1,436 research outputs found
Measurement of excited-state transitions in cold calcium atoms by direct femtosecond frequency-comb spectroscopy
We apply direct frequency-comb spectroscopy, in combination with precision cw
spectroscopy, to measure the transition
frequency in cold calcium atoms. A 657 nm ultrastable cw laser was used to
excite atoms on the narrow ( Hz) clock transition, and the direct output of the frequency comb was
used to excite those atoms from the state to the state. The resonance of this second stage was detected by observing a
decrease in population of the ground state as a result of atoms being optically
pumped to the metastable states. The transition frequency is measured to be kHz; which is an improvement by almost four orders of magnitude over
the previously measured value. In addition, we demonstrate spectroscopy on
magnetically trapped atoms in the state.Comment: 4 pages 5 figure
Non-equilibrium raft-like membrane domains under continuous recycling
We present a model for the kinetics of spontaneous membrane domain (raft)
assembly that includes the effect of membrane recycling ubiquitous in living
cells. We show that the domains have a broad power-law distribution with an
average radius that scales with the 1/4 power of the domain lifetime when the
line tension at the domain edges is large. For biologically reasonable
recycling and diffusion rates the average domain radius is in the tens of nm
range, consistent with observations. This represents one possible link between
signaling (involving rafts) and traffic (recycling) in cells. Finally, we
present evidence that suggests that the average raft size may be the same for
all scale-free recycling schemes.Comment: 8 pages, 5 figure
Relativistic recoil, electron-correlation, and QED effects on the 2p_j-2s transition energies in Li-like ions
The relativistic nuclear recoil, higher-order interelectronic-interaction,
and screened QED corrections to the transition energies in Li-like ions are
evaluated. The calculation of the relativistic recoil effect is performed to
all orders in 1/Z. The interelectronic-interaction correction to the transition
energies beyond the two-photon exchange level is evaluated to all orders in 1/Z
within the Breit approximation. The evaluation is carried out employing the
large-scale configuration-interaction Dirac-Fock-Sturm method. The rigorous
calculation of the complete gauge invariant sets of the screened self-energy
and vacuum-polarization diagrams is performed utilizing a local screening
potential as the zeroth-order approximation. The theoretical predictions for
the 2p_j-2s transition energies are compiled and compared with available
experimental data in the range of the nuclear charge number Z=10-60.Comment: 39 pages, 3 figures, 11 table
Finite Temperature Lattice QCD with Clover Fermions
We report on our simulation of finite temperature lattice QCD with two
flavors of Symanzik-improved fermions and
Symanzik-improved glue. Our thermodynamic simulations were performed on an lattice, and we have performed complementary zero temperature
simulations on an lattice. We compare our results to those from
simulations with two flavors of Wilson fermions and discuss the improvement
resulting from use of the improved action.Comment: 3 pages, 4 figures, Talk presented at Lattice 9
Exotic hybrid mesons with light quarks
Hybrid mesons, made from a quark, an antiquark and gluons, can have quantum
numbers inaccessible to conventional quark-antiquark states. Confirmation of
such states would give information on the role of "dynamical" color in low
energy QCD. We present preliminary results for hybrid meson masses using light
Wilson valence quarks.Comment: 4 pages, 4 figures, Talk presented at LATTICE96(spectrum
Update on the hadron spectrum with two flavors of staggered quarks
We present an update on the MILC Collaboration's light hadron spectrum
calculation with two flavors of dynamical, staggered quarks. We present
extrapolations of the nucleon to rho mass ratio to the continuum limit for
fixed values of the pi to rho mass ratio including the physical one.Comment: 3 pages, LaTex with espcrc2 and epsf, 5 postscript figures included,
Lattice '97 Proceeding
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