2,591 research outputs found
Nanoscopy of pairs of atoms by fluorescence in a magnetic field
Spontaneous emission spectra of two initially excited closely spaced
identical atoms are very sensitive to the strength and the direction of the
applied magnetic field. The relevant schemes are considered that ensure the
determination of the mutual spatial orientation of the atoms and the distance
between them by entirely optical means. A corresponding theoretical description
is given accounting for the dipole-dipole interaction between the two atoms in
the presence of a magnetic field and for polarizations of the quantum field
interacting with magnetic sublevels of the two-atom system
Giant acceleration in slow-fast space-periodic Hamiltonian systems
Motion of an ensemble of particles in a space-periodic potential well with a
weak wave-like perturbation imposed is considered. We found that slow
oscillations of wavenumber of the perturbation lead to occurrence of directed
particle current. This current is amplifying with time due to giant
acceleration of some particles. It is shown that giant acceleration is linked
with the existence of resonant channels in phase space
The Threshold effects for the two-particle Hamiltonians on lattices
For a wide class of two-body energy operators on the three-dimensional
lattice \bbZ^3, being the two-particle quasi-momentum, we prove that if
the following two assumptions (i) and (ii) are satisfied, then for all
nontrivial values , , the discrete spectrum of below its
threshold is non-empty. The assumptions are:
(i) the two-particle Hamiltonian corresponding to the zero value of
the quasi-momentum has either an eigenvalue or a virtual level at the bottom of
its essential spectrum and (ii) the one-particle free
Hamiltonians in the coordinate representation generate positivity preserving
semi-groups
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