Vibrational Sum Frequency Generation Spectroscopy Measurement of the Rotational Barrier of Methyl Groups on Methyl-Terminated Silicon(111) Surfaces.
| Autor: | Bhattacharyya D; Department of Chemistry , University of Southern California , Los Angeles , California 90089-0482 , United States., Montenegro A; Department of Chemistry , University of Southern California , Los Angeles , California 90089-0482 , United States., Plymale NT; Division of Chemistry and Chemical Engineering, and Beckman Institute , California Institute of Technology , Pasadena , California 91125 , United States., Dutta C; Department of Chemistry , University of Southern California , Los Angeles , California 90089-0482 , United States., Lewis NS; Division of Chemistry and Chemical Engineering, and Beckman Institute , California Institute of Technology , Pasadena , California 91125 , United States., Benderskii AV; Department of Chemistry , University of Southern California , Los Angeles , California 90089-0482 , United States. |
|---|---|
| Jazyk: | angličtina |
| Zdroj: | The journal of physical chemistry letters [J Phys Chem Lett] 2019 Sep 19; Vol. 10 (18), pp. 5434-5439. Date of Electronic Publication: 2019 Sep 03. |
| DOI: | 10.1021/acs.jpclett.9b01487 |
| Abstrakt: | The methyl-terminated Si(111) surface possesses a 3-fold in-plane symmetry, with the methyl groups oriented perpendicular to the substrate. The propeller-like rotation of the methyl groups is hindered at room temperature and proceeds via 120° jumps between three isoenergetic minima in registry with the crystalline Si substrate. We have used line-shape analysis of polarization-selected vibrational sum frequency generation spectroscopy to determine the rotational relaxation rate of the surface methyl groups and have measured the temperature dependence of the relaxation rate between 20 and 120 °C. By fitting the measured rate to an Arrhenius dependence, we extracted an activation energy (the rotational barrier) of 830 ± 360 cm -1 and an attempt frequency of (2.9 ± 4.2) × 10 13 s -1 for the methyl rotation process. Comparison with the harmonic frequency of a methyl group in a 3-fold cosine potential suggests that the hindered rotation occurs via uncorrelated jumps of single methyl groups rather than concerted gear-like rotation. |
| Databáze: | MEDLINE |
| Externí odkaz: |
|