Single and double photoionization processes in naphthalene between 8 and 35 eV

Ruehl, E.; Price, S. D.; Leach, Sydney

doi:10.1021/j100354a011

Cited by 62 publications

(37 citation statements)

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“…Their hard photons could, according to laboratory experiments (Ruhl et al 1989;Leach et al 1989a,b;Jochims et al 1994) and theory (Omont 1986;Tielens 2005;Rapacioli et al 2006;Micelotta et al 2010a,b), destroy PAHs. We discuss below their impact on the PAH abundance in the disks of T Tauri stars.…”

Section: Introductionmentioning

confidence: 98%

The destruction and survival of polycyclic aromatic hydrocarbons in the disks of T Tauri stars

Siebenmorgen

Krügel

2010

A&A

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In Spitzer observations of Tauri stars and their disks, features of polycyclic aromatic hydrocarbons (PAHs) are detected in less than 10% of the objects, although the stellar photosphere is sufficiently hot to excite PAHs. To explain the deficiency, we discuss PAH destruction by photons, assuming that the star has beside its photospheric emission also a far ultraviolet (FUV), an extreme ultraviolet (EUV) and an X-ray component with a fractional luminosity of 1%, 0.1% and 0.025%, respectively. We consider as a PAH destruction process unimolecular dissociation and present a simplified scheme to estimate the location from the star at which the molecules become photo-stable. We find that soft photons with energies below ∼20 eV dissociate PAHs only up to short distances from the star (r < 1 AU); whereas dissociation by hard photons (EUV and X-ray) is so efficient that it would destroy all PAHs (from regions in the disk where they could be excited). As a possible path for PAH-survival we suggest turbulent motions in the disk. They can replenish or remove PAHs from the reach of hard photons. For standard disk models, where the surface density changes like r −1 and the mid plane temperature like r −0.5 , the critical vertical velocity for PAH survival is proportional to r −3/4 and equals ∼5 m/s at 10 AU, which is in the range of expected velocities in the surface layer. The uncertainty in the parameters is large enough to explain both detection and non-detection of PAHs. Our approximate treatment also takes into account the presence of gas which is ionized at the top of the disk and neutral at lower levels.

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Section: Introductionmentioning

confidence: 98%

The destruction and survival of polycyclic aromatic hydrocarbons in the disks of T Tauri stars

Siebenmorgen

Krügel

2010

A&A

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“…The interaction energy for the formation of larger sized fragments according to reactions iv -viii needs to be well above 22 eV as discussed by Ruhl et al [18]. The plasmon excitation is expected to peak at about 17 eV [26].…”

Section: Resultsmentioning

confidence: 92%

“…If the decay constants are in the range of 10 5 $ 10 6 , then the thermal velocity dispersion does not affect the collection efficiency if it becomes possible to probe the system within sufficient time. Even though such a unique system has limited applicability, it has helped in our present investigation to study the evaporative loss from a PAH molecule due to electron impact and the decay rate for acetylene and diacetylene loss in naphthalene has been shown to have decay constant in the range of 10 5 $ 10 6 sec À1 at 8-9 eV internal energy [12,18]. So, the decay time of acetylene and diacetylene is of the order of 1-10 μs.…”

Section: Introductionmentioning

confidence: 97%

“…It is also seen that acetylene (C 2 H 2 ) loss comes as a by-product of such plasmon excitation with a very specific range of decay constants. We use naphthalene as a model since it exhibits many general spectroscopic and structural properties of larger PAHs [18]. An attempt is made to investigate the interaction of high energy electron beam with PAHs and assess the time dependence of C 2 H 2 evaporation in comparison with the other channels using a Time-of-Flight (ToF) mass spectrometer.…”

Section: Introductionmentioning

confidence: 99%

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Large Molecule Fragmentation Dynamics Using Delayed Extraction Time-of-Flight Mass Spectroscopy

Najeeb¹

2019

Mass Spectrometry - Future Perceptions and Applications

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A time-of-flight mass spectrometer with a pulsed electron beam, delayed and pulsed extraction of the recoil ion is reported. This new technique is named as Delayed Extraction Time of Flight Mass Spectrometer (DEToF). The effectiveness of this technique is highlighted by studying the statistical decay of mono-cations over microsecond timescales from large molecules. Various details of the design and operation are performed in the context of electron impact ionization and fragmentation of few PAHs, naphthalene (C 10 H 8), quinoline (C 9 H 8 N) and it isomer Isoquinoline (C 9 H 8 N) and are used as a test bench mark for large molecules fragmentation dynamics using DEToF. In this chapter we discuss the fragmentation dynamics of Naphthalene molecule and time evolution of various fragmentation channels of these PAH, explored using a rapid but delayed extraction of recoil ions. The temporal behavior of acetylene (C 2 H 2), HCN, diacetylene (C 4 H 2) and C 2 H 2 +HCN loss are observed and compared with the associated Arrhenius decay constant, internal energy and plasmon excitation energy.

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“…2 In particular, gas-phase PAH interactions with energetic photons have been the subject of intense study because of the direct relevance of such processes in astrophysical environments 3 and because of the opportunities of PAH photoionization as a tool for analytical chemistry. 4 In a series of pioneering experiments, using synchrotron radiation, Leach and coworkers have investigated vacuum ultraviolet (VUV) photoionization of a variety of gas-phase neutral PAHs by means of photoelectron-photoion coincidence spectroscopy 5,6 or by photoionization mass spectrometry. 7 Upon moderate excitation, PAH cations dissociate predominantly by neutral H atom, or H 2 loss, or by acetylene loss, with appearance photon energies increasing with PAH size.…”

Section: Introductionmentioning

confidence: 99%

Near edge X-ray absorption mass spectrometry on coronene

Reitsma

Boschman

Deuzeman

et al. 2015

The Journal of Chemical Physics

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We have investigated the photoionization and photodissociation of free coronene cations C24H12 (+) upon soft X-ray photoabsorption in the carbon K-edge region by means of a time-of-flight mass spectrometry approach. Core excitation into an unoccupied molecular orbital (below threshold) and core ionization into the continuum both leave a C 1s vacancy, that is subsequently filled in an Auger-type process. The resulting coronene dications and trications are internally excited and cool down predominantly by means of hydrogen emission. Density functional theory was employed to determine the dissociation energies for subsequent neutral hydrogen loss. A statistical cascade model incorporating these dissociation energies agrees well with the experimentally observed dehydrogenation. For double ionization, i.e., formation of intermediate C24H12 (3+⋆)trications, the experimental data hint at loss of H(+) ions. This asymmetric fission channel is associated with hot intermediates, whereas colder intermediates predominantly decay via neutral H loss.

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Single and double photoionization processes in naphthalene between 8 and 35 eV

Cited by 62 publications

References 0 publications

The destruction and survival of polycyclic aromatic hydrocarbons in the disks of T Tauri stars

The destruction and survival of polycyclic aromatic hydrocarbons in the disks of T Tauri stars

Large Molecule Fragmentation Dynamics Using Delayed Extraction Time-of-Flight Mass Spectroscopy

Near edge X-ray absorption mass spectrometry on coronene

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