Phonon and plasmon excitation in inelastic electron tunneling spectroscopy of graphite

The inelastic electron tunneling spectrum (IETS)of highly oriented pyrolitic graphite (HOPG) has been measured with scanning tunneling spectroscopy (STS) at 6K. The observed spectral features are in very good agreement with the vibrational density of states (vDOS) of graphite calculated from first principles. We discuss the enhancement of certain phonon modes by phonon-assisted tunneling in STS based on the restrictions imposed by the electronic structure of graphite. We also demonstrate for the first time the local excitation of surface-plasmons in IETS which are detected at an energy of 40 meV.Comment: PRB rapid communication, submitte

A triple-resonance pulse scheme for selectively correlating amide 1 H N and 15 N nuclei with the 1 H α proton of the preceding residue

A 3D 1 H− 15 N− 13 C triple resonance experiment is presented that contains exclusively cross peaks between the 1 H N and 15 N nuclei of one residue with the H α of the preceding residue. The pulse sequence, designed to minimize the time coherence, is transverse on nuclei with short T 2 values. The experiment consists of coherence transfers via one-bond couplings from the H N via N, CO, C α to the H α and back to the H N for detection; it is called HN(COCA)HA. The experiment was tested on uniformly 15 N- and 13 C-enriched T4 lysozyme.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43044/1/10858_2005_Article_BF01874816.pd