Orbital-mediated tunneling

Mazur U, Hipps KW (1999) Orbital-mediated tunneling, inelastic electron tunneling, and electrochemical potentials formetal phthalocyanine thin films. J Phys Chem B103 9721-9727... 

Elastic tunneling spectroscopy is discussed in the context of processes involving molecular ionization and electron affinity states, a technique we call orbital mediated tunneling spectroscopy, or OMTS. OMTS can be applied readily to M-I-A-M and M-I-A-I -M systems, but application to M-A-M junctions is problematic. Spectra can be obtained from single molecules. Ionization state results correlate well with UPS spectra obtained from the same systems in the same environment. Both ionization and affinity levels measured by OMTS can usually be correlated with one electron oxidation and reduction potentials for the molecular species in solution. OMTS can be identified by peaks in dl/dV vs bias voltage plots that do not occur at the same position in either bias polarity. Because of the intrinsic... 

Fig. 10 Electrochemical energy level model for orbital mediated tunneling. Ap and Ac are the gas-and crystalline-phase electron affinities, 1/2(SCE) is the electrochemical potential referenced to the saturated calomel electrode, and provides the solution-phase electron affinity. Ev, is the Fermi level of the substrate (Au here). The corresponding positions in the OMT spectrum are shown by Ar and A0 and correspond to the electron affinity and ionization potential of the adsorbate film modified by interaction with the supporting metal, At. The spectrum is that of nickel(II) tetraphenyl-porphyrin on Au (111). (Reprinted with permission from [26])...

Mazur U, Hipps KW (1994) Unoccupied orbital mediated tunneling resonance-like structures in the tunneling spectra of polyacenes. J Phys Chem 98 5824—5829... 

Deng W, Hipps KW (2003) Tip-sample distance dependence in the STM-based orbital-mediated tunneling spectrum of nickel(II) tetraphenylporphyrin deposited on Au(lll). J Phys Chem B 107 10736-10740... 

Scudiero L, Barlow DE, Mazur U, Hipps KW (2001) Scanning tunneling microscopy, orbital mediated tunneling spectroscopy, and ultraviolet photoelectron spectroscopy of metal(II) tetraphenylporphyrins deposited from vapor. J Am Chem Soc 123 4073 1080... 

Barlow DE, Scudiero L, Hipps KW (2004) An STM study of the structure and orbital mediated tunneling spectra of CoPc and CoTPP on Au(lll) mixed composition films. Langmuir 20 4413 1421... 

Gyarfas B, Wiggins B, Hipps KW (2010) Temperature independence of orbital mediated tunneling in cobalt(II) phthalocyanine. J Phys Chem C 114 13349-13353... 

Standard Reduction Potentials (in Nonaqueous Solvents) and Adjusted First Orbital-Mediated Tunneling (OMT) Band Position (in t)) in a Variety of Compounds... 

The total current I through a molecule has an inelastic contribution /)ets from excitation of molecular vibrations (the main goal of IETS) (Fig. 11.25) and can have also an elastic contribution, which consists of two parts the off-resonance elastic ohmic IR (shown in the center part of Fig. 11.26) and a resonant elastic contribution Iomt between the Fermi59 level of the relevant metal electrode and an unoccupied molecular orbital of the molecule this part has been dubbed orbital-mediated tunneling (OMT) (Fig. 11.26) [11] ... 

One technique recently applied to UE [129,130] is inelastic electron tunneling spectroscopy (IETS) (Section 11.11). The IETS spectrum (dIz/dVz) measured at 4.2 K for a monolayer of fullerene-fczs-[12a.ethylthio-tetrakis(3,4-dibutyl-2-thiophene-5-ethenyl)-5-bromo-3,4-dibu-tyl-2-thiophene] malo-nate, 47, between Al and Pb electrodes [130] exhibited (i) the usual IETS spectrum of intramolecular vibrations and (ii) an elastic component, measured at slightly higher bias V, due to "orbital-mediated tunneling," that is, an... 

Hipps, K.W., Barlow, D.E., and Mazur, U., Orbital mediated tunneling spectroscopy of VOPc, Abstr. Pap. Am. Chem. Soc. 219, U840-U840, 2000. 

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