Showing papers by "Thalappil Pradeep published in 1996"
TL;DR: In this article, a surface-induced dissociation (SID) prior to new bond formation was demonstrated for low-energy CH n + (n = 0-4) ions with a fluorinated self-assembled monolayer (F-SAM) surface.
Abstract: Reactive scattering of low-energy (<100 eV) CH n + (n = 0-4) ions with a fluorinated self-assembled monolayer (F-SAM) surface produces fluorine-containing scattered ions, including CF + , C 2 HF 2 + and C 3 F 3 + . Evidence is provided that these ion-surface reactions occur by surface-induced dissociation (SID) prior to new bond formation. Chemical sputtering of the ion-beam modified surface is consistent with the modification of the fluorinated SAM surface by the methane derived ions occurring at the terminal CF 3 group. Studies with 13 C-labeled ions show the formation of 12 CF + and 13 CF + in nearly equal abundance. The participation of carbon atoms arising from both the surface and the projectile suggests the intermediacy of a symmetrical fluoronium collision complex, such as [F 13 CF 12 CF] + , involving the SID fragments of the projectile and the terminal CF 3 group of the surface. A 20% translational to vibrational (T → V) energy conversion is estimated from the inelastic collisions which lead to SID, a result which is consistent with previous studies using other ions on the same surface
17 citations
TL;DR: In this article, it is suggested that the surface modification involves the substitution of the ion/surface reaction sites with the appropriate reagent and that the extent of modification is limited to the top layers of the surface.
8 citations
TL;DR: In this paper, the electron spin resonance (esr) of C60 and HMTTEF has been investigated at 9.36 GHz as a function of temperature and the Curie-Weiss plots of inverse esr absorption intensity versus temperature indicate an antiferromagnetic TH = 50 for air exposed C60, and 90K for C60Ox.
Abstract: The electron spin resonance (esr) of C60.Ox and C60.HMTTEF (hexamethylentetratellurafulvalene) has been investigated at 9.36 GHz as a function of temperature. T (298 T 4 K). C60.Ox shows an esr absorption of equal ‘g’ value to that of C60 exposed to O2 and light but is more intense. The C60 in its pure form is in a singlet state. The impurity sites introduced by O2 produce the esr absorption. The Curie - Weiss plots of inverse esr absorption intensity versus temperature indicate an antiferromagnetic TH = 50 for air exposed C60 and 90K for C60Ox. From the esr intensity at room temperature, the calculated number of free spins (S = 1/2) is =1/3 per mole of C60-Ox. In case of C60.HMTTEF, there is a very weak esr absorption at room temperature suggesting that the room temperature form is diamagnetic with very small charge transfer between C60 and HMTTEF. This conclusion is consistent with the structure and magnetic susceptibility of this cocrystal. As the temperature is lowered, the equilibrium: AD <=...
2 citations