We study macroscopic quantum tunneling of the magnetic moment in a single-domain particle placed above the surface of a superconductor. Such a setup allows one to manipulate the height of the energy barrier, preserving the degeneracy of the ground state. The tunneling amplitude and the effect of the dissipation in the superconductor are computed.

Quantum tunneling between degenerate ground states through the central barrier of a potential is extended to excited states with the instanton method. This extension is achieved with the help of an LSZ reduction technique as in field theory and may be of importance in the study of macroscopic quantum phenomena in magnetic systems. Quantum effects on the macroscopic scale have attracted consider...

In enzymatic C-H activation by hydrogen tunneling, reduced barrier width is important for efficient hydrogen wave function overlap during catalysis. For native enzymes displaying nonadiabatic tunneling, the dominant reactive hydrogen donor-acceptor distance (DAD) is typically ca. 2.7 Å, considerably shorter than normal van der Waals distances. Without a ground state substrate-bound structure fo...

We describe a proposal to probe the quantum tunneling mechanism of an individual ion trapped in a double-well electromagnetic potential. The time-evolution of the probability of fluorescence measurement of the electronic ground state is employed to characterize the single-particle tunneling mechanism. The proposed scheme can be used to implement quantum information devices.

We report the first high resolution spectrum of a librational vibration for a water cluster. Four parallel bands of (H2O)3 were measured between 510 and 525 cm 21 using diode laser vibration– rotation–tunneling ~VRT! spectroscopy. The bands lie in the ‘‘librational band’’ region of liquid water and are assigned to the nondegenerate out of plane librational vibration. The observation of at least...

Installing stone columns in the ground is an effective improvement technique to increase the load bearing capacity and reduce the consolidation settlement of the loose or weak cohesive soils. In addition to the increase in the bearing capacity and reduction in the settlement, stone columns can accelerate the dissipation rate of the excess pore water pressure generated by the surcharge, which ex...

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