45 research outputs found
Analytical matrix elements of the Uehling potential in three-body systems, and applications to exotic molecules
Exact analytical expressions for the matrix elements of the Uehling potential
in a basis of explicitly correlated exponential wave functions are presented.
The obtained formulas are then used to compute with an improved accuracy the
vacuum polarization correction to the binding energy of muonic and pionic
molecules, both in a first-order perturbative treatment and in a
nonperturbative approach. The first resonant states lying below the n=2
threshold are also studied, by means of the stabilization method with a real
dilatation parameter
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
Faraday optical isolator in the 9.2 m range for QCL applications
We have fabricated and characterized a n-doped InSb Faraday isolator in the
mid-IR range (9.2 m). A high isolation ratio of 30 dB with a
transmission over 80% (polarizer losses not included) is obtained at room
temperature. Further possible improvements are discussed. A similar design can
be used to cover a wide wavelength range (lambda ~ 7.5-30 m)
Sympathetic Cooling Simulations with a Variable Time Step
In this paper we present a new variable time step criterion for the
velocity-Verlet algorithm allowing to correctly simulate the dynamics of
charged particles exchanging energy via Coulomb collisions while minimising
simulation time. We present physical arguments supporting the use of the
criterion along with numerical results proving its validity. We numerically
show that ions with 18 meV initial energy can be
captured and sympathetically cooled by a Coulomb crystal of
and in less than 10 ms, an important result for the GBAR
project.Comment: LEAP 2016 proceedin
Two-photon spectroscopy of trapped HD ions in the Lamb-Dicke regime
We study the feasibility of nearly-degenerate two-photon rovibrational
spectroscopy in ensembles of trapped, sympathetically cooled hydrogen molecular
ions using a resonance-enhanced multiphoton dissociation (REMPD) scheme. Taking
advantage of quasi-coincidences in the rovibrational spectrum, the excitation
lasers are tuned close to an intermediate level to resonantly enhance
two-photon absorption. Realistic simulations of the REMPD signal are obtained
using a four-level model that takes into account saturation effects, ion
trajectories, laser frequency noise and redistribution of population by
blackbody radiation. We show that the use of counterpropagating laser beams
enables optical excitation in an effective Lamb-Dicke regime. Sub-Doppler lines
having widths in the 100 Hz range can be observed with good signal-to-noise
ratio for an optimal choice of laser detunings. Our results indicate the
feasibility of molecular spectroscopy at the accuracy level for
improved tests of molecular QED, a new determination of the proton-to-electron
mass ratio, and studies of the time (in)dependence of the latter.Comment: 16 pages, 17 figure
Cooling antihydrogen ions for the free-fall experiment GBAR
We discuss an experimental approach allowing to prepare antihydrogen atoms
for the GBAR experiment. We study the feasibility of all necessary experimental
steps: The capture of incoming ions at keV energies in a deep
linear RF trap, sympathetic cooling by laser cooled Be ions, transfer to a
miniaturized trap and Raman sideband cooling of an ion pair to the motional
ground state, and further reducing the momentum of the wavepacket by adiabatic
opening of the trap. For each step, we point out the experimental challenges
and discuss the efficiency and characteristic times, showing that capture and
cooling are possible within a few seconds.Comment: 10 pages, 5 figure
Narrow-line phase-locked quantum cascade laser in the 9.2 micron range
We report on the operation of a 50 mW continuous wave quantum cascade laser
(QCL) in the 9.2 micrometer range, phase locked to a single mode CO2 laser with
a tunable frequency offset. The wide free running emission spectrum of the QCL
(3-5 MHz) is strongly narrowed down to the kHz range making it suitable for
high resolution molecular spectroscopy.Comment: 4 page
Vibrational spectroscopy of H2+: precise evaluation of the Zeeman effect
We present an accurate computation of the g-factors of the hyperfine states
of the hydrogen molecular ion H2+. The results are in good agreement with
previous experiments, and can be tested further by rf spectroscopy. Their
implication for high-precision two-photon vibrational spectroscopy of H2+ is
also discussed. It is found that the most intense hyperfine components of
two-photon lines benefit from a very small Zeeman splitting
Vibrational spectroscopy of H2+: hyperfine structure of two-photon transitions
We present the computation of two-photon transition spectra between
ro-vibrational states of the H2+ molecular ion, including the effects of
hyperfine structure and excitation polarization. The reduced two-photon matrix
elements are obtained by means of a variational method. We discuss the
implications of our results for high-resolution spectroscopy of H2+