Hyperthermal Energy Collisions of CF3+ Ions With Modified Surfaces: Surface-Induced Dissociation
The dissociative scattering of low-energy ions, especially polyatomic ions, from surfaces has become an active area of research in chemistry, physics and material sciences. The interaction between an ion and a surface is more complicated than ion and gaseous neutral collisions and needs to be explored in detail to understand the ion excitation and dissociation phenomena associated with Surface-induced dissociation (SID) of ions, a technique used for the analysis of high mass ions from biological molecules. However, dynamics studies of SID have been performed only for a few simple systems, viz., ethanol, acetone, benzene and carbon disulfide ions. We have therefore undertaken a study of the SID of a small polyatomic ion, CF3+, at several collision energies between 28.8 eV and 159 eV in collision with fluorinated alkyl thiol on gold 111 crystal. These experiment were performed using a custom built tandem mass spectrometer where the energy and intensity distributions of the scattered fragment ions were measured as a function of the fragment mass and scattering angle. In contrast with the previous studies of the SID of ethanol and acetone cations where the inelastically scattered primary ions dominated the collision process (up to {approx}50 eV maximum energy used in those experiments), we did not observe a measurable abundance of inelastically scattered undissociated CF3+ ions up to the lowest energy studied here. We observed all fragment ions, CF2+, CF+, F+ and C+ at all energies studied with the relative intensity of the highest energy pathway, C+, increasing with collision energy. Also, the SID efficiency decreased significantly as the collision energy was increased from 106 eV to 159 eV. The energy distributions of all the fragment ions showed two distinct components, one corresponding to the loss of nearly all of the kinetic energy and scattered over a broad angular range while the other corresponding to smaller kinetic energy losses and scattered closer to the surface parallel. The latter process is due to delayed dissociation of excited ions after they have passed the collision region and the energy analyzer as excited parent ions.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 15020713
- Report Number(s):
- PNNL-SA-39298; TRN: US200521%%104
- Journal Information:
- Journal of Undergraduate Research, Vol. 4
- Country of Publication:
- United States
- Language:
- English
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