Direct measurement of recurrent fluorescence emission from naphthalene ions

Saito, Manabu; Kubota, H.; Yamasa, K.; Suzuki, Kenta; Majima, T.; Tsuchida, H.

doi:10.1103/physreva.102.012820

Cited by 28 publications

(24 citation statements)

References 22 publications

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“…This happens after a given cooling time (see Sect. 2.3), which depends on the efficiency of the radiative cooling involving the emission of IR photons and eventually visible photons by the so-called recurrent fluorescence mechanism (Léger et al 1988;Martin et al 2015;Saito et al 2020). The competition between fragmentation and radiative cooling, which governs the stability upon photodissociation, can be indirectly studied from the comparison of the values of fragmentation rates with those of photoabsorption rates.…”

Section: Molecular Parameters Involved In Vuv Photoprocessingmentioning

confidence: 99%

Photodissociation of aliphatic PAH derivatives under relevant astrophysical conditions

Marciniak

Joblin

Mulas

et al. 2021

A&A

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Context. The interaction of polycyclic aromatic hydrocarbons (PAHs) with vacuum ultraviolet (VUV) photons triggers the emission of the well-known aromatic infrared bands (AIBs), but other mechanisms, such as fragmentation, can be involved in this interaction. Fragmentation leads to selection effects that favor specific sizes and structures. Aims. Our aim is to investigate the impact of aliphatic bonds on the VUV photostability of PAH cations in a cryogenic and collisionless environment with conditions applicable for photodissociation regions (PDRs). Methods. The studied species are derived from pyrene (C16H10) and coronene (C24H12) and contain aliphatic bonds either in the form of methyl or ethyl sidegroups or of superhydrogenation. Their cations are produced by laser desorption ionization and isolated in the cryogenic ion cell of the PIRENEA setup, where they are submitted to VUV photons of 10.5 eV energy over long timescales (~1000 s). The parent and fragment ions are mass-analyzed and their relative intensities are recorded as a function of the irradiation time. The fragmentation cascades are analyzed with a simple kinetics model from which we identify fragmentation pathways and derive fragmentation rates and branching ratios for both the parents and their main fragments. Results. Aliphatic PAH derivatives are found to have a higher fragmentation rate and a higher carbon to hydrogen loss compared to regular PAHs. On the other hand, the fragmentation of PAHs with alkylated sidegroups forms species with peripheral pentagonal cycles, which can be as stable as, or even more stable than, the bare PAH cations. This stability is quantified for the main ions involved in the fragmentation cascades by the comparison of the fragmentation rates with the photoabsorption rates derived from theoretical photoabsorption cross sections. The most stable species for which there is an effective competition of fragmentation with isomerization and radiative cooling are identified, providing clues on the structures favored in PDRs. Conclusions. This work supports a scenario in which the evaporation of nanograins with a mixed aliphatic and aromatic composition followed by VUV photoprocessing results in both the production of the carriers of the 3.4 μm AIB by methyl sidegroups and in an abundant source of small hydrocarbons at the border of PDRs. An additional side effect is the efficient formation of stable PAHs that contain some peripheral pentagonal rings. Our experiments also support the role of isomerization processes in PAH photofragmentation, including the H-migration process, which could lead to an additional contribution to the 3.4 μm AIB.

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Section: Molecular Parameters Involved In Vuv Photoprocessingmentioning

confidence: 99%

Photodissociation of aliphatic PAH derivatives under relevant astrophysical conditions

Marciniak

Joblin

Mulas

et al. 2021

A&A

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“…Very recently, recurrent fluorescence photons emitted by hot naphthalene cations were directly observed in an electrostatic ion beam trap. 15 Laser probing techniques have been used to investigate the time evolution of the internal energy distribution of highly excited PAHs. 16,17 Action spectroscopy techniques have provided information on slower, infrared cooling rates 18,19 as well as photostabilities.…”

Section: Introductionmentioning

confidence: 99%

Unimolecular fragmentation and radiative cooling of isolated PAH ions: A quantitative study

Stockett

Bull

Buntine

et al. 2020

The Journal of Chemical Physics

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Time-resolved spontaneous and laser-induced unimolecular fragmentation of perylene cations (C 20 H 12 + ) has been measured on timescales up to 2 s in a cryogenic electrostatic ion beam storage ring. We elaborate a quantitative model, which includes fragmentation in competition with radiative cooling via both vibrational and electronic (recurrent fluorescence) de-excitation. Excellent agreement with experimental results is found when sequential fragmentation of daughter ions co-stored with the parent perylene ions is included in the model. Based on the comparison of the model to experiment, we constrain the oscillator strength of the D 1 → D 0 emissive electronic transition in perylene (f RF = 0.055 ± 0.011), as well as the absolute absorption cross section of the D5 ← D 0 excitation transition (σ abs > 670 Mb). The former transition is responsible for the laser-induced and recurrent fluorescence of perylene, and the latter is the most prominent in the absorption spectrum. The vibrational cooling rate is found to be consistent with the simple harmonic cascade approximation. Quantitative experimental benchmarks of unimolecular processes in polycyclic aromatic hydrocarbon ions like perylene are important for refining astrochemical models.

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“…In all these cases, we have shown that a fast radiative cooling process referred to as recurrent fluorescence (RF), was responsible for the fast reduction of the internal energy of PAH cations produced in the plasma of an electron cyclotron resonance (ECR) ion source (28)(29)(30)(31). Recently, the RF photon emission has been directly detected for naphthalene cations using an ion beam trap (32).…”

Section: Introductionmentioning

confidence: 99%

Experimental and theoretical study of photo-dissociation spectroscopy of pyrene dimer radical cations stored in a compact electrostatic ion storage ring

Bernard

Al‐Mogeeth

Martin

et al. 2021

Phys. Chem. Chem. Phys.

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Direct measurement of recurrent fluorescence emission from naphthalene ions

Cited by 28 publications

References 22 publications

Photodissociation of aliphatic PAH derivatives under relevant astrophysical conditions

Photodissociation of aliphatic PAH derivatives under relevant astrophysical conditions

Unimolecular fragmentation and radiative cooling of isolated PAH ions: A quantitative study

Experimental and theoretical study of photo-dissociation spectroscopy of pyrene dimer radical cations stored in a compact electrostatic ion storage ring

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