Electronic spectra of cationic PAH and PAH clusters

Friha, Hela; Féraud, Géraldine; Pino, T.; Parneix, P.; Dhaouadi, Zoubeida; Bréchignac, Ph.

doi:10.1051/eas/1258063

Cited by 3 publications

(3 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…From the experimental side, mostly driven by the identification of astrophysical nanograins, the spectroscopic properties of PAH clusters have been reported in the IR-FIR as well as in the UV range. ,,− Most of the experiments devoted to the characterization of PAH clusters structural properties reported stacked structures for small clusters, sometime suggesting a parallel displaced (PD) pattern. ,, For instance, Wang et al produced nanoclusters of hydrocarbon molecules by annealing coronene films deposited on Pt(111) and observed stacking patterns with scanning tunneling microscopy. Ion mobility spectra suggest a formation as a single stack perturbed by side molecules when the number of units increases .…”

Section: Introductionmentioning

confidence: 99%

Structures and Energetics of Neutral and Cationic Pyrene Clusters

2019

View full text Add to dashboard Cite

The low energy structures of neutral and cationic pyrene clusters containing up to seven molecules are searched through a global exploration scheme combining parallel tempering Monte Carlo algorithm and local quenches. The potential energies are computed at the density functional based tight binding level for neutrals and configuration interaction density functional based tight binding for cations in order to treat properly the charge resonance. New simplified versions of these schemes are also presented and used during the global exploration. Neutral clusters are shown to be made of compact assemblies of sub-blocs containing up to three units whereas cations present a charged dimer or trimer core surrounded by neutral units. The structural features of the clusters are analyzed and correlated for the cation with the charge distribution. The stability of clusters is also discussed in terms of cohesive and evaporation energies. Adiabatic and vertical ionization potentials are also discussed.

show abstract

Section: Introductionmentioning

confidence: 99%

Structures and Energetics of Neutral and Cationic Pyrene Clusters

2019

View full text Add to dashboard Cite

show abstract

“…Charged PAH clusters were also proposed as the carriers of another observational feature, the Extended Red Emission [26]. These observational insights have motivated experimental and theoretical studies on the spectral properties of PAH clusters in the IR or UV-Vis domain [27][28][29][30][31]. The evolution of the ionization potential of PAH clusters with size was also studied [32].…”

Section: Introductionmentioning

confidence: 99%

Thermal evaporation of pyrene clusters

Zamith

L'Hermite

et al. 2019

The Journal of Chemical Physics

View full text Add to dashboard Cite

This work presents a study of the thermal evaporation and stability of pyrene (C 16 H 10)n clusters. Thermal evaporation rates of positively charged mass-selected clusters are measured for sizes in the range n=3-40 pyrene units. The experimental setup consists of a gas aggregation source, a thermalization chamber and a time of flight mass spectrometer. A microcanonical Phase Space Theory (PST) simulation is used to determine the dissociation energies of pyrene clusters by fitting the experimental breakdown curves. Calculations using the Density Functional based Tight Binding combined with Configuration Interaction (CI-DFTB) model and a hierarchical optimization scheme are also performed in the range n=2-7 to determine the harmonic frequencies and a theoretical estimation of the dissociation energies. The frequencies are used in the calculations of the density of states needed in the PST simulations, assuming an extrapolation scheme for clusters larger than 7 units. Using the PST model with a minimal set of adjustable parameters, we obtain good fits of the experimental breakdown curves over the full studied size range. The approximations inherent to the PST simulation and the influence of the used parameters are carefully estimated. The derived dissociation energies show significant variations over the studied size range. Compared to neutral clusters, significantly higher values of the dissociation energies are obtained for the smaller sizes and attributed to charge resonance in line with CI-DFTB calculations.

show abstract

“…From the experimental side, many studies focused on the investigation of structural properties of these clusters at the most stable geometrical configurations [5,7,[16][17][18][19]. Their energetic properties such as ionisation potentials have been recorded [20] as well as their spectral properties [21][22][23][24]. The stability of PAH clusters has also been investigated from experiments following the evaporation of these clusters after absorption of a photon or a collision process [25][26][27][28][29][30][31].…”

Section: Introductionmentioning

confidence: 99%

Dynamical simulation of collision-induced dissociation of pyrene dimer cation

2021

View full text Add to dashboard Cite

We report a theoretical investigation of the collision induced dissociation of pyrene dimer cation, as recently investigated in the experimental work by Zamith et al. (J. Chem. Phys. 153, 054311 (2020)). Molecular dynamics simulations using potential energies and forces computed at the self-consistent charge density functional based tight binding level were conducted for different collision energies between 2.5 and 30 eV. It appears that most of the dissociation occurs on a short timescale (less than 3 ps). The dynamical simulations allow to visualise the dissociation processes. At low collision energies, the dissociation cross section increases with collision energies whereas it remains almost constant for collision energies greater than 10-15 eV. The analysis of the kinetic energy partition is used to get insights into the collision/dissociation processes at the atomic scale. The simulated time of flight mass spectra of parent and dissociation products are obtained from the combination of molecular dynamics simulations and phase space theory to address the short and long timescales dissociation, respectively. The agreement between the simulated and measured mass spectra suggests that the main processes are captured by this approach.

show abstract

Electronic spectra of cationic PAH and PAH clusters

Cited by 3 publications

References 13 publications

Structures and Energetics of Neutral and Cationic Pyrene Clusters

Structures and Energetics of Neutral and Cationic Pyrene Clusters

Thermal evaporation of pyrene clusters

Dynamical simulation of collision-induced dissociation of pyrene dimer cation

Contact Info

Product

Resources

About