Showing papers by "Thalappil Pradeep published in 1995"
TL;DR: The most significant conclusion of the study is that selective chemical modification of monolayer surfaces can be achieved by using reactive ion beams, which lead to new covalent bonds at the surface and in the scattered ions.
41 citations
TL;DR: In this paper, low energy ion-surface collisions with organic surfaces are reviewed in terms of the ions formed as studied by mass spectrometry, and chemical manipulation of the incident ion and the surface are both of interest.
Abstract: Low energy ion-surface collisions with organic surfaces are reviewed in terms of the ions formed as studied by mass spectrometry. Chemical manipulation of the incident ion and the surface are both of interest.
12 citations
Journal Article•
TL;DR: The chemistry of a new class of molecular clusters having closed cage structure, called metallocarbohedrenes or metcars, is described, discovered in mass spectrometry experiments by reacting laser-evaporated metal with hydrocarbons and cooling the reacton mixture in an inert atmosphere of helium.
Abstract: The chemistry of a new class of molecular clusters having closed cage structure, called metallocarbohedrenes or
metcars, is described. These molecules of general formula M8C12, where M is a metal, were discovered in mass spectrometry experiments. By reacting laser-evaporated metal with hydrocarbons and cooling the reacton mixture in an inert atmosphere of helium, a number of metcar ions containing Ti, V, Hf, Zr, Mo, Cr and F e have been produced by different workers. The chemistry of these ions is gradually unfolding with several groups putting efforts in experimental and theoretical studies.
12 citations
TL;DR: In this article, the NiH2*+ ion was observed to excite a low-energy vibrational mode of the molecular ion, resulting in cyclopentadienyl ring fusion to form CmH8 with the simultaneous transfer of two hydrogen atoms to Ni'+.
Abstract: The first experimental observation of the NiH2*+ ion is described. Concerted hydrogen rearrangement upon mild collisional activation of the nickelocene molecular ion in either ion/surface or gas-phase ion/molecule collisions yields NiH2,+. Changes in the intensity of NiH2,+ with variation of collision and electron impact energies suggest that the mechanism involves the excitation of a low-energy vibrational mode of the molecular ion, resulting in cyclopentadienyl ring fusion to form CmH8 with the simultaneous transfer of two hydrogen atoms to Ni'+. Attempts at the formation of NiH2*+ by direct insertion of Ni*+ into hydrogen gas or by dehydrogenation of an alkane were unsuccessful; however, oxidative addition of H2 to NiCp*+ was observed. Gas-phase reactions between NiCp„+ ( = 0—2) and 1,3or 1,4-cyclohexadiene (CHD) show the production of ionic Ni complexes which involve dehydrogenation processes. These products include Ni(C6H6)*+, NiCpH2*+, and polyligated complexes with benzene, CHD, and cyclopentadiene. These dehydrogenation reactions suggest that the dihydride might be important in the hydrogenation/dehydrogenation chemistry of nickel.
8 citations
TL;DR: Angle resolved X-ray photoelectron spectroscopy from a liquid perfluoropolyether showed that its surface is primarily composed of chain ends oriented nearly perpendicular to the surface as discussed by the authors.
8 citations
TL;DR: In this paper, the microscopic structures of perfluorinated polyether (PFPE) liquid surfaces are characterized by ion/surface collision experiments in a mass spectrometer and the results are compared to those obtained with a fluorinated self-assembled monolayer (F-SAM) surface.
Abstract: This study shows that reactive ion/surface collisions can provide information on the surface structure of molecular systems. The microscopic structures of perfluorinated polyether (PFPE) liquid surfaces are characterized by ion/surface collision experiments in a mass spectrometer and the results are compared to those obtained with a fluorinated self-assembled monolayer (F-SAM) surface. Low energy (< 100 eV) beams of W+ and W(CO)6
+ ions are used for surface-induced dissociation (SID) and ion/surface reactive scattering, while Xe+ and Kr+ beams are used for chemical sputtering experiments. Both the PFPE and F-SAM surfaces show similar SID fragments while reactions with W+ and W(CO)6
+ lead to the scattered metal ion with multiple fluorine atoms attached. The main peaks in chemical sputtering spectra are similar for both surfaces as well. Both hydrogen probe beams and chemical sputtering confirm that the liquid PFPE surface is nearly free of impurities. Our results on both surfaces also suggest that the CF3 group of the monomer units is most likely projected outward from the bulk of the liquid surface.
5 citations
TL;DR: The chemistry of metallocarbohedrenes, a class of molecular clusters having closed cage structure, is described in this article, where a number of metcar ions containing Ti, V, Hf, Zr, Mo, Cr and F e have been produced by different workers.
Abstract: The chemistry of a new class of molecular clusters having closed cage structure, called metallocarbohedrenes or
metcars, is described. These molecules of general formula M8C12, where M is a metal, were discovered in mass spectrometry experiments. By reacting laser-evaporated metal with hydrocarbons and cooling the reacton mixture in an inert atmosphere of helium, a number of metcar ions containing Ti, V, Hf, Zr, Mo, Cr and F e have been produced by different workers. The chemistry of these ions is gradually unfolding with several groups putting efforts in experimental and theoretical studies.
TL;DR: The analysis of high resolution synchrotron X-ray powder diffraction data of hexamethylenetetetratellurafulvalene (HMTTEF) showed that there is a nearly close-packed layer of C{sub 60} molecules in the {und ab} plane as mentioned in this paper.