Unimolecular Double Photoionization-Induced Processes in Iron Pentacarbonyl

Abstract

The dissociations of nascent Fe(CO) 5 ++ ions created by 40.81 eV photoionization of iron pentacarbonyl have been examined using threefold and fourfold electron–ion coincidence measurements. The energies and forms of the ions have been explored by high-level calculations, revealing several new structures. The most stable form of Fe(CO) 5 ++ has a quite different geometry from that of the neutral molecule. The dissociation pattern can be modeled as a sequence of CO evaporations followed by two-body charge separations. Each Fe(CO) n ++ ( n = 1–4) dication is stable in a restricted energy range; as its internal energy increases, it first ejects a neutral CO, then loses CO + by charge separation at higher energy. In the initial stages, charge-retaining CO evaporations dominate over charge separation, but the latter become more competitive as the number of residual CO ligands decreases. At energies where ionization is mainly from the CO ligands, new Fe–C and C–C bonds are created by a mechanism which might be relevant to catalysis by Fe.

Fragmentation dynamics of CH3Clq+ (q = 2,3): theory and experiment

“…For other molecular systems, such experiments combined with advanced theoretical treatments allowed elucidating the unimolecular state-to-state reaction pathways undertaken by the doubly changed molecular ions formed by valence double photoionization of the corresponding neutral. 46,47,49,50…”

Electron-induced dissociation dynamics studied using covariance-map imaging

“…The existence of such ions is oen revealed in time-of-ight (ToF) measurements by long "tails" on the corresponding ion ToF peaks, caused by the ions dissociating as they traverse the eld-free ight tube aer clearing the extraction region of the mass spectrometer. [35][36][37] A number of techniques have been used to study the unimolecular decay of multiply-charged ions, including tandem mass spectrometry, [38][39][40][41][42] photoelectronphotoion-photoion coincidence (PEPIPICO) [43][44][45][46][47] and covariance-map imaging. 31,36,[48][49][50][51] Covariance analysis of multimass velocity-map imaging datasets is a powerful technique which allows correlations between ions formed from the same individual molecule or cluster to be observed.…”

“…A number of techniques have been used to study the unimolecular decay of multiply-charged ions, including tandem mass spectrometry, 38–42 photoelectron–photoion–photoion coincidence (PEPIPICO) 43–47 and covariance-map imaging. 31,36,48–51 Covariance analysis of multimass velocity-map imaging datasets is a powerful technique which allows correlations between ions formed from the same individual molecule or cluster to be observed.…”

Coincidence study of core-ionized adamantane: site-sensitivity within a carbon cage?

“…Thus we have studied the dissociation of adamantane molecules in the gas phase after C-1s core-ionization using synchrotron X-ray radiation and explore site-sensitive dissociation. In fact, K-shell ionization by synchrotron radiation has been extensively used to probe the chemical environment of many molecular and cluster systems [25][26][27][28][29][30][31][32][33] even though site-specific dissociation is often considered as weak 34 and that fragmentation dynamics is mostly driven by internal energy 35,36 . The fact that adaman-tane is a saturated hydrocarbon implies that the detection of siteselective dissociation (using the direct photoelectron) is highly challenging due to small energy difference between the two different carbon sites (similar chemical environment) and the effect is expected to be rather small.…”