The formation and destruction of doubly-charged polycyclic aromatic hydrocarbon cations in the interstellar medium

1986 ◽  
Vol 41 (2) ◽  
pp. 427-438 ◽  
Author(s):  
Sydney Leach
Science ◽  
2018 ◽  
Vol 359 (6372) ◽  
pp. 202-205 ◽  
Author(s):  
Brett A. McGuire ◽  
Andrew M. Burkhardt ◽  
Sergei Kalenskii ◽  
Christopher N. Shingledecker ◽  
Anthony J. Remijan ◽  
...  

Polycyclic aromatic hydrocarbons and polycyclic aromatic nitrogen heterocycles are thought to be widespread throughout the universe, because these classes of molecules are probably responsible for the unidentified infrared bands, a set of emission features seen in numerous Galactic and extragalactic sources. Despite their expected ubiquity, astronomical identification of specific aromatic molecules has proven elusive. We present the discovery of benzonitrile (c-C6H5CN), one of the simplest nitrogen-bearing aromatic molecules, in the interstellar medium. We observed hyperfine-resolved transitions of benzonitrile in emission from the molecular cloud TMC-1. Simple aromatic molecules such as benzonitrile may be precursors for polycyclic aromatic hydrocarbon formation, providing a chemical link to the carriers of the unidentified infrared bands.


2006 ◽  
Vol 460 (2) ◽  
pp. 519-531 ◽  
Author(s):  
M. Rapacioli ◽  
F. Calvo ◽  
C. Joblin ◽  
P. Parneix ◽  
D. Toublanc ◽  
...  

1996 ◽  
Vol 74 (7-8) ◽  
pp. 407-410 ◽  
Author(s):  
K. Iwata ◽  
R. G. Greaves ◽  
C. M. Surko

The annihilation of positrons in a simulated interstellar medium consisting of molecular hydrogen and a small admixture of the polycyclic aromatic hydrocarbon, naphthalene, was studied in a Penning trap containing cold positrons. The experiments demonstrate the ability to distinguish two distinct components in the annihilation γ-ray spectra. The significance of the experiment for the analysis of γ-ray spectra of astrophysical origin is discussed.


2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Michael Gatchell ◽  
João Ameixa ◽  
MingChao Ji ◽  
Mark H. Stockett ◽  
Ansgar Simonsson ◽  
...  

AbstractLaboratory studies play a crucial role in understanding the chemical nature of the interstellar medium (ISM), but the disconnect between experimental timescales and the timescales of reactions in space can make a direct comparison between observations, laboratory, and model results difficult. Here we study the survival of reactive fragments of the polycyclic aromatic hydrocarbon (PAH) coronene, where individual C atoms have been knocked out of the molecules in hard collisions with He atoms at stellar wind and supernova shockwave velocities. Ionic fragments are stored in the DESIREE cryogenic ion-beam storage ring where we investigate their decay for up to one second. After 10 ms the initially hot stored ions have cooled enough so that spontaneous dissociation no longer takes place at a measurable rate; a majority of the fragments remain intact and will continue to do so indefinitely in isolation. Our findings show that defective PAHs formed in energetic collisions with heavy particles may survive at thermal equilibrium in the interstellar medium indefinitely, and could play an important role in the chemistry in there, due to their increased reactivity compared to intact or photo-fragmented PAHs.


2019 ◽  
Author(s):  
Yachu Du ◽  
Kyle Plunkett

We show that polycyclic aromatic hydrocarbon (PAH) chromophores that are linked between two five-membered rings can access planarized structures with reduced optical gaps and redox potentials. Two aceanthrylene chromophores were connected into dimer model systems with the chromophores either projected outward (2,2’-biaceanthrylene) or inward (1,1’-biaceanthrylene) and the optical and electronic properties were compared. Only the planar 2,2’-biaceanthrylene system showed significant reductions of the optical gaps (1 eV) and redox potentials in relation to the aceanthrylene monomer.<br>


2019 ◽  
Author(s):  
Yachu Du ◽  
Kyle Plunkett

We show that polycyclic aromatic hydrocarbon (PAH) chromophores that are linked between two five-membered rings can access planarized structures with reduced optical gaps and redox potentials. Two aceanthrylene chromophores were connected into dimer model systems with the chromophores either projected outward (2,2’-biaceanthrylene) or inward (1,1’-biaceanthrylene) and the optical and electronic properties were compared. Only the planar 2,2’-biaceanthrylene system showed significant reductions of the optical gaps (1 eV) and redox potentials in relation to the aceanthrylene monomer.<br>


2016 ◽  
Vol 9 (1) ◽  
pp. 64-72
Author(s):  
Fauziati Fauziati ◽  
Eldha Sampepana

Palm shell liquid smoke obtained by pyrolysis and redestilasi still produce a pungent smoke flavor and color of yellow to brownish yellow so that the necessary research purification of smoke that can be used as ingredients other than preservatives, such as antiseptic hand wash. The research objective is to reduce the stinging liquid smoke aroma, color is tawny and to identify the characterization of the active components of liquid smoke shell oil refining results in Gas Chromatography Mass Spectrometry (GC-MS). The purification process of liquid smoke with redistilled at a temperature of 2000C and by adding 4.5% zeolite adsorbent made three (3) times the resulting liquid smoke of distillate and residue. Liquid smoke produced from distillate and residue are added activated charcoal as much as 9%, 10.5% and 12%, then stirred with a shaker subsequently allowed to stand for 6 days and 10 days The results of the study showed that liquid smoke purification results of the residue by the addition of activated charcoal as 12% and the time saved for 10 days (A2B2C3) gives flavor and color by 1.94 of 1.84 is odorless, yellowish white color and clarity. While the characteristics of the active components of purification results are predominantly acetic acid and phenol compounds of residues that serve as preservatives, antibacterial and antioxidant compounds while PAH (Polycyclic Aromatic Hydrocarbon), namely tar, benzoperen, gualakol and siringoll (aroma causes) undetectedABSTRAKAsap cair cangkang sawit yang diperoleh melalui proses pirolisis dan redestilasi masih menghasilkan aroma asap menyengat dan warna kuning hingga kuning kecoklatan sehingga diperlukan penelitian pemurnian asap yang dapat digunakan sebagai bahan lain selain pengawet, seperti antiseptik pencuci tangan. Tujuan penelitian adalah  untuk mengurangi aroma asap cair yang menyengat, warna yang masih kuning kecoklatan dan untuk  mengidentifikasi karakterisasi komponen aktif asap cair cangkang sawit hasil pemurnian secara Kromatografi Gas Spektrometri Massa (GC-MS). Proses  pemurnian asap cair dengan  redistilasi pada suhu 2000C dan dengan menambahkan adsorben zeolit 4,5% yang dilakukan sebanyak 3 (tiga) kali  dihasilkan asap cair dari Destilat dan Residu . Asap cair  yang dihasilkan dari destilat dan residu ditambahkan arang aktif sebanyak 9%,10,5% dan 12%  kemudian diaduk dengan shaker selanjutnya didiamkan selama 6 hari dan 10 hari .Hasil penelitian menunjukkan bahwa asap cair hasil pemurnian dari residu dengan penambahan arang aktif sebanyak 12% dan waktu simpan selama 10 hari ( A2B2C3 ) memberikan aroma sebesar 1,94 dan warna sebesar 1,84 adalah tidak berbau ,  warna putih kekuningan dan jernih . Sedangkan  karakteristik  komponen aktif hasil pemurnian yang paling dominan  adalah  senyawa acetic acid dan phenol  dari residu yang berfungsi sebagai bahan pengawet, antibakteri dan antioksidan sedangkan senyawa PAH (Polycyclic Aromatic Hydrocarbon) yaitu tar, benzoperen,  gualakol  dan siringoll ( penyebab aroma ) tidak terdeteksi . Kata kunci : asap cair, cangkang sawit, komponen aktif, pemurnian, redestilasi 


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