Atom tunneling

Gamarnik A, Johnson B A and Garcia-Garibay M A 1998 Effect of solvents on the photoenolization of omicron-methylanthrone at low temperatures. Evidence for H-atom tunneling from nonequilibrating triplets J. Rhys. Chem. A102 5491... 

In the H/D isotope effect case, m2/wi = 2, the interval of temperatures between re(H) and re(D) is wider than AT as predicted by (2.19), and in this interval the H atom tunnels while the D atom classically overcomes the barrier. For this reason the isotope effect becomes several orders larger than that described by (2.70). At 7" < 7 c(m2) the tunneling isotope effect becomes independent of the temperature. 

Quantum-chemical calculations of PES for carbonic acid dimers [Meier et al. 1982] have shown that at fixed heavy-atom coordinates the barrier is higher than 30kcal/mol, and distance between O atoms is 2.61-2.71 A. Stretching skeleton vibrations reduce this distance in the transition state to 2.45-2.35 A, when the barrier height becomes less than 3 kcal/mol. Meier et al. [1982] have stressed that the transfer is possible only due to the skeleton deformation, which shortens the distances for the hydrogen atom tunneling from 0.6-0.7 A to 0.3 A. The effective tunneling mass exceeds 2mn-... 

Figure 12. Tunneling to the alternative state at energy e. can be accompanied by a distortion of the domain boundary and thus populating the ripplon states. The doubled circles denote atomic tunneling displacements. The dashed hne signifies, say, the lowest energy state of the wall, and the dashed circles correspond to the respective atomic displacements. An alternative wall s state is shown by dash-dotted lines the corresponding alternative sets of atomic motions are coded by dash-dotted lines. The domain boundary distortion is diown in an exagerated fashion. The boundary does not have to lie in between atoms and is drawn this way for the sake of argument its position in fact is not tied to the atomic locations in an a priori obvious fashion.

Cyclobutadiene—Heavy Atom Tunneling Without Intersystem Crossing 431... 

Thus, these results indicated the involvement of heavy atom tunneling in the localized biradicals. The rates of decay for 19,20, and 9 could be fitted with Bell s simple model of tunneling through a parabolic barrier. Assuming log A (s ) = 8.0, and... 

M. Sponsler, R. Jain, F. Corns, and D. A. Dougherty, Matrix-isolation decay kinetics of triplet cyclobutanediyls. Ohservation of both Arrhenius behavior and heavy-atom tunneling in C-C bond-forming reactions, J. Am. Chem. Soc. 1989, 111, 2240. 

In the last century, many microstructural characterization techniques have been developed, such as electron microscopy, atomic tunneling microscopy, photoelectron spectroscopy, Raman spectroscopy, etc. The structure of the OLED-based displays is such that many pixels are arranged orderly in the x-y plane. The size and number of pixels determine the resolution and size of the display. Along the z-axis, several layers are stacked on each other. These layers... 

Heavy atom tunneling of entire alkyl groups between the different sides of the hydrogen bonded ring plane is much less likely even for methanol, in contrast to the analogous but fighter water case [108]. These motions correspond to hindered rotation of the monomer and are slowed down considerably in the complex due to the librational constraints. 

These data led to the model already described several times above. The enzyme executes a search for a tunneling sub-state, apparently 13 kcaFmol in energy above the principal state from this state the hydrogen atom tunnels with no further vibrational excitation. Probably motion of the secondary center is coupled into the tunneling coordinate. The result is large, temperature-independent primary and secondary isotope effects in the context of an isotope-independent activation energy. 

Kuznetsov, A.M. and Ulstrup, J. (1999). Proton and hydrogen atom tunnelling in hydrol3dic and redox enzyme catalysis. Can. J. Chem. 77, 1085-1096... 

C Kinetic Deuterium Isotope Effects and H Atom Tunnelling in the... 

AM of the coupling arises, for example, for radiative-decay modulation due to atomic motion through a high-Q cavity or a photonic crystal [68,69], or for atomic tunneling in optical lattices with time-varying lattice acceleration [59,70], Let the coupling be turned on and off periodically, for the time and tq -, respectively,... 

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