32 research outputs found
Slow and velocity-tunable beams of metastable He by multistage Zeeman deceleration
Metastable helium molecules (He) have been generated by striking a
discharge in a supersonic expansion of helium gas from a pulsed valve. When
operating the pulsed valve at room temperature, 77K, and 10K, the mean velocity
of the supersonic beam was measured to be 1900m/s, 980m/s, and 530m/s,
respectively. A 55-stage Zeeman decelerator operated in a phase-stable manner
was then used to further reduce the beam velocity and tune it in the range
between 100 and 150m/s. The internal-state distribution of the decelerated
sample was established by photoionization spectroscopy.Comment: 10 pages, 7 figure
Getting a Grip on the Transverse Motion in a Zeeman Decelerator
Zeeman deceleration is an experimental technique in which inhomogeneous,
time-dependent magnetic fields generated inside an array of solenoid coils are
used to manipulate the velocity of a supersonic beam. A 12-stage Zeeman
decelerator has been built and characterized using hydrogen atoms as a test
system. The instrument has several original features including the possibility
to replace each deceleration coil individually. In this article, we give a
detailed description of the experimental setup, and illustrate its performance.
We demonstrate that the overall acceptance in a Zeeman decelerator can be
significantly increased with only minor changes to the setup itself. This is
achieved by applying a rather low, anti-parallel magnetic field in one of the
solenoid coils that forms a temporally varying quadrupole field, and improves
particle confinement in the transverse direction. The results are reproduced by
three-dimensional numerical particle trajectory simulations thus allowing for a
rigorous analysis of the experimental data. The findings suggest the use of a
modified coil configuration to improve transverse focusing during the
deceleration process.Comment: accepted by J. Chem. Phy
Cavity-Enhanced Rayleigh Scattering
We demonstrate Purcell-like enhancement of Rayleigh scattering into a single
optical mode of a Fabry-Perot resonator for several thermal atomic and
molecular gases. The light is detuned by more than an octave, in this case by
hundreds of nanometers, from any optical transition, making particle excitation
and spontaneous emission negligible. The enhancement of light scattering into
the resonator is explained quantitatively as an interference effect of light
waves emitted by a classical driven dipole oscillator. Applications of our
method include the sensitive, non-destructive in-situ detection of ultracold
molecules.Comment: v2: 13 pages, 7 figures, small changes to the text, extended
description of the theoretical mode
Collisional effects in the formation of cold guided beams of polar molecules
High fluxes of cold polar molecules are efficiently produced by electric
guiding and velocity filtering. Here, we investigate different aspects of the
beam formation. Variations of the source parameters such as density and
temperature result in characteristic changes in the guided beam. These are
observed in the velocity distribution of the guided molecules as well as in the
dependence of the signal of guided molecules on the trapping electric field. A
model taking into account velocity-dependent collisional losses of cold
molecules in the region close to the nozzle accurately reproduces this
behavior. This clarifies an open question on the parameter dependence of the
detected signal and gives a more detailed understanding of the velocity
filtering and guiding process
Cavity-Enhanced Rayleigh Scattering
We demonstrate Purcell-like enhancement of Rayleigh scattering into a single
optical mode of a Fabry-Perot resonator for several thermal atomic and
molecular gases. The light is detuned by more than an octave, in this case by
hundreds of nanometers, from any optical transition, making particle excitation
and spontaneous emission negligible. The enhancement of light scattering into
the resonator is explained quantitatively as an interference effect of light
waves emitted by a classical driven dipole oscillator. Applications of our
method include the sensitive, non-destructive in-situ detection of ultracold
molecules.Comment: v2: 13 pages, 7 figures, small changes to the text, extended
description of the theoretical mode
Multistage Zeeman deceleration of metastable neon
A supersonic beam of metastable neon atoms has been decelerated by exploiting
the interaction between the magnetic moment of the atoms and time-dependent
inhomogeneous magnetic fields in a multistage Zeeman decelerator. Using 91
deceleration solenoids, the atoms were decelerated from an initial velocity of
580m/s to final velocities as low as 105m/s, corresponding to a removal of more
than 95% of their initial kinetic energy. The phase-space distribution of the
cold, decelerated atoms was characterized by time-of-flight and imaging
measurements, from which a temperature of 10mK was obtained in the moving frame
of the decelerated sample. In combination with particle-trajectory simulations,
these measurements allowed the phase-space acceptance of the decelerator to be
quantified. The degree of isotope separation that can be achieved by multistage
Zeeman deceleration was also studied by performing experiments with pulse
sequences generated for Ne and Ne.Comment: 16 pages, 15 figure
Knowledge Combination Analysis Reveals That Artificial Intelligence Research Is More Like "Normal Science" Than "Revolutionary Science"
Spectroscopy of formaldehyde in the 30140-30790cm^-1 range
Room-temperature absorption spectroscopy of formaldehyde has been performed
in the 30140-30790cm^-1 range. Using tunable ultraviolet continuous-wave laser
light, individual rotational lines are well resolved in the Doppler-broadened
spectrum. Making use of genetic algorithms, the main features of the spectrum
are reproduced. Spectral data is made available as Supporting Information
Sisyphus Cooling of Electrically Trapped Polyatomic Molecules
The rich internal structure and long-range dipole-dipole interactions
establish polar molecules as unique instruments for quantum-controlled
applications and fundamental investigations. Their potential fully unfolds at
ultracold temperatures, where a plethora of effects is predicted in many-body
physics, quantum information science, ultracold chemistry, and physics beyond
the standard model. These objectives have inspired the development of a wide
range of methods to produce cold molecular ensembles. However, cooling
polyatomic molecules to ultracold temperatures has until now seemed
intractable. Here we report on the experimental realization of opto-electrical
cooling, a paradigm-changing cooling and accumulation method for polar
molecules. Its key attribute is the removal of a large fraction of a molecule's
kinetic energy in each step of the cooling cycle via a Sisyphus effect,
allowing cooling with only few dissipative decay processes. We demonstrate its
potential by reducing the temperature of about 10^6 trapped CH_3F molecules by
a factor of 13.5, with the phase-space density increased by a factor of 29 or a
factor of 70 discounting trap losses. In contrast to other cooling mechanisms,
our scheme proceeds in a trap, cools in all three dimensions, and works for a
large variety of polar molecules. With no fundamental temperature limit
anticipated down to the photon-recoil temperature in the nanokelvin range, our
method eliminates the primary hurdle in producing ultracold polyatomic
molecules. The low temperatures, large molecule numbers and long trapping times
up to 27 s will allow an interaction-dominated regime to be attained, enabling
collision studies and investigation of evaporative cooling toward a BEC of
polyatomic molecules