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REVIEW 3 major objections 5 minor 235 references

Hexahydropyrene — pyrene with six extra hydrogens — is proposed as the carrier of the 3.403 µm red component of the 3.4 µm interstellar emission band, established through new gas-phase spectra and cooling-cascade modeling.

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2026-08-01 21:34 UTC pith:ZHQKV6LC

load-bearing objection Read this for the laboratory spectra and anharmonicity fits, which are solid and reusable; treat the 6H-pyrene identification of the 3.403 µm band as a plausible hypothesis that still depends on untested dissociation energy and scaling choices. the 3 major comments →

arxiv 2607.16018 v1 pith:ZHQKV6LC submitted 2026-07-17 astro-ph.GA

Infrared spectroscopy of gas-phase hydrogenated and methylated pyrenes: from laboratory spectra to the simulated 3.4 μm emission band

Karine Demyk , Christine Joblin , Louan de Bentzmann , Dominique Toublanc , Giacomo Mulas This is my paper
classification astro-ph.GA
keywords aromatic infrared bands3.4 µm emission bandhexahydropyrenesuperhydrogenated PAHsanharmonicityISM: lines and bandsastrochemistrygas-phase infrared spectroscopy
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper argues that a specific molecule, 1,2,3,6,7,8-hexahydropyrene (6H-pyrene), is the carrier of the 3.403 µm red component of the 3.4 µm aromatic infrared band observed toward the Orion Bar and NGC 1333. The case rests on new gas-phase laboratory spectra of pyrene and its hydrogenated and methylated derivatives at 373–673 K, from which the shifts and broadenings of each infrared band with temperature are extracted as empirical anharmonicity laws. These laws are then attached to a Monte Carlo model of the cooling cascade that follows absorption of a single UV photon, converting static absorption spectra into synthetic emission spectra. In that model, a 6H-pyrene excited by a ~4 eV photon emits an aliphatic CH-stretch band at 3.403 µm that reproduces the observed profile, whereas 1-methylpyrene contributes mainly to the 3.3 µm band and the 3.3–3.6 µm plateau. If correct, the result assigns a long-debated satellite band to superhydrogenated PAHs and implies that the 3.4-to-3.3 µm band ratio is only a rough tracer of superhydrogenation.

Core claim

On the authors' own terms, the central result is that the cooling cascade of gas-phase 6H-pyrene after absorption of a ~4 eV UV photon produces an aliphatic CH-stretch emission band at 3.403 µm, matching the red component of the 3.4 µm AIB toward the Orion Bar and NGC 1333. The match comes from attaching empirically measured temperature laws for band position and width, derived from 373–673 K gas-phase spectra, to every photon emitted in a Monte Carlo simulation of the microcanonical cooling cascade. The peak that does the work is the aliphatic asymmetric in-plane CH2 stretch near 2943 cm⁻¹ (3.398 µm at 473 K), which red-shifts with temperature into the observed position. The paper proposes

What carries the argument

The load-bearing input is the set of empirical anharmonicity laws ν(T) = χ′0 + χ′1·T and Δν(T) = χ″0 + χ″1·T, extracted by fitting gas-phase spectra of pyrene, 2H-, 4H-, 6H-pyrene, and methylpyrene at 373–673 K (rotational broadening subtracted) with pseudo-Voigt components. These linear laws quantify how each CH-stretch band shifts and widens as the molecule heats. The second half is a Monte Carlo emission code that simulates thousands of UV-photon absorption and cooling cascades, computes the temperature at which each photon is emitted, and assigns the anharmonicity-corrected position and width to that photon. Together they turn static laboratory absorption spectra into temperature-resolve

Load-bearing premise

The identification collapses if the linear temperature shifts of band position and width, measured in the laboratory only up to 673 K, do not continue to hold at the ~1000 K internal temperatures at which a 4 eV-excited 6H-pyrene emits its 3.4 µm photons — or if the neutral molecule does not survive a 4 eV photon as assumed from the cation's ~5 eV dissociation energy.

What would settle it

Measure the aliphatic CH-stretch band of 6H-pyrene at gas-phase temperatures above 800 K, ideally in UV-excited emission, and check whether it actually sits at 3.403 µm at the temperatures reached during the cooling cascade; separately, measure the dissociation threshold of neutral 6H-pyrene. If the band lands elsewhere at those temperatures, or if the neutral molecule dissociates below ~4 eV, the proposed match to the observed 3.403 µm component fails.

Watch this falsifier — get emailed when new claim-graph text bears on it.

If this is right

  • If the identification holds, the 3.403 µm component of the 3.4 µm band becomes a specific signature of superhydrogenated PAHs (6H-pyrene-like molecules) rather than of methylated PAHs.
  • The 3.4-to-3.3 µm band ratio is at best an approximate tracer of superhydrogenation, since only the 3.403 µm component is tied to aliphatic content while the carrier of the 3.395 µm component remains unknown.
  • 6H-pyrene emission should be confined to shielded regions where ~4 eV photons can excite the molecule without dissociating it, consistent with the observed association of the 3.403 µm band with H2 emission in PDRs.
  • When the simulated spectra are scaled to the CH-stretch region, no strong unaccounted-for features appear elsewhere in the 3–14 µm range, so the assignment does not conflict with existing Orion Bar observations.
  • The released laboratory spectra and anharmonicity parameters give future work the input data needed to model hydrogenated and methylated PAH emission in other environments, from protoplanetary disks to external galaxies.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • Beyond the paper: the 3.403 µm band is likely carried by a family of superhydrogenated PAHs sharing the same CH2 asymmetric-stretch motif, not by 6H-pyrene alone; a decisive test is to search the same JWST spectra for 6H-pyrene's other strong bands (CH2 scissoring near 6.9 µm, CH2 bending near 7.4–7.9 µm).
  • Beyond the paper: the identification is not unique — the modeled match is scaled to the observations by an arbitrary factor and alternative carriers are not quantitatively excluded, so the claim stands as a proposal pending a search for corroborating or conflicting features.
  • Beyond the paper: the observed 3.403 µm position should drift with local radiation field strength if the extrapolated anharmonicity laws are correct; mapping the band position across a PDR would test the extrapolation directly.
  • Beyond the paper: the same empirical-anharmonicity-plus-cooling-cascade recipe could be applied to the 6.2 and 7.7 µm AIBs of hydrogenated PAHs, whose hot-band structure is also temperature-sensitive, potentially linking more AIB substructure to superhydrogenation.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit.

Referee Report

3 major / 5 minor

Summary. The paper presents new gas-phase mid-infrared absorption spectra (1.4–25 µm) of pyrene, a set of hydrogenated pyrenes (2H-, 4H-, 6H-pyrene), and 1-methylpyrene at temperatures between 373 and 673 K. From these spectra the authors derive empirical linear anharmonicity laws for band positions and widths, correct for rotational broadening, and embed them in a Monte Carlo emission model to compute anharmonic emission spectra after UV-photon absorption. The simulated spectra are compared with JWST observations of the Orion Bar and with older NGC 1333 data. The central claim is that 1,2,3,6,7,8-hexahydropyrene (6H-pyrene) excited by a ~4 eV photon can account for the 3.403 µm component of the 3.4 µm AIB, while 1-methylpyrene contributes mainly to the underlying plateau. The experimental data and derived parameters are made publicly available in the CosmicPAH-IRDB database.

Significance. If substantiated, this work would provide the most detailed spectral match to date for the 3.403 µm emission component, a specific superhydrogenated PAH carrier, and would refine the interpretation of the 3.4/3.3 µm intensity ratio in astrophysical environments. The experimental dataset is a significant resource: gas-phase spectra of hydrogenated and methylated pyrenes over a wide temperature range, with documented fitting uncertainties, rotational-broadening corrections, and public availability of spectra and anharmonicity parameters. The authors are also commendably explicit about several limitations of their method, including temperature extrapolation, blending, and unphysical negative fitted widths. However, the astronomical identification rests on a few load-bearing assumptions that are not yet fully tested, as detailed below.

major comments (3)
  1. [§4.2] The excitation energy of 4 eV for 6H-pyrene is selected because the 3.8–4.5 eV absorption band is ~10× weaker than the 5.5–5.7 eV band, but the survival of the neutral molecule at 4 eV is assumed by adopting the cation dissociation energy (~5 eV, Stockett et al. 2021). No neutral D0 is measured or computed. If D0(6H-pyrene) < 4 eV, the molecule dissociates before emitting the 3.4 µm photons, and the synthetic spectra in Figs. 6–7 are inapplicable. This assumption is explicitly stated in §4.2 ('we assume similar dissociation energies for their neutral counterparts') and is load-bearing for the central identification. Please provide a measurement or a quantum-chemical estimate of the neutral dissociation threshold, or at minimum a sensitivity test at a lower excitation energy (e.g., 3.5 eV) and a discussion of how the 3.403 µm match would change.
  2. [Fig. 6] The comparison with observations uses arbitrary scaling factors: 2.1×10^-6 for 6H-pyrene and 3.5×10^-6 for Me-pyrene, with no column-density or abundance check. The match therefore only tests spectral morphology, not whether the proposed carriers can plausibly produce the observed intensity. The manuscript itself states in §5 that 'it remains to be demonstrated whether 6H-pyrene is the only candidate satisfying spectral constraints', which is an explicit admission that uniqueness is not established. Please derive the required column density and abundance of 6H-pyrene (and Me-pyrene) implied by these scaling factors and compare with astrochemical upper limits or expectations; alternatively, explicitly frame the identification as tentative on abundance grounds.
  3. [§4.3, Table 4] The empirical anharmonicity laws are derived over 423–673 K, but the 3.4 µm emission occurs at higher temperatures during the cooling cascade (Fig. B.2). The paper acknowledges in §4.3 that extrapolation is 'necessitate[d]', and relies on linear extrapolations justified by molecular dynamics simulations for pyrene (Chakraborty et al. 2021). However, Table 4 shows piecewise linear fits with breaks at 523/623 K for 6H-pyrene, and the high-temperature segments are used beyond the measured range. Since the central match to 3.403 µm depends on the band position at the hottest emission temperatures, this extrapolation is a load-bearing point. Please provide a sensitivity analysis (e.g., using alternative high-T extrapolations, propagating the uncertainties of χ'1 and χ''1) or soften the 'high accuracy' claim in §5.
minor comments (5)
  1. [Abstract] Typo: 'tehtrahydropyrene' should be 'tetrahydropyrene'; also 'polycylic' should be 'polycyclic'. The abstract ends with 'Conclusions..' (double period).
  2. [Table 4] The note states that negative χ''1 values result in 'unphysical band widths'. This is acknowledged, but the table would be clearer if those entries were flagged with a dedicated symbol and if the text explained how the emission model treats them beyond 'refrained from extrapolating'.
  3. [Appendix A] The sentence listing rotational broadening values contains a typo: '.6.5' should be '6.5'.
  4. [Fig. 7] The upper panel compares with the 'difference of the normalised DF3 and aPDR spectra', but the text of §5 refers to 'the difference spectrum between the DF3 and atomic positions'. Please define 'aPDR' and ensure the terminology is consistent between text and caption.
  5. [§2.2] The code name appears as both 'AnharmoniCaOs' and 'AnharmoniCaOscalculations'; use a consistent rendering.

Circularity Check

0 steps flagged

No significant circularity: the 3.403 µm comparison is an external benchmark, not an input to the laboratory fits or the emission model.

full rationale

The paper's derivation chain is a forward model. Laboratory absorption spectra of 6H-pyrene and Me-pyrene at 373–673 K are fitted to obtain empirical anharmonicity laws ν(T) and Δν(T) (§2.3, Table 4). These laws are then used in a Monte Carlo cooling-cascade code (§2.4) to assign band positions and widths to photons emitted after absorption of a UV photon, and the resulting synthetic spectra are compared with JWST Orion Bar and NGC 1333 observations (§4.2, §5, Figs. 6–7). The astronomical 3.403 µm component is not an input to the anharmonic fits, the band-intensity list, or the Monte Carlo code; it is an external benchmark. The choice of 4 eV for 6H-pyrene is motivated by the molecule's photo-absorption bands and the assumed, explicitly flagged cation-based dissociation energy (§4.2), and the paper acknowledges the need to extrapolate anharmonicity laws beyond the measured 423–673 K range (§4.3). These are accuracy and robustness limitations, not circular reductions: the match is not equivalent to the inputs by construction. Arbitrary scaling of the synthetic spectra (§5, Fig. 6) weakens abundance claims but does not affect the position/profile comparison used for the carrier identification. No load-bearing self-citation chain or imported uniqueness theorem is invoked; prior work (Bernstein et al. 1996; Joblin et al. 1995, 1996a; Pech et al. 2002) is used as methodology or independent observational/laboratory precedent, not as the sole justification of the carrier claim.

Axiom & Free-Parameter Ledger

5 free parameters · 6 axioms · 0 invented entities

The central identification does not invent new physics, but it relies on a chain of fitted and assumed inputs: lab-fitted anharmonicity laws extrapolated in temperature, a selected photon energy, assumed neutral dissociation energies, and arbitrary comparison scaling. These do not by themselves invalidate the proposal but limit the independence of the final match.

free parameters (5)
  • Per-band anharmonicity coefficients χ'1 and χ''1 (temperature slopes of position and width) = Table 4: e.g. 6H-pyrene 3.398 µm band χ'1 = -0.85e-2 to -1.15e-2 cm^-1 K^-1; several heavily blended bands have negative
    Fitted to laboratory spectra at 423-673 K; these coefficients are the core empirical input to the emission model.
  • Rotational broadening correction = 5.9-6.9 cm^-1 over 423-673 K, averaged from three pyrene bands
    Estimated from P-Q-R branch fits and subtracted from all bands; the paper acknowledges this is a first approximation applied to all species.
  • Representative absorbed photon energy = 4 eV for 6H-pyrene, 6 eV for Me-pyrene
    Selected for comparison with astronomical spectra after the simulations were produced; balances photoabsorption and assumed stability but is a post-hoc choice.
  • Arbitrary scaling factors for simulated-vs-observed comparison = 2.1e-6 (6H-pyrene), 3.5e-6 or 3.6e-6 (Me-pyrene, inconsistent between Fig. 6 and Fig. G.1)
    The synthetic spectra are scaled by hand to match observed intensities; no absolute column densities are derived.
  • Constant widths for uncharacterized Me-pyrene bands = 36.18, 25.63, 16.80, 19.85, 40.25, 33.90, 40.40 cm^-1 for bands at 963-1597 cm^-1
    No anharmonicity functions were derived for these weak bands; fixed widths are adopted in the model.
axioms (6)
  • domain assumption Anharmonicity functions measured at 423-673 K can be linearly extrapolated to the higher temperatures of 3.4 µm emission.
    Sect. 4.3: limitations necessitate extrapolation; linear extrapolation is stated to be consistent with molecular dynamics simulations (Chakraborty et al. 2021), but the target temperatures are outside the measured range.
  • domain assumption Neutral 6H-pyrene and Me-pyrene dissociation energies equal the measured cation values (~5 eV and ~6 eV).
    Sect. 4.2: 'we assume similar dissociation energies for their neutral counterparts'; no direct neutral measurements are presented.
  • domain assumption Photoabsorption spectra recorded in Ne matrices approximate the gas-phase UV absorption of the neutral molecules.
    Sect. 4.2 uses Halasinski et al. (2005) and unpublished data to set the excitation/dissociation balance.
  • domain assumption Rotational broadening estimated from three pyrene bands applies to all bands and species after subtraction.
    Appendix A: 'As a first approximation, we assume these values apply to all bands and species'.
  • domain assumption B3LYP-D3 DFT harmonic/anharmonic calculations provide reliable mode assignments and relative intensities.
    Sect. 2.2; a standard quantum-chemical approximation, validated by comparison with gas-phase spectra in Sect. 3.1.
  • domain assumption A harmonic Monte Carlo cooling cascade plus empirical anharmonic band shifts and widths reproduces the emitted IR spectrum.
    Sect. 2.4: anharmonic corrections in state counts are stated to be negligible, with the primary anharmonicity coming from the empirical parameters.

pith-pipeline@v1.3.0-alltime-deepseek · 22600 in / 12401 out tokens · 113049 ms · 2026-08-01T21:34:34.633029+00:00 · methodology

0 comments
read the original abstract

Observations of the aromatic infrared emission band at 3.3 $\mu$m often reveal satellite emission features in the 3.4 - 3.6 $\mu$m range. While the 3.3 $\mu$m band is attributed to the CH stretching vibration of polycylic aromatic hydrocarbons (PAHs), the satellite bands - particularly its prominent 3.4 $\mu$m component - is assigned to aliphatic CH stretching vibrations in hydrogenated and methylated PAH-like species. Our aim is to derive state-of-the-art infrared emission spectra for aliphatic-containing pyrene derivatives and compare them with astronomical observations. This will help refine our understanding of the contribution of these species to the 3.4 $\mu$m emission band. Mid-infrared spectra (1.4-25 $\mu$m) of gas-phase dihydropyrene, tehtrahydropyrene, hexahydropyrene methylated pyrene, and pyrene were recorded at temperatures ranging from 373 to 673 K, depending on the species. The band profiles were analyzed using a multi-component fitting tool, and empirical anharmonicity laws were derived to quantify the evolution of the band positions and widths with temperature. The obtained spectral data was combined with the results of a Monte Carlo emission model to simulate the emission spectra following UV-photon absorption, up to the dissociation limit ($\lesssim$6 eV). The resulting synthetic spectra were compared with James Webb Space Telescope observations of the Orion Bar region (PDRs4All program). Based on these state-of-the-art simulated spectra, we propose 1,2,3,6,7,8-hexahydropyrene as the carrier of the red component of the 3.4 $\mu$m band observed at 3.403 $\mu$m. While 1-methylpyrene may also contribute to the underlying emission plateau, its lack of a strong infrared band complicates detection in observed spectra, unlike hexahydropyrene. All experimental spectra and their temperature-dependent analyses are available in the new cosmicPAH-IRDB database.

Figures

Figures reproduced from arXiv: 2607.16018 by Christine Joblin, Dominique Toublanc, Giacomo Mulas, Karine Demyk, Louan de Bentzmann.

Figure 1
Figure 1. Figure 1: Infrared spectra of pyrene, hydrogenated (2H-, 4H- and 6H-)pyrene and methylated pyrene in the gas phase at 473 K. Left: [PITH_FULL_IMAGE:figures/full_fig_p004_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Comparison of 6H-pyrene spectrum in the gas phase ( [PITH_FULL_IMAGE:figures/full_fig_p005_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Infrared spectra of 6H-pyrene and Me-pyrene at various temperatures in the CH stretching mode spectral region. The spectra [PITH_FULL_IMAGE:figures/full_fig_p007_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: Comparison of the spectra of 2H-pyrene, 4H-pyrene, 6H [PITH_FULL_IMAGE:figures/full_fig_p009_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: Emission spectrum of 6H-pyrene (left panel) and Me-pyrene (right panel), modelled for the absorption of photons of energy of 4, 5, 5.5, and 6 eV [PITH_FULL_IMAGE:figures/full_fig_p010_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: Comparison of the JWST observations of the Orion PDR (DF3; Van De Putte et al. 2025) with experimental and modelled [PITH_FULL_IMAGE:figures/full_fig_p010_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: Comparison of the simulated emission spectrum of 6H [PITH_FULL_IMAGE:figures/full_fig_p011_7.png] view at source ↗

discussion (0)

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Reference graph

Works this paper leans on

235 extracted references · 60 canonical work pages

  1. [1]

    , keywords =

    Widespread Detection of Aromatic and Aliphatic Emission in the Dual Quasar J0749+2255 at Cosmic Noon. , keywords =. doi:10.3847/2041-8213/ae7e86 , adsurl =

    work page doi:10.3847/2041-8213/ae7e86 2041

  2. [2]

    , keywords =

    Anharmonicity and the infrared emission spectrum of highly excited polycyclic aromatic hydrocarbons. , keywords =. doi:10.1051/0004-6361/201833731 , archivePrefix =. 1809.09868 , primaryClass =

    Pith/arXiv arXiv

  3. [3]

    , keywords =

    Carbonaceous nano-dust emission in proto-planetary discs: the aliphatic-aromatic components. , keywords =. doi:10.1051/0004-6361/201834016 , archivePrefix =. 1901.07332 , primaryClass =

    Pith/arXiv arXiv 1901

  4. [4]

    Far-ultraviolet-driven formation of simple hydrocarbon radicals and their relation with polycyclic aromatic hydrocarbons

    PDRs4All: XII. Far-ultraviolet-driven formation of simple hydrocarbon radicals and their relation with polycyclic aromatic hydrocarbons. , keywords =. doi:10.1051/0004-6361/202453350 , archivePrefix =. 2503.03353 , primaryClass =

    Pith/arXiv arXiv

  5. [5]

    Detections of interstellar aromatic nitriles 2-cyanopyrene and 4-cyanopyrene in. Nat. Astron. , author =. 2025 , pages =. doi:10.1038/s41550-024-02410-9 , number =

    doi:10.1038/s41550-024-02410-9 2025

  6. [6]

    Science , year = 2024, month = nov, volume =

    Detection of interstellar 1-cyanopyrene: A four-ring polycyclic aromatic hydrocarbon. Science , year = 2024, month = nov, volume =. doi:10.1126/science.adq6391 , adsurl =

    doi:10.1126/science.adq6391 2024

  7. [7]

    , keywords =

    Variations in the 3 Micron Spectrum across the Orion Bar: Polycyclic Aromatic Hydrocarbons and Related Molecules. , keywords =. doi:10.1086/303484 , adsurl =

    doi:10.1086/303484

  8. [8]

    , keywords =

    Astrochemical relevance of VUV ionization of large PAH cations. , keywords =. doi:10.1051/0004-6361/202038139 , archivePrefix =. 2005.02103 , primaryClass =

    Pith/arXiv arXiv 2005

  9. [9]

    , keywords =

    VUV Photo-processing of PAH Cations: Quantitative Study on the Ionization versus Fragmentation Processes. , keywords =. doi:10.3847/0004-637X/822/2/113 , archivePrefix =. 1602.05015 , primaryClass =

    Pith/arXiv arXiv

  10. [10]

    , keywords =

    A general model for the identification of specific PAHs in the far-IR. , keywords =. doi:10.1051/0004-6361:20054276 , archivePrefix =. astro-ph/0606264 , primaryClass =

    Pith/arXiv arXiv

  11. [11]

    Aliphatic and aromatic carbonaceous dust, ices, and gas-phase spectral line inventory

    JWST observations of photodissociation regions: I. Aliphatic and aromatic carbonaceous dust, ices, and gas-phase spectral line inventory. , keywords =. doi:10.1051/0004-6361/202554851 , archivePrefix =. 2506.20468 , primaryClass =

    Pith/arXiv arXiv

  12. [12]

    , keywords =

    A Sensitivity Analysis of the Modeling of Polycyclic Aromatic Hydrocarbon Emission in Galaxies. , keywords =. doi:10.3847/1538-4357/ad9918 , archivePrefix =. 2412.01875 , primaryClass =

    Pith/arXiv arXiv

  13. [13]

    , keywords =

    Investigation of the Ultraviolet, Visible, and Near-Infrared Absorption Spectra of Hydrogenated Polycyclic Aromatic Hydrocarbons and Their Cations. , keywords =. doi:10.1086/430631 , adsurl =

    work page doi:10.1086/430631

  14. [14]

    EAS Publications Series , year = 2009, editor =

    Interstellar polycylic aromatic hydrocarbons: from space to the laboratory. EAS Publications Series , year = 2009, editor =. doi:10.1051/eas/0935008 , adsurl =

    arXiv 2009

  15. [15]

    Western , keywords =

    Colin M. Western , keywords =. PGOPHER: A program for simulating rotational, vibrational and electronic spectra , journal =. 2017 , note =. doi:https://doi.org/10.1016/j.jqsrt.2016.04.010 , url =

    doi:10.1016/j.jqsrt.2016.04.010 2017

  16. [16]

    and Boersma, C

    Ricca, A. and Boersma, C. and Maragkoudakis, A. and Roser, J. E. and Shannon, Matthew J. and Allamandola, L. J. and Bauschlicher, Charles W. , title =. The Astrophysical Journal Supplement Series , abstract =. 2025 , month =. doi:10.3847/1538-4365/ae1c38 , url =

    doi:10.3847/1538-4365/ae1c38 2025

  17. [17]

    and Esposito, Vincent J

    Stockett, Mark H. and Esposito, Vincent J. and Ashworth, Eleanor K. and Jacovella, Ugo and Bull, James N. , title =. ACS Earth and Space Chemistry , volume =. 2025 , doi =

    2025

  18. [18]

    and Candian, Alessandra and Lee, Timothy J

    Mackie, Cameron J. and Candian, Alessandra and Lee, Timothy J. and Tielens, Alexander G. G. M. , urldate =. Anharmonicity and the. 2022 , langid =. doi:10.1021/acs.jpca.2c01849 , abstract =

    work page doi:10.1021/acs.jpca.2c01849 2022

  19. [19]

    and Candian, Alessandra and Lee, Timothy J

    Mackie, Cameron J. and Candian, Alessandra and Lee, Timothy J. and Tielens, Alexander G. G. M. , year =. Modeling the infrared cascade spectra of small. doi:10.1007/s00214-021-02807-z , abstract =

    work page doi:10.1007/s00214-021-02807-z

  20. [20]

    , title =

    West, Brandi and Lowe, Bethany and Mayer, Paul M. , title =. The Journal of Physical Chemistry A , volume =. 2018 , doi =

    2018

  21. [21]

    , keywords =

    Competitive Dehydrogenation and Backbone Fragmentation of Superhydrogenated PAHs: A Laboratory Study. , keywords =. doi:10.3847/1538-4357/abf354 , adsurl =

    work page doi:10.3847/1538-4357/abf354

  22. [22]

    , keywords =

    The PAH 3.4 micron feature as a tracer of shielding in the Orion Bar and NGC 6240. , keywords =. doi:10.1093/mnras/staf2047 , archivePrefix =. 2511.13395 , primaryClass =

    arXiv

  23. [23]

    Rapid Communications in Mass Spectrometry , volume =

    Joblin, Christine and Masselon, Christophe and Boissel, Pierre and de Parseval, Patrick and Martinovic, Suzana and Muller, Jean-François , title =. Rapid Communications in Mass Spectrometry , volume =. doi:https://doi.org/10.1002/(SICI)1097-0231(199709)11:14<1619::AID-RCM995>3.0.CO;2-P , url =. https://analyticalsciencejournals.onlinelibrary.wiley.com/doi...

    work page doi:10.1002/(sici)1097-0231(199709)11:14

  24. [24]

    , keywords =

    The Aromatic Infrared Bands as seen by ISO-SWS: Probing the PAH model. , keywords =. doi:10.1051/0004-6361:20010515 , archivePrefix =. astro-ph/0104144 , primaryClass =

    Pith/arXiv arXiv

  25. [25]

    Physical Chemistry Chemical Physics (Incorporating Faraday Transactions) , year = 2011, month = jan, volume =

    Molecular dynamics simulations on [FePAH]+ -complexes of astrophysical interest: anharmonic infrared spectroscopy. Physical Chemistry Chemical Physics (Incorporating Faraday Transactions) , year = 2011, month = jan, volume =. doi:10.1039/C0CP00990C , adsurl =

    work page doi:10.1039/c0cp00990c 2011

  26. [26]

    and Basire, M

    Calvo, F. and Basire, M. and Parneix, P. , title =. The Journal of Physical Chemistry A , volume =. 2011 , doi =

    2011

  27. [27]

    , keywords =

    Superhydrogenated Polycyclic Aromatic Hydrocarbon Molecules: Vibrational Spectra in the Infrared. , keywords =. doi:10.3847/1538-4365/ab67b6 , archivePrefix =. 2001.00717 , primaryClass =

    Pith/arXiv arXiv 2001

  28. [28]

    , keywords =

    The Carriers of the Interstellar Unidentified Infrared Emission Features: Constraints from the Interstellar C-H Stretching Features at 3.2-3.5 m. , keywords =. doi:10.1088/0004-637X/776/2/110 , archivePrefix =. 1309.1993 , primaryClass =

    Pith/arXiv arXiv 1993

  29. [29]

    Molecular Physics , year = 2002, month = jan, volume =

    Calculations of the far-infrared emission of C 24 H 12 under interstellar conditions. Molecular Physics , year = 2002, month = jan, volume =. doi:10.1080/00268970210161485 , adsurl =

    work page doi:10.1080/00268970210161485 2002

  30. [30]

    PDRs4All. VII. The 3.3 m aromatic infrared band as a tracer of physical properties of the interstellar medium in galaxies. , keywords =. doi:10.1051/0004-6361/202348974 , archivePrefix =. 2402.16535 , primaryClass =

    Pith/arXiv arXiv

  31. [31]

    Spectrochimica Acta Part A: Molecular Spectroscopy , year = 2001, month = mar, volume =

    Hydrogenation of polycyclic aromatic hydrocarbons as a factor affecting the cosmic 6.2 micron emission band. Spectrochimica Acta Part A: Molecular Spectroscopy , year = 2001, month = mar, volume =. doi:10.1016/S1386-1425(00)00440-6 , adsurl =

    work page doi:10.1016/s1386-1425(00)00440-6 2001

  32. [32]

    , keywords =

    DFT Study on Interstellar PAH Molecules with Aliphatic Side Groups. , keywords =. doi:10.3847/1538-4357/ab733a , archivePrefix =. 2003.10691 , primaryClass =

    Pith/arXiv arXiv 2003

  33. [33]

    , keywords =

    Direct Spectroscopic Evidence for Ionized Polycyclic Aromatic Hydrocarbons in the Interstellar Medium. , keywords =. doi:10.1086/311906 , archivePrefix =. astro-ph/9902077 , primaryClass =

    Pith/arXiv arXiv

  34. [34]

    , keywords =

    Variations of the 8.6 and 11.3 MU M Emission Bands within NGC 1333: Evidence for PAH Cations. , keywords =. doi:10.1086/309986 , adsurl =

    doi:10.1086/309986

  35. [35]

    , keywords =

    Interpreting the Subtle Spectral Variations of the 11.2 and 12.7 m Polycyclic Aromatic Hydrocarbon Bands. , keywords =. doi:10.3847/0004-637X/824/2/111 , archivePrefix =. 1604.08589 , primaryClass =

    Pith/arXiv arXiv

  36. [36]

    , keywords =

    Evaporating very small grains as tracers of the UV radiation field in photo-dissociation regions. , keywords =. doi:10.1051/0004-6361/201015915 , archivePrefix =. 1204.4669 , primaryClass =

    Pith/arXiv arXiv

  37. [37]

    Hydrogenation and charge states

    Evolution of polycyclic aromatic hydrocarbons in photodissociation regions. Hydrogenation and charge states. , keywords =. doi:10.1051/0004-6361/201220757 , archivePrefix =. 1301.6507 , primaryClass =

    Pith/arXiv arXiv

  38. [38]

    , keywords =

    Analysis of the emission of very small dust particles from Spitzer spectro-imagery data using blind signal separation methods. , keywords =. doi:10.1051/0004-6361:20066282 , archivePrefix =. astro-ph/0703072 , primaryClass =

    Pith/arXiv arXiv

  39. [39]

    Reviews of Modern Physics , keywords =

    Photodissociation regions in the interstellar medium of galaxies. Reviews of Modern Physics , keywords =. doi:10.1103/RevModPhys.71.173 , adsurl =

    doi:10.1103/revmodphys.71.173

  40. [40]

    , keywords =

    The rich 6 to 9 vec mu m spectrum of interstellar PAHs. , keywords =. doi:10.1051/0004-6361:20020773 , archivePrefix =. astro-ph/0205400 , primaryClass =

    Pith/arXiv arXiv

  41. [41]

    Nature Astronomy , keywords =

    Spitzer's perspective of polycyclic aromatic hydrocarbons in galaxies. Nature Astronomy , keywords =. doi:10.1038/s41550-020-1051-1 , archivePrefix =. 2003.10489 , primaryClass =

    Pith/arXiv arXiv 2003

  42. [42]

    , keywords =

    The PAH Emission Characteristics of the Reflection Nebula NGC 2023. , keywords =. doi:10.3847/1538-4357/836/2/198 , archivePrefix =. 1701.06585 , primaryClass =

    Pith/arXiv arXiv 2023

  43. [43]

    , keywords =

    Orion Bar as a window to the evolution of PAHs. , keywords =. doi:10.1093/mnras/stab3061 , archivePrefix =. 2111.05583 , primaryClass =

    Pith/arXiv arXiv

  44. [44]

    , keywords =

    The Detection of 6.9 m Emission Features in the Infrared Spectra of IRAS 04296+3429, IRAS 05341+0852, and IRAS 22272+5435: Evidence for the Presence of H _ n -PAHs in Post-AGB Stars. , keywords =. doi:10.3847/1538-4357/aa960d , adsurl =

    doi:10.3847/1538-4357/aa960d

  45. [45]

    , keywords =

    The profiles of the aromatic infrared bands explained with molecular carriers. , keywords =. doi:10.1051/0004-6361:20020416 , adsurl =

    doi:10.1051/0004-6361:20020416

  46. [46]

    doi:10.1086/177217 , Journal =

    doi:10.1086/177217

  47. [47]

    , keywords =

    Interstellar Polycyclic Aromatic Hydrocarbons: The Infrared Emission Bands, the Excitation/Emission Mechanism, and the Astrophysical Implications. , keywords =. doi:10.1086/191396 , adsurl =

    doi:10.1086/191396

  48. [48]

    doi:10.1051/0004-6361/201014657 , Eprint =

    , Keywords =. doi:10.1051/0004-6361/201014657 , Eprint =

    doi:10.1051/0004-6361/201014657

  49. [49]

    doi:10.1086/374263 , Eprint =

    , Keywords =. doi:10.1086/374263 , Eprint =

    doi:10.1086/374263

  50. [50]

    , keywords =

    Anharmonicity and the Interstellar Polycyclic Aromatic Hydrocarbon Infrared Emission Spectrum. , keywords =. doi:10.1086/184861 , adsurl =

    doi:10.1086/184861

  51. [51]

    Journal of Chemical Theory and Computation , volume =

    Barone, Vincenzo and Cimino, Paola and Stendardo, Emiliano , title =. Journal of Chemical Theory and Computation , volume =. 2008 , doi =

    2008

  52. [52]

    , keywords =

    The NASA Ames PAH IR Spectroscopic Database: Computational Version 3.00 with Updated Content and the Introduction of Multiple Scaling Factors. , keywords =. doi:10.3847/1538-4365/aaa019 , adsurl =

    doi:10.3847/1538-4365/aaa019

  53. [53]

    doi:10.1086/516745 , Journal =

    doi:10.1086/516745

  54. [54]

    , keywords =

    Hydrogenated Polycyclic Aromatic Hydrocarbons and the 2940 and 2850 Wavenumber (3.40 and 3.51 micron) Infrared Emission Features. , keywords =. doi:10.1086/310376 , adsurl =

    doi:10.1086/310376

  55. [55]

    Becke , Doi =

    Axel D. Becke , Doi =. Density-functional thermochemistry. III. The role of exact exchange , Volume =. J. Chem. Phys. , Pages =

  56. [56]

    Bish, D. L. and Howard, S. A. , Doi =. Journal of Applied Crystallography , Month =. 1988 , Bdsk-Url-1 =

    1988

  57. [57]

    , year = 2012, month = sep, volume = 93, pages =

    Circumstellar and interstellar material in the CO3 chondrite ALHA77307: An isotopic and elemental investigation. , year = 2012, month = sep, volume = 93, pages =. doi:10.1016/j.gca.2012.06.027 , adsurl =

    work page doi:10.1016/j.gca.2012.06.027 2012

  58. [58]

    doi:10.1086/426964 , Eprint =

    , Keywords =. doi:10.1086/426964 , Eprint =

    doi:10.1086/426964

  59. [59]

    doi:10.1051/0004-6361:20065139 , Eprint =

    , Keywords =. doi:10.1051/0004-6361:20065139 , Eprint =

    doi:10.1051/0004-6361:20065139

  60. [61]

    doi:10.1051/0004-6361:200809673 , Eprint =

    , Keywords =. doi:10.1051/0004-6361:200809673 , Eprint =

    work page doi:10.1051/0004-6361:200809673

  61. [62]

    Bohren, Donald R

    Absorption and Scattering of Light by Small Particles, by Craig F. Bohren, Donald R. Huffman, pp. 544. ISBN 0-471-29340-7. Wiley-VCH , March 1998. , Editor =

    1998

  62. [63]

    doi:10.1051/0004-6361/201014986 , Eprint =

    , Keywords =. doi:10.1051/0004-6361/201014986 , Eprint =

    doi:10.1051/0004-6361/201014986

  63. [64]

    doi:10.1086/432966 , Journal =

    doi:10.1086/432966

  64. [65]

    Science , year = 1994, month = aug, volume = 265, pages =

    Chemically Anomalous, Preaccretionally Irradiated Grains in Interplanetary Dust From Comets. Science , year = 1994, month = aug, volume = 265, pages =. doi:10.1126/science.265.5174.925 , adsurl =

    doi:10.1126/science.265.5174.925 1994

  65. [66]

    American Institute of Physics Conference Series , Doi =

  66. [67]

    to be submitted to , Month = -, Title =

  67. [68]

    doi:10.1086/378038 , Journal =

    doi:10.1086/378038

  68. [69]

    doi:10.1051/0004-6361:20010559 , Journal =

    doi:10.1051/0004-6361:20010559

  69. [70]

    Journal of Molecular Spectroscopy , keywords =

    Anharmonic infrared spectra of thermally excited pyrene (C _ 16 H _ 10 ): A combined view of DFT-based GVPT2 with AnharmonicCaOs, and approximate DFT molecular dynamics with demonNano. Journal of Molecular Spectroscopy , keywords =. doi:10.1016/j.jms.2021.111466 , archivePrefix =. 2102.06582 , primaryClass =

    arXiv 2021

  70. [71]

    Journal of Physical Chemistry A , keywords =

    Experimental Approach to the Study of Anharmonicity in the Infrared Spectrum of Pyrene from 14 to 723 K. Journal of Physical Chemistry A , keywords =. doi:10.1021/acs.jpca.8b11016 , archivePrefix =. 1904.02899 , primaryClass =

    Pith/arXiv arXiv 1904

  71. [72]

    doi:10.1086/310697 , Journal =

    doi:10.1086/310697

  72. [73]

    , keywords =

    The Composition and Distribution of Dust along the Line of Sight toward the Galactic Center. , keywords =. doi:10.1086/309047 , archivePrefix =. astro-ph/0002421 , primaryClass =

    Pith/arXiv arXiv

  73. [74]

    doi:10.1051/0004-6361:20020791 , Journal =

    doi:10.1051/0004-6361:20020791

  74. [75]

    PDRs4All. IV. An embarrassment of riches: Aromatic infrared bands in the Orion Bar. , keywords =. doi:10.1051/0004-6361/202346662 , archivePrefix =. 2308.16733 , primaryClass =

    Pith/arXiv arXiv

  75. [76]

    Chrissanthopoulos and N

    A. Chrissanthopoulos and N. Bouropoulos and S.N. Yannopoulos , Doi =. Vibrational spectroscopic and computational studies of sol-gel derived CaO-MgO-SiO2 binary and ternary bioactive glasses , Url =. Vibrational Spectroscopy , Keywords =. 2008 , Bdsk-Url-1 =

    2008

  76. [77]

    doi:10.1051/0004-6361/201015292 , Eprint =

    , Keywords =. doi:10.1051/0004-6361/201015292 , Eprint =

    doi:10.1051/0004-6361/201015292

  77. [78]

    , archivePrefix = "arXiv", eprint =

    Low-temperature FIR and submillimetre mass absorption coefficient of interstellar silicate dust analogues. , archivePrefix = "arXiv", eprint =. doi:10.1051/0004-6361/201116945 , adsurl =

    doi:10.1051/0004-6361/201116945

  78. [79]

    Photoproduction of the 3.4, 6.85 and 7.25 m features

    Diffuse interstellar medium organic polymers. Photoproduction of the 3.4, 6.85 and 7.25 m features. , keywords =. doi:10.1051/0004-6361:200400032 , adsurl =

    doi:10.1051/0004-6361:200400032

  79. [80]

    , keywords =

    Organic matter in Seyfert 2 nuclei: Comparison with our Galactic center lines of sight. , keywords =. doi:10.1051/0004-6361:20047067 , archivePrefix =. astro-ph/0405327 , primaryClass =

    Pith/arXiv arXiv

  80. [81]

    PoS(LDCU2013)044 , year = 2013, eid =

    FIR and Submm Optical Properties of Astrophysically Relevant Minerals. PoS(LDCU2013)044 , year = 2013, eid =

    2013

Showing first 80 references.