Photodissociation kinetics of clusters

Abstract

The photodissociation dynamics of size-selected C + n clusters with 19 n 29 is analysed using visible and UV irradiation. Both the number of absorbed photons leading to dissociation, and the time decay of the associated internal energy state are determined. The measured dissociation time constants indicate an evaporative behaviour, where energy redistribution over the modes of vibration occurs before dissociation.The RRKM theory is therefore used and shown to lead to low dissociation energies. At the low levels of internal energy reached in our photodissociation experiments, a more appropriate model is proposed, which accounts for a restricted redistribution of energy inside the cluster. This model leads to dissociation energies ranging from 4.05 to 3.3 eV.One-photon dissociation is also observed with photon energies close to 4.5 eV. On the one hand, this suggests a dissociative process for this photo-excitation wavelength. On the other hand, it allows to get upper limits for the dissociation energies.

Fragmentation of small carbon clusters, a review

“…We will present some of their results in Section 5. Later on, the same kind of apparatus was used by Bouyer et al [6] for studying the kinetics of dissociation of larger C þ n (n = 19-29) species. Metastable dissociation (ls) of C þ n clusters (n = 5-60) was studied by Radi et al [7] also quite a time ago.…”

“…Fig. 6. Comparison between C + /C þþ nÀ1 branching ratio (black circle), C þ 2 /C þþ nÀ2 branching ratio (open triangle) and C þ 3 /C þþ nÀ3 branching ratio (black square) in the fragmentation of C þþþ n clusters as a function of n. Branching ratios are normalised to the total two-fragments dissociation.…”