625 research outputs found
Ionization Potential of the Helium Atom
Ground state ionization potential of the He^4 atom is evaluated to be 5 945
204 221 (42) MHz. Along with lower order contributions, this result includes
all effects of the relative orders alpha^4, alpha^3*m_e/m_alpha and
alpha^5*ln^2(alpha).Comment: 4 page
Precision Spectroscopy of Molecular Hydrogen Ions: Towards Frequency Metrology of Particle Masses
We describe the current status of high-precision ab initio calculations of
the spectra of molecular hydrogen ions (H_2^+ and HD^+) and of two experiments
for vibrational spectroscopy. The perspectives for a comparison between theory
and experiment at a level of 1 ppb are considered.Comment: 26 pages, 13 figures, 1 table, to appear in "Precision Physics of
Simple Atomic Systems", Lecture Notes in Physics, Springer, 200
Corrections to the Nonrelativistic Ground Energy of a Helium Atom
Considering the nuclear motion, the authors give out the nonrelativistic
ground energy of a helium atom by using a simple but effective variational wave
function with a flexible parameter . Based on this result, the relativistic
and radiative corrections to the nonrelativistic Hamiltonian are discussed. The
high precision value of the helium ground energy is evaluated to be -2.90338
a.u., and the relative error is 0.00034%.Comment: 8 pages, no figures, 2 table
High accuracy results for the energy levels of the molecular ions H2+, D2+ and HD+, up to J=2
We present a nonrelativistic calculation of the rotation-vibration levels of
the molecular ions H2+, D2+ and HD+, relying on the diagonalization of the
exact three-body Hamiltonian. The J=2 levels are obtained with a very high
accuracy of 10^{-14} a.u. (for most levels) representing an improvement by five
orders of magnitude over previous calculations. The accuracy is also improved
for the J=1 levels of H2+ and D2+ with respect to earlier works. Moreover, we
have computed the sensitivities of the energy levels with respect to the mass
ratios, allowing these levels to be used for metrological purposes.Comment: 11 page
Relativistic corrections of order m\alpha^6 to the two-center problem
Effective potentials of the relativistic m\alpha^6 order correction for the
ground state of the Coulomb two-center problem are calculated. They can be used
to evaluate the relativistic contribution of that order to the energies of
hydrogen molecular ions or metastable states of the antiprotonic helium atom,
where precision spectroscopic data are available. In our studies we use the
variational expansion based on randomly chosen exponents that permits to
achieve high numerical accuracy.Comment: 12 pages, 3 tables 2 figures; submitted to the Journal of Physics
First observation of two hyperfine transitions in antiprotonic He-3
We report on the first experimental results for microwave spectroscopy of the
hyperfine structure of antiprotonic He-3. Due to the helium nuclear spin,
antiprotonic He-3 has a more complex hyperfine structure than antiprotonic He-4
which has already been studied before. Thus a comparison between theoretical
calculations and the experimental results will provide a more stringent test of
the three-body quantum electrodynamics (QED) theory. Two out of four
super-super-hyperfine (SSHF) transition lines of the (n,L)=(36,34) state were
observed. The measured frequencies of the individual transitions are
11.12559(14) GHz and 11.15839(18) GHz, less than 1 MHz higher than the current
theoretical values, but still within their estimated errors. Although the
experimental uncertainty for the difference of these frequencies is still very
large as compared to that of theory, its measured value agrees with theoretical
calculations. This difference is crucial to be determined because it is
proportional to the magnetic moment of the antiproton.Comment: 8 pages, 6 figures, just published (online so far) in Physics Letters
Relativistic and Radiative Energy Shifts for Rydberg States
We investigate relativistic and quantum electrodynamic effects for
highly-excited bound states in hydrogenlike systems (Rydberg states). In
particular, hydrogenic one-loop Bethe logarithms are calculated for all
circular states (l = n-1) in the range 20 <= n <= 60 and successfully compared
to an existing asymptotic expansion for large principal quantum number n. We
provide accurate expansions of the Bethe logarithm for large values of n, for
S, P and circular Rydberg states. These three expansions are expected to give
any Bethe logarithms for principal quantum number n > 20 to an accuracy of five
to seven decimal digits, within the specified manifolds of atomic states.
Within the numerical accuracy, the results constitute unified, general formulas
for quantum electrodynamic corrections whose validity is not restricted to a
single atomic state. The results are relevant for accurate predictions of
radiative shifts of Rydberg states and for the description of the recently
investigated laser-dressed Lamb shift, which is observable in a strong
coherent-wave light field.Comment: 8 pages; RevTeX
Simplest Molecules as Candidates for Precise Optical Clocks
The precise measurement of transition frequencies in cold, trapped molecules has applications in fundamental physics, and extremely high accuracies are desirable. We determine suitable candidates by considering the simplest molecules with a single electron, for which the external-field shift corrections can be calculated theoretically with high precision. Our calculations show that H 2 ĂŸ exhibits particular transitions whose fractional systematic uncertainties may be reduced to 5 Ă 10 â17 at room temperature. We also generalize the method of composite frequencies, introducing tailored linear combinations of individual transition frequencies that are free of the major systematic shifts, independent of the strength of the external perturbing fields. By applying this technique, the uncertainty of the composite frequency is reduced compared to what is achievable with a single transition, e.g., to the 10 â18 range for HD ĂŸ . Thus, these molecules are of metrological relevance for future studies
Relativistic and QED corrections to the vibrational state of the molecular ion
Relativistic and QED corrections to the recently discovered first vibrational
state are presented. This state has an extremely small
nonrelativistic binding energy a.u. Its wave
functions has a maximum at a.u. and extends up to several
hundreds. It is shown that this state does not disappear if higher order
relativistic and QED corrections, including the Casimir--Polder effect, are
taken into account
- âŠ