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Nat Commun ; 5: 3816, 2014 May 09.
Artigo em Inglês | MEDLINE | ID: mdl-24809410


Due to the generally delocalized nature of molecular valence orbitals, valence-shell spectroscopies do not usually allow to specifically target a selected atom in a molecule. However, in X-ray electron spectroscopy, the photoelectron momentum is large and the recoil angular momentum transferred to the molecule is larger when the photoelectron is ejected from a light atom compared with a heavy one. This confers an extreme sensitivity of the rotational excitation to the ionization site. Here we show that, indeed, the use of high-energy photons to photoionize valence-shell electrons of hydrogen chloride offers an unexpected way to decrypt the atomic composition of the molecular orbitals due to the rotational dependence of the photoionization profiles. The analysis of the site-specific rotational envelopes allows us to disentangle the effects of the two main mechanisms of rotational excitation, based on angular momentum exchange between the molecule and either the incoming photon or the emitted electron.

Spectrochim Acta A Mol Biomol Spectrosc ; 117: 276-83, 2014 Jan 03.
Artigo em Inglês | MEDLINE | ID: mdl-23998960


Poly(methylmetacrilate)-maghemite (PMMA-gamma-Fe2O3) hybrid material was studied by the electron stimulated ion desorption (ESID) techniques coupled with time-of-flight mass spectrometry (TOF-MS) and theoretical investigation about its fragmentation. Moreover, atomic force microscopy was utilized to characterize the morphology before and after ionic desorption. ESID results indicated differences of pattern fragmentation for different compositions of hybrid material in comparison with neat PMMA. Theoretical studies suggest that kinetics effects can take place in the fragmentation process and electrostatic contributions were important in the stabilization of PMMA on maghemite after the grafting process.

Elétrons , Compostos Férricos/química , Íons , Modelos Teóricos , Nanopartículas/química , Polimetil Metacrilato/química , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz , Espectrometria de Massas em Tandem