26 research outputs found
Multiple cavity experiments to detect parity nonconservation in atomic hydrogen
We develop general guidelines and criteria for designing and evaluating beam experiments which use Ramsey's method of separated oscillating fields to detect PNC (parity nonconserving) effects in atomic hydrogen. We find that variation of the relative radio-frequency phases between different field configurations may offer distinct advantages in measuring and processing expected PNC data. We evaluate several specific experiments employing such multiple region designs.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23951/1/0000198.pd
Memory Effects in Spontaneous Emission Processes
We consider a quantum-mechanical analysis of spontaneous emission in terms of
an effective two-level system with a vacuum decay rate and
transition angular frequency . Our analysis is in principle exact,
even though presented as a numerical solution of the time-evolution including
memory effects. The results so obtained are confronted with previous
discussions in the literature. In terms of the {\it dimensionless} lifetime
of spontaneous emission, we obtain deviations from
exponential decay of the form for the decay amplitude as
well as the previously obtained asymptotic behaviors of the form or for . The actual
asymptotic behavior depends on the adopted regularization procedure as well as
on the physical parameters at hand. We show that for any reasonable range of
and for a sufficiently large value of the required angular frequency
cut-off of the electro-magnetic fluctuations, i.e. , one obtains either a or a
dependence. In the presence of physical boundaries, which can change the decay
rate with many orders of magnitude, the conclusions remains the same after a
suitable rescaling of parameters.Comment: 13 pages, 5 figures and 46 reference
Atoms in Flight and the Remarkable Connections between Atomic and Hadronic Physics
Atomic physics and hadron physics are both based on Yang Mills gauge theory;
in fact, quantum electrodynamics can be regarded as the zero-color limit of
quantum chromodynamics. I review a number of areas where the techniques of
atomic physics provide important insight into the theory of hadrons in QCD. For
example, the Dirac-Coulomb equation, which predicts the spectroscopy and
structure of hydrogenic atoms, has an analog in hadron physics in the form of
light-front relativistic equations of motion which give a remarkable first
approximation to the spectroscopy, dynamics, and structure of light hadrons.
The renormalization scale for the running coupling, which is unambiguously set
in QED, leads to a method for setting the renormalization scale in QCD. The
production of atoms in flight provides a method for computing the formation of
hadrons at the amplitude level. Conversely, many techniques which have been
developed for hadron physics, such as scaling laws, evolution equations, and
light-front quantization have equal utility for atomic physics, especially in
the relativistic domain. I also present a new perspective for understanding the
contributions to the cosmological constant from QED and QCD.Comment: Presented at EXA2011, the International Conference on Exotic Atoms
and Related Topics, Vienna, September 5-9, 201
Precision physics of simple atoms: QED tests, nuclear structure and fundamental constants
Quantum electrodynamics is the first successful and still the most successful
quantum field theory. Simple atoms, being essentially QED systems, allow highly
accurate theoretical predictions. Because of their simple spectra, such atoms
have been also efficiently studied experimentally frequently offering the most
precisely measured quantities. Our review is devoted to comparison of theory
and experiment in the field of precision physics of light simple atoms. In
particular, we consider the Lamb shift in the hydrogen atom, the hyperfine
structure in hydrogen, deuterium, helium-3 ion, muonium and positronium, as
well as a number of other transitions in positronium. Additionally to a
spectrum of unperturbed atoms, we consider annihilation decay of positronium
and the g factor of bound particles in various two-body atoms. Special
attention is paid to the uncertainty of the QED calculations due to the
uncalculated higher-order corrections and effects of the nuclear structure. We
also discuss applications of simple atoms to determination of several
fundamental constants
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Arcing and rf signal generation during target irradiation by a high-energy, pulsed neutral particle beam
We present a theory describing the dynamics of arc discharges in bulk dielectric materials on board space-based vehicles. Such ''punch-through'' arcs can occur in target satellites irradiated by high-energy (250 MeV), pulsed (100 mA x 10 ms) neutral particle beams. We treat the arc as a capacitively limited avalanche current in the target dielectric material, and we find expressions for the arc duration, charge transport, currents, and discharge energy. These quantities are adjusted to be consistent with known scaling laws for the area of charge depleted by the arc. After a brief account of the statistical distribution of voltages at which the arc starts and stops, we calculate the signal strength and frequency spectrum of the electromagnetic radiation broadcast by the arc. We find that arcs from thick ()similarreverse arrowto)1 cm) targets can generate rf signals detectable up to 1000 km from the target, bu a radio receiver operating at frequency 80 MHz, bandwidth 100 kHz, and detection threshold -105 dBm. These thick-target arc signals are 10 to 20 dB above ambient noise at the receiver, and they provide target hit assessment if the signal spectrum can be sampled at several frequencies in the nominal range 30-200 MHz. Thin-target ()similarreverse arrowto)1 mm) arc signals are much weaker, but when they are detecable in conjunction with thick-target signals, target discrimination is possible by comparing the signal frequency spectra. 24 refs., 12 figs