178 research outputs found
Excitation of the classical-limit state of an atom
We describe a technique designed to excite a classical-limit state of an atom. A picosecond electric field pulse converts a circular state into a Rydberg wave packet which is localized in all three dimensions and travels along a classical Kepler orbit with arbitrary ellipticity
Excitation of the classical-limit state of an atom
We describe a technique designed to excite a classical-limit state of an atom. A picosecond electric field pulse converts a circular state into a Rydberg wave packet which is localized in all three dimensions and travels along a classical Kepler orbit with arbitrary ellipticity
Spin-Orbit Pendulum: the Microscopic Stern-Gerlach Effect
The motion of a particle with a spin in spherical harmonic oscillator
potential with spin-orbit interaction is studied. We have focus our attention
on spatial motion of wave packets, giving a description complementary to motion
of spin discussed already in [1]. The particular initial conditions studied
here lead to the most transparent formulas and can be treated analytically. A
strong analogy with the Stern-Gerlach experiment is suggested. [1] R.Arvieu and
P.Rozmej, Phys.Rev.A50 (1994) 4376.Comment: 4 pages, LaTeX (precisely RevTeX), attached 4 complicated Postscript
figures , Paper submitted to Phys.Rev.
Long-Term Evolution and Revival Structure of Rydberg Wave Packets for Hydrogen and Alkali-Metal Atoms
This paper begins with an examination of the revival structure and long-term
evolution of Rydberg wave packets for hydrogen. We show that after the initial
cycle of collapse and fractional/full revivals, which occurs on the time scale
, a new sequence of revivals begins. We find that the structure of
the new revivals is different from that of the fractional revivals. The new
revivals are characterized by periodicities in the motion of the wave packet
with periods that are fractions of the revival time scale . These
long-term periodicities result in the autocorrelation function at times greater
than having a self-similar resemblance to its structure for times
less than . The new sequence of revivals culminates with the
formation of a single wave packet that more closely resembles the initial wave
packet than does the full revival at time , i.e., a superrevival
forms. Explicit examples of the superrevival structure for both circular and
radial wave packets are given. We then study wave packets in alkali-metal
atoms, which are typically used in experiments. The behavior of these packets
is affected by the presence of quantum defects that modify the hydrogenic
revival time scales and periodicities. Their behavior can be treated
analytically using supersymmetry-based quantum-defect theory. We illustrate our
results for alkali-metal atoms with explicit examples of the revival structure
for radial wave packets in rubidium.Comment: To appear in Physical Review A, vol. 51, June 199
Nucleophilic Functionalization of the Calix[6]arene Para- and Meta-Position via p‑Bromodienone Route
It is here demonstrated that the p-bromodienone route,
previously reported for calix[4]arenes, is also effective for the functionalization
of the calix[6]arene macrocycle. Thus, alcoholic O-nucleophiles can be
introduced at the calix[6]arene exo rim. In addition, the reaction of a
calix[6]arene p-bromodienone derivative with an actived aromatic substrate,
such as resorcinol, led to the first example of a meta-functionalized,
inherently chiral calix[6]arene derivativ
Time dependent partial waves and vortex rings in the dynamics of wave packets
We have found a new class of time dependent partial waves which are solutions
of time dependent Schr\"odinger equation for three dimensional harmonic
oscillator. We also showed the decomposition of coherent states of harmonic
oscillator into these partial waves. This decomposition appears perticularly
convenient for a description of the dynamics of a wave packet representing a
particle with spin when the spin--orbit interaction is present in the
hamiltonian. An example of an evolution of a localized wave packet into a torus
and backwards, for a particular initial conditions is analysed in analytical
terms and shown with a computer graphics.Comment: 10 pages, LaTeX, 6 postscript figures, submitted to J. Phys. A: Math.
Ge
Bubble propagation in a helicoidal molecular chain
We study the propagation of very large amplitude localized excitations in a
model of DNA that takes explicitly into account the helicoidal structure. These
excitations represent the ``transcription bubble'', where the hydrogen bonds
between complementary bases are disrupted, allowing access to the genetic code.
We propose these kind of excitations in alternative to kinks and breathers. The
model has been introduced by Barbi et al. [Phys. Lett. A 253, 358 (1999)], and
up to now it has been used to study on the one hand low amplitude breather
solutions, and on the other hand the DNA melting transition. We extend the
model to include the case of heterogeneous chains, in order to get closer to a
description of real DNA; in fact, the Morse potential representing the
interaction between complementary bases has two possible depths, one for A-T
and one for G-C base pairs. We first compute the equilibrium configurations of
a chain with a degree of uncoiling, and we find that a static bubble is among
them; then we show, by molecular dynamics simulations, that these bubbles, once
generated, can move along the chain. We find that also in the most unfavourable
case, that of a heterogeneous DNA in the presence of thermal noise, the
excitation can travel for well more 1000 base pairs.Comment: 25 pages, 7 figures. Submitted to Phys. Rev.
Resolved-sideband Raman cooling to the ground state of an optical lattice
We trap neutral Cs atoms in a two-dimensional optical lattice and cool them
close to the zero-point of motion by resolved-sideband Raman cooling. Sideband
cooling occurs via transitions between the vibrational manifolds associated
with a pair of magnetic sublevels and the required Raman coupling is provided
by the lattice potential itself. We obtain mean vibrational excitations
\bar{n}_x \approx \bar{n}_y \approx 0.01, corresponding to a population \sim
98% in the vibrational ground state. Atoms in the ground state of an optical
lattice provide a new system in which to explore quantum state control and
subrecoil laser coolingComment: PDF file, 13 pages including 3 figure
Minimum-Uncertainty Angular Wave Packets and Quantized Mean Values
Uncertainty relations between a bounded coordinate operator and a conjugate
momentum operator frequently appear in quantum mechanics. We prove that
physically reasonable minimum-uncertainty solutions to such relations have
quantized expectation values of the conjugate momentum. This implies, for
example, that the mean angular momentum is quantized for any
minimum-uncertainty state obtained from any uncertainty relation involving the
angular-momentum operator and a conjugate coordinate. Experiments specifically
seeking to create minimum-uncertainty states localized in angular coordinates
therefore must produce packets with integer angular momentum.Comment: accepted for publication in Physical Review
Radial Squeezed States and Rydberg Wave Packets
We outline an analytical framework for the treatment of radial Rydberg wave
packets produced by short laser pulses in the absence of external electric and
magnetic fields. Wave packets of this type are localized in the radial
coordinates and have p-state angular distributions. We argue that they can be
described by a particular analytical class of squeezed states, called radial
squeezed states. For hydrogenic Rydberg atoms, we discuss the time evolution of
the corresponding hydrogenic radial squeezed states. They are found to undergo
decoherence and collapse, followed by fractional and full revivals. We also
present their uncertainty product and uncertainty ratio as functions of time.
Our results show that hydrogenic radial squeezed states provide a suitable
analytical description of hydrogenic Rydberg atoms excited by short-pulsed
laser fields.Comment: published in Physical Review
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