Quantum tunneling effect

Truong T N 1997 Thermal rates of hydrogen exchange of methane with zeolite a direct ab initio dynamics study on the importance of quantum tunneling effects J. Rhys. Chem. B 101 2750... 

On the other hand, the proton potential of the 5-bromo compound is exactly symmetrical with reference to the reaction coordinate of the tautomerization. Consequently, the proton transfer can proceed through the tunnelling mechanism. This is the reason why the paraelectric behaviour is maintained even at 4 K. The suppression of the antiferroelectric phase transition may be derived from a quantum tunnelling effect. Such paraelectric behaviour can be regarded as quantum paraelectricity , which is a notion to designate the phenomenon that (anti)ferroelectric phase transitions are suppressed even at cryogenic temperatures due to some quantum-mechanical stabilization, proton tunnelling in this case. 

Our discussion has focused on barriers in the range available via the usual DNMR methods. There are specialized approaches that allow determination of lower barriers usually found in most single bond rotations, such as methyl rotation.Note that investigations of very low barriers involving groups with hydrogen nuclei may need to consider quantum tunneling effects. 

FIGURE 3.4 The fitting of the quantum tunneling effect based computed universal half-life times for nuclei emitting alpha particles with their observed values for representative radioactive series adapted from (Rohlf, 1994 HyperPhysics, 2010). 

Nanoparticles have been widely used in optical, resonant, electrical, and magnetic fields. The small size effect, large surface effect, and quantum tunnel effect demonstrate the unique properties of nanoparticles. It is necessary to study the techniques of nanoparticle preparation to meet the developments in nanotechnology and nanomaterials. In this section, we describe work carried out in our laboratory on the syntheses of several nanoparticles and nanocomposites and the study of their properties. 

Analysis of isotope effects on H thermal desorption spectra on Pd(lll) has also evidenced a pathway of direct H entry into the bulk without equilibration with the chemisorption state [19]. However, this mechanism observed after H2/D2 exposure at 115 K is probably related to a quantum tunneling effect not operating at room temperature. Alternatively, it might be due to the presence of two types of surface entry sites on this particular face, one being more stable than the other for chemisorption (discussed later in the chapter). 

La20s is an important lanthanum oxide, which is widely used in various types of catalytic reactions like dehydrogenation, combustion, hydrogenation, selective oxidation, etc. The nanomaterials (nano-sized materials or nano ultrafine particle) are denoted as the materials with the particle size in the range of 1-100 nm. Due to the quantum size effect, small size effect, siuface effect and macroscopic quantum tunneling effect, nano ultrafine materials have become the hotspot in the researches of catalysts [9]. In comparison with micro-sized lanthanum oxide, the nano-sized one, due to its higher specific surface area, has exhibited outstanding catalytic properties [10],... 

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