85 research outputs found
Electrostatic trapping of metastable NH molecules
We report on the Stark deceleration and electrostatic trapping of NH
() radicals. In the trap, the molecules are excited on the
spin-forbidden transition and detected via
their subsequent fluorescence to the ground state. The 1/e
trapping time is 1.4 0.1 s, from which a lower limit of 2.7 s for the
radiative lifetime of the state is deduced. The spectral
profile of the molecules in the trapping field is measured to probe their
spatial distribution. Electrostatic trapping of metastable NH followed by
optical pumping of the trapped molecules to the electronic ground state is an
important step towards accumulation of these radicals in a magnetic trap.Comment: replaced with final version, added journal referenc
Loading Stark-decelerated molecules into electrostatic quadrupole traps
Beams of neutral polar molecules in a low-field seeking quantum state can be
slowed down using a Stark decelerator, and can subsequently be loaded and
confined in electrostatic quadrupole traps. The efficiency of the trap loading
process is determined by the ability to couple the decelerated packet of
molecules into the trap without loss of molecules and without heating. We
discuss the inherent difficulties to obtain ideal trap loading, and describe
and compare different trap loading strategies. A new "split-endcap" quadrupole
trap design is presented that enables improved trap loading efficiencies. This
is experimentally verified by comparing the trapping of OH radicals using the
conventional and the new quadrupole trap designs
Stark deceleration of CaF molecules in strong- and weak-field seeking states
We report the Stark deceleration of CaF molecules in the strong-field seeking
ground state and in a weak-field seeking component of a rotationally-excited
state. We use two types of decelerator, a conventional Stark decelerator for
the weak-field seekers, and an alternating gradient decelerator for the
strong-field seekers, and we compare their relative merits. We also consider
the application of laser cooling to increase the phase-space density of
decelerated molecules.Comment: 10 pages, 8 figure
Optical pumping of trapped neutral molecules by blackbody radiation
Optical pumping by blackbody radiation is a feature shared by all polar
molecules and fundamentally limits the time that these molecules can be kept in
a single quantum state in a trap. To demonstrate and quantify this, we have
monitored the optical pumping of electrostatically trapped OH and OD radicals
by room-temperature blackbody radiation. Transfer of these molecules to
rotationally excited states by blackbody radiation at 295 K limits the
trapping time for OH and OD in the state to
2.8 s and 7.1 s, respectively.Comment: corrected small mistakes; added journal reference
Optimizing the Stark-decelerator beamline for the trapping of cold molecules using evolutionary strategies
We demonstrate feedback control optimization for the Stark deceleration and
trapping of neutral polar molecules using evolutionary strategies. In a
Stark-decelerator beamline pulsed electric fields are used to decelerate OH
radicals and subsequently store them in an electrostatic trap. The efficiency
of the deceleration and trapping process is determined by the exact timings of
the applied electric field pulses. Automated optimization of these timings
yields an increase of 40 % of the number of trapped OH radicals.Comment: 7 pages, 4 figures (RevTeX) (v2) minor corrections (v3) no changes to
manuscript, but fix author list in arXiv abstrac
Slowing polar molecules using a wire Stark decelerator
We have designed and implemented a new Stark decelerator based on wire
electrodes, which is suitable for ultrahigh vacuum applications. The 100
deceleration stages are fashioned out of 0.6 mm diameter tantalum and the
array's total length is 110 mm, approximately 10 times smaller than a
conventional Stark decelerator with the same number of electrode pairs. Using
the wire decelerator, we have removed more than 90% of the kinetic energy from
metastable CO molecules in a beam.Comment: updated version, added journal referenc
Reflection of OH molecules from magnetic mirrors
We have reflected a Stark-decelerated beam of OH molecules under normal
incidence from mirrors consisting of permanent magnets. Two different types of
magnetic mirrors have been demonstrated. A long-range flat mirror made from a
large disc magnet has been used to spatially focus the reflected beam in the
longitudinal direction ("bunching"). A short-range curved mirror composed of an
array of small cube magnets allows for transverse focusing of the reflected
beam.Comment: 10 pages, 5 figure
Observation of Quantum Effects in sub Kelvin Cold Reactions
There has been a long-standing quest to observe chemical reactions at low
temperatures where reaction rates and pathways are governed by quantum
mechanical effects. So far this field of Quantum Chemistry has been dominated
by theory. The difficulty has been to realize in the laboratory low enough
collisional velocities between neutral reactants, so that the quantum wave
nature could be observed. We report here the first realization of merged
neutral supersonic beams, and the observation of clear quantum effects in the
resulting reactions. We observe orbiting resonances in the Penning ionization
reaction of argon and molecular hydrogen with metastable helium leading to a
sharp increase in the absolute reaction rate in the energy range corresponding
to a few degrees kelvin down to 10 mK. Our method is widely applicable to many
canonical chemical reactions, and will enable a breakthrough in the
experimental study of Quantum Chemistry
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