31 research outputs found
Interaction of UV light with cold metastable helium atoms
Hogervorst, W. [Promotor]Vassen, W. [Copromotor
Infrared dynamic polarizability of HD+ rovibrational states
A calculation of dynamic polarizabilities of rovibrational states with
vibrational quantum number and rotational quantum number in the
1s ground-state potential of HD is presented. Polarizability
contributions by transitions involving other 1s rovibrational states
are explicitly calculated, whereas contributions by electronic transitions are
treated quasi-statically and partially derived from existing data [R.E. Moss
and L. Valenzano, \textit{Molec. Phys.}, 2002, \textbf{100}, 1527]. Our model
is valid for wavelengths m and is used to to assess level shifts due to
the blackbody radiation (BBR) electric field encountered in experimental
high-resolution laser spectroscopy of trapped HD ions. Polarizabilities of
1s rovibrational states obtained here agree with available existing
accurate \textit{ab initio} results. It is shown that the Stark effect due to
BBR is dynamic and cannot be treated quasi-statically, as is often done in the
case of atomic ions. Furthermore it is pointed out that the dynamic Stark
shifts have tensorial character and depend strongly on the polarization state
of the electric field. Numerical results of BBR-induced Stark shifts are
presented, showing that Lamb-Dicke spectroscopy of narrow vibrational optical
lines ( Hz natural linewidth) in HD will become affected by BBR
shifts only at the level
All-Optical Broadband Excitation of the Motional State of Trapped Ions
We have developed a novel all-optical broadband scheme for exciting,
amplifying and measuring the secular motion of ions in a radio frequency trap.
Oscillation induced by optical excitation has been coherently amplified to
precisely control and measure the ion's secular motion. Requiring only laser
line-of-sight, we have shown that the ion's oscillation amplitude can be
precisely controlled. Our excitation scheme can generate coherent motion which
is robust against variations in the secular frequency. Therefore, our scheme is
ideal to excite the desired level of oscillatory motion under conditions where
the secular frequency is evolving in time. Measuring the oscillation amplitude
through Doppler velocimetry, we have characterized the experimental parameters
and compared them with a molecular dynamics simulation which provides a
complete description of the system.Comment: 8 pages, 10 figure
Suitability of linear quadrupole ion traps for large Coulomb crystals
Growing and studying large Coulomb crystals, composed of tens to hundreds of
thousands of ions, in linear quadrupole ion traps presents new challenges for
trap implementation. We consider several trap designs, first comparing the
total driven micromotion amplitude as a function of location within the
trapping volume; total micromotion is an important point of comparison since it
can limit crystal size by transfer of radiofrequency drive energy into thermal
energy. We also compare the axial component of micromotion, which leads to
first-order Doppler shifts along the preferred spectroscopy axis in precision
measurements on large Coulomb crystals. Finally, we compare trapping potential
anharmonicity, which can induce nonlinear resonance heating by shifting normal
mode frequencies onto resonance as a crystal grows. We apply a non-deforming
crystal approximation for simple calculation of these anharmonicity-induced
shifts, allowing a straightforward estimation of when crystal growth can lead
to excitation of different nonlinear heating resonances. In the axial
micromotion and anharmonicity points of comparison, we find significant
differences between the compared trap designs, with an original rotated-endcap
trap performing slightly better than the conventional in-line endcap trap