Evaporation of covalent clusters: Unimolecular decay of energized size-selected carbon cluster ions (C+n, 5≤n≤100)

Abstract

Controlling the internal energy content of sizeselected cluster ions: An experimental comparison of the metastable decay rate and photofragmentation methods of quantifying the internal excitation of (H2O)− n J. Chem. Phys. 95, 7998 (1991); 10.1063/1.461330 Reply to the Comment on: Evaporation of covalent clusters: Unimolecular decay of energized size selected carbon clusters J. Chem. Phys. 94, 6934 (1991); 10.1063/1.460227 Comment on: Evaporation of covalent clusters: Unimolecular decay of energized sizeselected carbon cluster ions J. Chem. Phys. 94, 6933 (1991); 10.1063/1.460226 Infrared photodissociation of sizeselected methylamine clustersThe unimolecular decay of energized size-selected carbon clusters (C:,5 < n < 100) is investigated. The clusters are produced in a laser-generated plasma on the surface of a graphite rod. Directly extracted cations that decay on a ""S time scale are probed in a double-focusing, reverse-geometry mass spectrometer. The unimolecular decomposition rates are extracted from metastable fraction measurements. We observe a dramatic discontinuous increase in the decay rate constant as a function of cluster size around mass c 3 t (factor of 5 to 10). Additionally, low rate constants, relative to the neighbors, are found for cst, CJ;, and c 7 t. The results are rationalized by postulating a phase transition from small "rigid" clusters for n < 30 to larger "molten" entities for n > 30. In this model local deviations in rate constant reflect the thermodynamic stabilities of the clusters. A further consequence of this model is that "magic" numbers in the mass spectrum originate primarily from the intrinsic stability of the clusters with respect to evaporation and not from a kinetic growth mechanism.

Photofragmentation of C60

“…lc but this time the dominant fragmentation process is the loss of C~ with some contribution from single carbon atom loss. These results are in agreement with measurements of the photodissociation [13], collisionat dissociation [14] and metastable fragmentation [15] of small carbon cations where the dominant fragment was found to be C +_ 3 in each case.…”

“…4, and the loss of a single carbon atom to give the particularly stable n --19, 15, 11 species. The trend observed for the small fragments is in very good agreement with the trend in the rate constants obtained for unimotecular decay of small carbon clusters [15] and with the experimentally determined binding energies [14,17]. In particular, C~3 has a particularly low binding energy due to its anti-aromatic character (4n rr electrons).…”

Fragmentation ofC60: Experimental detection of C,C2,Lykke1 1995Phys. Rev. A401140View full textAdd to dashboardCite

“…Geusic et al [30] and Radi et al [31,32] have shown that C3 loss is the predominant dissociation pathway for a majority of the small (n (30) carbon clusters, although C and C2 do originate from a small fraction of these clusters. However, C,4 -C60 were given as the only possible candidates for losing C4.…”

Correlation between the latent heats and cohesive energies of metal clusters

“…[1][2][3][4][5][6][7][8][9] This is the correct approach for the very small clusters that behave like molecules and do not melt. However, it is now well established that even relatively small metal clusters can undergo a meltinglike transition with a significant latent heat.…”