48 research outputs found
Relativistic corrections of m\alpha^6 order to the ro-vibrational spectrum of H_2^+ and HD^+ molecular ions
The major goal of the high-precision studies of ro-vibrational states in the
hydrogen molecular ions is to provide an alternative way for improving the
electron-to-proton mass ratio, or the atomic mass of electron. By now the
complete set of relativistic and radiative corrections have been obtained for a
wide range of ro-vibrational states of H_2^+ and HD^+ up to order
R_\infty\alpha^4. In this work we complete calculations of various
contributions to the R_\infty\alpha^4 order by computing the relativistic
corrections to the binding energy of electron.Comment: 4 pages, 1 figur
Proposed method for laser spectroscopy of pionic helium atoms to determine the charged-pion mass
Metastable pionic helium () is a three-body atom composed of a
helium nucleus, an electron occupying the ground state, and a negatively
charged pion in a Rydberg state with principal- and orbital angular
momentum quantum numbers of . We calculate the
spin-independent energies of the and
isotopes in the region --19. These include relativistic and quantum
electrodynamics corrections of orders and
in atomic units, where and denote
the Rydberg and fine structure constants. The fine-structure splitting due to
the coupling between the electron spin and the orbital angular momentum of the
, and the radiative and Auger decay rates of the states are also
calculated. Some states and retain
nanosecond-scale lifetimes against absorption into the helium nucleus.
We propose to use laser pulses to induce transitions from these
metastable states, to states with large ( s) Auger rates.
The ion that remains after Auger emission of the
electron undergoes Stark mixing with the , , and states during
collisions with the helium atoms in the experimental target. This leads to
immediate nuclear absorption of the . The resonance condition between
the laser beam and the atom is thus revealed as a sharp spike in the rates of
neutrons, protons, deuterons, and tritons that emerge....(continued)Comment: 25 pages, 3 tables, 11 figure
Calculation of the relativistic Bethe logarithm in the two-center problem
We present a variational approach to evaluate relativistic corrections of
order \alpha^2 to the Bethe logarithm for the ground electronic state of the
Coulomb two center problem. That allows to estimate the radiative contribution
at m\alpha^7 order in molecular-like three-body systems such as hydrogen
molecular ions H_2^+ and HD^+, or antiprotonic helium atoms. While we get 10
significant digits for the nonrelativistic Bethe logarithm, calculation of the
relativistic corrections is much more involved especially for small values of
bond length R. We were able to achieve a level of 3-4 significant digits
starting from R=0.2 bohr, that will allow to reach 10^{-10} relative
uncertainty on transition frequencies.Comment: 19 pages, 5 tables, 7 figure
Calculation of transition probabilities and ac Stark shifts in two-photon laser transitions of antiprotonic helium
Numerical ab initio variational calculations of the transition probabilities
and ac Stark shifts in two-photon transitions of antiprotonic helium atoms
driven by two counter-propagating laser beams are presented. We found that
sub-Doppler spectroscopy is in principle possible by exciting transitions of
the type (n,L)->(n-2,L-2) between antiprotonic states of principal and angular
momentum quantum numbers n~L-1~35, first by using highly monochromatic,
nanosecond laser beams of intensities 10^4-10^5 W/cm^2, and then by tuning the
virtual intermediate state close (e.g., within 10-20 GHz) to the real state
(n-1,L-1) to enhance the nonlinear transition probability. We expect that ac
Stark shifts of a few MHz or more will become an important source of systematic
error at fractional precisions of better than a few parts in 10^9. These shifts
can in principle be minimized and even canceled by selecting an optimum
combination of laser intensities and frequencies. We simulated the resonance
profiles of some two-photon transitions in the regions n=30-40 of the
\bar{p}^4He^+ and \bar{p} ^3He^+ isotopes to find the best conditions that
would allow this.Comment: 18 pages 2 tables 12 figures, submitted to Phys. Rev.