Origin of diffuse interstellar lines

Douglas, A. E.

doi:10.1038/269130a0

Cited by 301 publications

(143 citation statements)

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“…Only in the case of C 3 could very weak interstellar absorptions be detected and the species unambiguously identified in the diffuse medium [5]. The analyses of these data led to the conclusion that Douglas' hypothesis [2] is now excluded; carbon chains comprising up to a dozen atoms or their hydrogen containing analogues C n H cannot be the carriers of the stronger DIBs [6]. In turn, this pointed to future studies of potential carriers; apart from having electronic transitions in the optical regions, the oscillator strengths would have to be two orders of magnitude larger than the afore-mentioned chains.…”

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confidence: 90%

“…Following the suggestion by Douglas [2] that bare carbon chains comprising a handful or two of carbon atoms are good candidates as carriers of these absorptions-the diffuse interstellar bands (DIBs)-it took around 20 years to obtain a number of gas-phase electronic spectra in the laboratory [3]. Thus, it became possible for the first time to make a direct comparison with the astronomical data under comparable conditions: collision-free environment and low, 10 -50 K, temperatures.…”

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confidence: 99%

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Electronic spectra of C₆H⁺ and C₆H₃⁺ in the gas phase

Raghunandan

Mazzotti

Maier

2010

J. Am. Soc. Mass Spectrom.

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Measurement of the 3 ⌸ Ϫ 3 ⌸ transition of C 6 H ϩ in the gas phase near 19486 cm Ϫ1 is reported. The experiment was carried out with a supersonic slit-jet expansion discharge using cavity ringdown absorption spectroscopy. Partly resolved P lines and observation of band heads permitted a rotational contour fit. Spectroscopic constants in the ground and excited-state were determined. The density of ions being sampled is merely 2 ϫ 10 8 cm Ϫ3 . Broadening of the spectral lines indicates the excited-state lifetime to be Ϸ100 ps. The electronic transition of HC 6 H 2 ϩ at 26402 cm Ϫ1 assumed to be 1 A 1 Ϫ X 1 A 1 in C 2v symmetry could not be rotationally resolved. (J Am Soc Mass Spectrom 2010, 21, 694 -697)

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confidence: 90%

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confidence: 99%

Electronic spectra of C₆H⁺ and C₆H₃⁺ in the gas phase

Raghunandan

Mazzotti

Maier

2010

J. Am. Soc. Mass Spectrom.

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“…Electronic transitions in carbon clusters have been proposed as possible candidates for the diffuse interstellar bands. 3,4,17,18 This has motivated Maier and co-workers [19][20][21][22] to study the ultraviolet (UV) and visible absorption spectroscopy of mass-selected carbon clusters deposited in a cryogenic matrix, obtaining vibrationally resolved electronic transitions for C 4 , C 5 , and C 6 . Further information on excited electronic states comes from anion photoelectron spectroscopy, [14][15][16] which reveals states that are optically inaccessible from the neutral ground state, and electronic structure calculations.…”

Section: Introductionmentioning

confidence: 99%

Photodissociation of Linear Carbon Clusters C_n (n = 4−6)

et al. 2000

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The photodissociation of mass-selected linear carbon clusters (C n , n ) 4-6) is studied using fast beam photofragment translational spectroscopy. The photofragment yield (PFY) spectra consist of several continua spanning the whole visible and ultraviolet region. The product mass distributions for dissociation of C n clusters are dominated by C 3 and its partner fragment C n-3 , although some minor channels are also identified for dissociation of C 4 and C 5 clusters. Translational energy P(E T ) distributions for the C 3 + C n-3 channel were measured at several photolysis energies. The PFY spectra and P(E T ) distributions indicate that multiphoton dissociation occurs at photon energies below the dissociation threshold and that both single-photon and multiphoton dissociation occur above the threshold. The one-photon components of the P(E T ) distributions can be modeled by phase space theory (PST), suggesting that photoexcitation is followed by internal conversion to the ground state. The PST analysis yields dissociation energies for C n f C 3 + C n-3 in reasonable agreement with recent Knudsen effusion mass spectrometry measurements.

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“…Furthermore, while the neutrals do not possess electronic transitions in the visible (these lie below 300 nm), their ions do (Jochnowitz & Maier 2008). Thus the hypothesis concerning smaller carbon chains (Douglas 1977) has been tested and can now be rejected (Maier et al 2004).…”

Section: Introductionmentioning

confidence: 99%

“…With the laboratory gas-phase spectra in hand, comparisons with astronomical observations were undertaken (Motylewski et al 2000). Because the selected species given above have absorptions in the 400-1,000 nm region of the diffuse interstellar bands (DIBs) (Snow & McCall 2006), it proved possible to test directly for the first time the proposition that carbon chains of the size C n n = 5-10 are good candidates as carriers (Douglas 1977). Such comparisons showed that these, and related molecules such as polar chains with hydrogen C n H, can not be responsible for the stronger DIBs (Maier et al 2004).…”

Section: Introductionmentioning

confidence: 99%

Electronic spectra of carbon chains and rings: Astrophysical relevance?

Jochnowitz

Maier

2008

Proc. IAU

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Abstract. Our research has focused on the measurement of the electronic spectra of unstable molecules which are presumed to be of relevance to astrophysical observations. Among these are the carbon chains and their ions. Thus we have been using and developing a number of spectroscopic methods to determine their spectra in the gas phase, including absorption via cavity ring-down and REMPI methods. The species are produced in supersonic jets coupled with discharge and laser ablation sources. With the successful laboratory detection of the electronic spectra of a number of key species, such as bare carbon chains C n n=4,5, comparisons with astrophysical data could be made which lead to interesting implications for the future search for the species which could be responsible for the diffuse interstellar bands. Among the recent relevant observations in the laboratory have been the electronic spectra of carbon rings, C n n=14,18,22, the development of a method to study transitions in mass-selected ions collisionally relaxed to 20 K and held in a 22-pole radiofrequency trap, and the study of metal containing carbon chains.

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Origin of diffuse interstellar lines

Cited by 301 publications

References 11 publications

Electronic spectra of C₆H⁺ and C₆H₃⁺ in the gas phase

Electronic spectra of C₆H⁺ and C₆H₃⁺ in the gas phase

Photodissociation of Linear Carbon Clusters C_n (n = 4−6)

Electronic spectra of carbon chains and rings: Astrophysical relevance?

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Origin of diffuse interstellar lines

Cited by 301 publications

References 11 publications

Electronic spectra of C6H+ and C6H3+ in the gas phase

Electronic spectra of C6H+ and C6H3+ in the gas phase

Photodissociation of Linear Carbon Clusters Cn (n = 4−6)

Electronic spectra of carbon chains and rings: Astrophysical relevance?

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Electronic spectra of C₆H⁺ and C₆H₃⁺ in the gas phase

Electronic spectra of C₆H⁺ and C₆H₃⁺ in the gas phase

Photodissociation of Linear Carbon Clusters C_n (n = 4−6)