107 are detected in circumstellar envelopes of evolved stars (VY Cma, OH , IRC+10420, IRC+10216, CRL 618, CRL 2688, NGC 7027, Tc 1, etc.). More than 20 molecules are detected towards PNe. 5 1/4 1/4 3/4/4 compounds with 2-13 atoms à molecules with 60- carbon- atomsà C 60 H m?

4 DIBs: indicator of complex compounds in ISM? The DIB carrier is a century- old puzzle. ObservaRons show: DIBs are ubiquitous in diverse astronomical environments DIBs can be classified into a few groups according to their correlaxons. Fullerene family?

The most famous fullerene is C 60, which is arranged as 12 pentagons (5- carbon ring) and 20 hexagons (6- carbon ring).

5 Fullerenes (C 60 ) π- electron cloud 10 Å 7 Å Fullerenes (C 2n+20 ) are molecules composed enxrely of carbon, in the form of a hollow cage. The most famous fullerene is C 60, which is arranged as 12 pentagons (5- carbon ring) and 20 hexagons (6- carbon ring). C 60 is highly symmetric (only four IR- acxve modes.) 1.45Å [5,6] 1.38Å [6,6] C 60 is physically stable because it is the smallest cage with isolated pentagons (C 70 is the second smallest one). C 60 is physically stable and chemically acrve. C 60

6 Fullerene family and derivaxves

7 The discovery of C 60 in laboratory C 60 was discovered experimentally for the first Xme by Kroto et al. (1985, Nature 318, 162). C 60? Laboratory experiments designed to simulate the gas- phase reacxons In carbon star ouhlows C 70 Kroto et al. (1985)

8 Laboratory spectra of C 60 Krätschmer et al. (1990, Nature, 347, 354) developed new technique to effecxvely produce solid state C 60 in laboratory. 217 nm 18.9μm Visible- ultraviolet absorpxon spectra of C 60. IR absorpxon spectra of C μm 7.0μm 8.5μm TheoreXcal spectrum The opxcal spectrum is dominated by a band at 404nm with a few sub- features at nm. 46 degenerated frequencies, 4 of which are IR- acxve.

9 Fullerenes in the Earth and meteorites C 60 and C 70 have been idenrfied in: Carbon- rich Pre- Cambrian rock from Russia (Buseck et al. 1992). Allende meteorite (Becker et al. 1994). Shock- produced breccias of the Sudbury impact structure in Ontario, Canada (Becker et al. 1994). The geological strata of the Cretaceousy- TerXary and the Permian- Trassic boundary layers, associated with bolide impacts (Becker et al. 2000, 2001). C60 can be formed in nature.

10 Search for fullerenes in space - - examples of non- detecxon Electronic transirons of C 60 Snow & Seab (1989) did not detect C 60 in several reddened stars. Herbig (2000) did not detect C 60 features at 3857 and 3980Å in the spectra of O- type stars. Sassara et al. (2001) examined a few objects considered as possible sites of C 60, but did not get posixve detecxon. VibraRonal transirons of C 60 Uncertain detecxons in IRC and I07134 by Clayton (1995) and Kwok et al. (1999) Moutou et al. (1999) did not detect C 60 and C 60 + in the ISO spectrum of NGC 7023 (a reflecxon nebula).

11 Search for fullerenes in space - - C 60+ as carriers of DIBs C 60 has an ionizaxon potenxal of 7.6 ev, and is possibly present as C 60+. The electronic transixons of C 60 + are in the near- IR. Foing & Ehrenfreund (1994, 1997) found that the two near- IR DIBs have wavelengths close to those of C 60 + measured in a neon matrix. DIB This was recently confirmed by Campbell et al. (2015). Three sub- features of C60+ were confirmed by deep spectroscopies (Walker+ 2015; Campbell+ 2016) Gas- phase laboratory spectra of C60+ à C60+ as the first idenrficaron of one of the DIB carriers A doubt was raised by Galazutdinov+ (2017).

Search for IR vibraxonal modes of C 60 - - The first convincing case C 60 and C

Telescope (Cami et al. 2010, Science, 329, 1180) (Cami et al.

12 Search for IR vibraxonal modes of C The first convincing case C 60 and C 70 were for the first Xme detected in a young planetary nebula Tc1 by Spitzer Telescope (Cami et al. 2010, Science, 329, 1180) (Cami et al. 2010) ConXnuum- subtracted Spitzer spectrum of Tc1 Predicted C 60 and C 70 spectra by thermal model

13 C 60 and C 60 + in more objects Circumstellar envelopes surrounding evolved stars: Planetary nebulae with AIBs (GarcÍa- Hernández et al. 2010) Planetary nebulae in the Magellanic Clouds (GarcÍa- Hernández et al. 2011) A proto- planetary nebula (Zhang & Kwok, 2011) Post- AGB stars (Gielen et al. 2011, Roberts et al. 2012) Moderately H- deficient RCB stars (GarcÍa- Hernández et al. 2011) A peculiar binary XX Oph (Evans et al. 2012) DetecRon rate ISMs and Pre- main sequence stars: Two reflecxon nebulae (Sellgren et al. 2010) Orion nebula (Rubin et al. 2011) Young stellar objects and a Herbig Ae/Be star (Roberts et al. 2012) C 60 has been detected in 11 GalacXc PNe, 4 LMC PNe and 7 SMC PNe. The detecxon rate increases with decreasing metallicity (5% in the Milky way, 20% in the LMC, and 44% in the SMC). (GarcÍa- Hernández et al. 2012; Otsuka et al. 2016) VibraXonal transixons of C 60 + are detected in in some of the C 60 sources. (Berne et al. 2013; Strelnikov et al. 2012, 2015; )

14 C 60 in a proto- planetary nebula - - Producer of DIB carrier? Fullerences can be efficiently formed in circumstellar envelopes with a Xmescale of about 1000 years. IRAS C μm C μm C μm C μm Zhang & Kwok (2011) Wavelength (μm) Omont 2016 C 60 + is enhanced in IRAS (Iglesias- Groth & Esposito, 2013). Circumstellar envelops can produce DIB carrier. Two opxcal DIBs are enhanced in C 60 - containing PNe (Diaz- Luis et al. 2015). C 60 derivatives might be DIB carrier. E(B- V) Circumstellar envelopes as the factory producing DIB carriers?

15 Unsolved problems FormaXon routes of fullerene ExcitaXon mechanism of infrared bands

FormaXon of circumstellar C 60 : boyom- up vs.

(boyom- up): - Hydrogen- poor environments at

- Hydrogen- rich at high- temperature (> 3500K).

Tielens 2012) HAC (GarcÍa- Hernández et al.

16 FormaXon of circumstellar C 60 : boyom- up vs. top- down Collisions of small carbon clusters (boyom- up): - Hydrogen- poor environments at normal temperature. - Hydrogen- rich at high- temperature (> 3500K). C chains C 60 DehydrogenaXon of HAC or PAH (top- down): - UV photon- induced. PAH DehydrogenaXon Lost of C Lost of C (Berne & Tielens 2012) HAC (GarcÍa- Hernández et al. 2010; Miceloya et a. 2012) Lost of H Lost of H EjecXon of C 2 by releasing excess energy C 60

AliphaXc/aromaXc organics as the precursor of fullerene? Strong plateaus at 8 and 12 um from aliphaxc components A similar route with that presented by Micelota et al.

17 AliphaXc/aromaXc organics as the precursor of fullerene? Strong plateaus at 8 and 12 um from aliphaxc components A similar route with that presented by Micelota et al. (2012) 3D structure Most of the C60 sources exhibit plateau emission (GarcÍa- Hernández et al. 2012; Zhang & Kwok 2013; Otsuka et al ) Carrier of the exxncxon bump at 2175A (Iglesias- Groth et al. 2003)?

18 ExcitaRon of C 60 IR bands: models vs. observarons One- parameter model is not able to explain the observed intensity raxo. Fluorescence/thermal model Possible causes for the discrepancy: Figure from Brieva et al Uncertain intrinsic strengths Errors in decomposixon of features Other physics processes (such as Poincare fluorescence) ObservaXons Or hydrogenaxon of C 60? (also see Bernard- Salas et al. 2012; Zhang & Kwok 2013).

(Dunk et al. 2013) buckyonion Fullerene- related compounds as DIB carrier?

19 Search for fullerene- related compounds C 60 H m & C 60 H m + (Garcia- Hernandez, Cataldo, Manchado, 2013) CO@C60 H (Omont 2015) Na@C60 (Dunk et al. 2013) buckyonion Fullerene- related compounds as DIB carrier? fullerene compounds DIBs Physically stable ubiquitous Chemically acxve various

20 C- H stretching of C60Hm The first (tentaxve) detecxon of fullerane: ISO SWS m ~ 36? Experiments: C 60 H atoms ( o C) Thermal annealing at 350 o C C 60 H 36 C (550 o C) 60 H 18 (Zhang & Kwok, 2013)

I01005 5-20um spectra of C 60 H m TheoreXcal spectra (B2LYP/BH&HLYP) C 60 IntensiXes of the 4 IR transixons decrease with increasing

21 I um spectra of C 60 H m TheoreXcal spectra (B2LYP/BH&HLYP) C 60 IntensiXes of the 4 IR transixons decrease with increasing hydrogenaxons. à When C60 is heavily hydrogenated, the 4 IR transixons are hardly discovered. C 60 H 2 C 60 H 4 C 60 H 6 C 60 H 36 C 60 C 60 C 60 C 60

22 ExcitaRon of C 60 IR bands: models vs. observarons Fluorescence/thermal model C 60 H C 60 H m hv C 60 + H 2 Figure from Brieva et al observaxons observaxons observaxons Calculated intensity raxos of C 60 H m bands ObservaXons Slight hydrogenaxon can alter the relaxve intensixes of the cage vibraxonal bands. Zhang et al. 2017

23 The 15um feature as a tracer of C60Hm The 15um breath mode is not subject to speciﬁc C60Hm isomers.

24 TheoreXcal intrinsic strength of the 15um feature vs hydrogenaxon degree

25 Search for the 15um feature in C60 astronomical sources C60Hm should exist in a region which is H- atom rich and void of intense UV radiaxon. a possible detecxon NGC 7023

26 Summary Fullerene (C60) has been detected in diverse environments. Fullerene can be efficiently formed in circumstellar envelopes and survive in harsh condixons. Fullerene and its derivaxves might be the carrier of DIBs (a solid case for C 60+ ). Unsolved formaxon and excitaxon problems. We reported a tentaxve detecxon of fullerane (C 60 H m ). C60 and its derivaxves are more common than expected. Solve the problem of scayering C60 band raxos.

27 SpeculaXve conclusion: Fullerene and fullerane are prevalent in space

Molecules in planetary nebulae

Molecules in planetary nebulae Zhang Yong The University of Hong Kong Blowing in the wind conference Vietnam, Aug, 2016 Outline Introduction Gas-phase molecules in planetary nebulae Aromatic/aliphatic