Molecular tunneling

Troisi A, Ratner MA (2007) Inelastic insights for molecular tunneling pathways bypassing the terminal groups. PCCP 9(19) 2421-2427... 

I am not familiar with the results you mentioned. Looking for the biochemical studies that have directly confirmed our observation of molecular tunneling in chemical reactions, one should mention the investigations of the dynamics of ligand rebinding to heme proteins performed by H. Frauenfelder, I. Gunsalus, and their colleagues at the University of Illinois (Urbana, 111.) [see, e.g., Biochemistry, 14, 5355 (1975) and Science, 192, 1002 (1976)]. 

One interesting analogy should be noted here. It is well known that the exponential factor that determines the rate of tunneling contains the product d. JmE, where d is the barrier width, E is its height, and m is the mass of tunneling particle. In chemical cases in ours and American works, d 10 8-5cm, m 30, E 0, 1 eV. In the spontaneous fission of nuclei, d 10 12 cm, m 100, E 106 eV. Thus the spontaneous fission of nuclei and molecular tunneling in chemical reactions can be treated to some extent as quite similar phenomena. 

The experiments on the radiation-induced solid-state formaldehyde polymerization at 140 to 4°K were the first to demonstrate the molecular tunneling (i.e., the tunneling of whole molecules and/or molecular groups). 

The next example of molecular tunneling near absolute zero was the rebinding of ligands to heme proteins that I have already mentioned. The typical distances of electron tunneling in various (e.g., radiation-chemical) oxidation reduction processes in solid state at 100 to 140°K are of the order of tens of angstroms. Distances of molecular tunneling at about 4°K are equal to 0.3 to 0.5 A. 

As an example of the NEGF-DFT formalism discussed in the last section, we now report an analysis on the transport properties of an Au-Ceo-Au molecular tunnel junction whose device structure is shown in the lower panel of Fig. 1. So far a considerable amount of effort has been devoted to investigate transport properties of Ceo and other fullerene molecules both experimentally [54-59] and theoretically [25,60-62]. However, to obtain a complete picture of the transport properties of such junctions, many details have yet to be clarified, including how conductance and I-V curves depend on the lead material and geometry, and on the position and orientation of the Cgo molecule. Ceo tunnel junctions with Au leads have not been studied before. 

As an example, some details of transport features of Au-Cgo-Au molecular tunnel junctions were discussed. The physical mechanism of resonance transmission through the molecule was responsible for most of the transport properties. The resonance is mediated by the LUMO-derived states, and charge transfer plays a very important role. The I-V curves show metallic... 

In this work, we present a brief introduction to the nonequilibrium Green s function method and discuss two important examples in which nonequli-brium Green s functions can be employed (1) electric current calculations in molecular tunneling devices and (2) in quantum dot-sensitized solar cells. 

Yu. Dahnovsky, Electron-electron correlations in molecular tunnel junctions A diagrammatic approach, Phys. Rev. B 80 (2009) 165305. 

The earliest example of a non-peptidic channel model was prepared by Tabushi et al.28 It consisted of a P-cyclodextrin, attached to four hydrophobic tails designed to afford a half-channel. The transport of copper and cobalt was assessed in artificial liposomes (kCo(n) = 4.5 x 10 4s-1), the rate being much faster than in the absence of the half-channel. In the same year, Lehn29 reported a solid-state model of a molecular tunnel consisting of stacked macrocyclic polyethers, with K+ ions located alternatively inside and on top of successive macrocycles. 

Seideman, T. and Guo, H. (2003) Quantum transport and current-triggered dynamics in molecular tunnel junctions. J. Theor. Comput. Chem., 2, 439-458. 

As a final example, the internal rotor CH3OH shows not one but a whole series of band spectra arising from molecular tunnelling through the barrier to internal rotation. These are spread through both centimetre and MMW bands, and have been extensively studied, e.g. by Xu and Lovas, following on initial work by Lees and Baker. ... 

Jiang, L., Sangeeth, C.S.S., Yuan, L., Thompson, D., Nijhuis, C.A. One-nanometer thin monolayers remove the deleterious effect of substrate defects in molecular tunnel junctions. Nano Lett. (2015)... 

Molecular tunnelling processes have been detected in the recombination of HbCO after flash photolysis at low temperature ( < 10 K) and attempts to analyse the data using non-adiabatic molecular group transfer theory have met with reasonable success. At higher temperatures, (< 20 K) a non-exponential Arrhenius pathway is detected suggesting a distribution of activation enthalpies depend-... 

While UPS provides a valuable characterization, it does not enable the measurement of a barrier in a completed MJ. In order to provide such information, a method termed internal photoemission (IPE), which had been used to measure tunneling barriers in oxide tunnel junctions [172-174], has been proposed for use in determining molecular tunnel junction barriers for intact MJs [175]. In this case, absorption of light by the molecule must be carefully considered, but... 

Kim, B., Choi, S.FL, Zhu, X.Y., and Frisbie, C.D. (2011) Molecular tunnel junctions based on pi-conjugated oligoacene thiols and dithiols between Ag, Au, and Pt contacts effect of surface linking group and metal work function. J. Am. Chem. Soc., 133, 19864-19877. 

Charge transport in molecular electronic junctions compression of the molecular tunnel barrier in the strong coupling regime. Proc. Natl. Acad. Sci. U.S.A., 109, 11498-11503. 

Fereiro, J., McCreery, R.L., and Bergren, A.J. (2013) Direct optical determination of interfacial transport barriers in molecular tunnel junctions. J. Am. Chem. Soc., 135, 9584-9587. 

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