107 research outputs found
Spatially separated polar samples of the cis and trans conformers of 3-fluorophenol
We demonstrate the spatial separation of the cis- and trans-conformers of
3-fluorophenol in the gas phase based on their distinct electric dipole
moments. For both conformers we create very polar samples of their
lowest-energy rotational quantum states. A >95 % pure beam of
trans-3-fluorophenol and a >90 % pure beam of the lowest-energy rotational
states of the less polar cis-3-fluorophenol were obtained for helium and neon
supersonic expansions, respectively. This is the first demonstration of the
spatial separation of the lowest-energy rotational states of the least polar
conformer, which is necessary for strong alignment and orientation of all
individual conformers.Comment: 5 pages, 5 figure
Knife edge skimming for improved separation of molecular species by the deflector
A knife edge for shaping a molecular beam is described to improve the spatial
separation of the species in a molecular beam by the electrostatic deflector.
The spatial separation of different molecular species from each other as well
as from atomic seed gas is improved. The column density of the selected
molecular-beam part in the interaction zone, which corresponds to higher signal
rates, was enhanced by a factor of 1.5, limited by the virtual source size of
the molecular beam.Comment: 3 pages, 2 figure
Long-term trapping of Stark-decelerated molecules
Trapped cold molecules represent attractive systems for precision-spectroscopic studies and for investigations of cold collisions and chemical reactions. However, achieving their confinement for sufficiently long timescales remains a challenge. Here, we report the long-term trapping of Stark-decelerated OH radicals in their X (2)Pi(3/2) (nu = 0, J = 3/2, M-J = 3/2, f) state in a permanent magnetic trap. The trap environment is cryogenically cooled to a temperature of 17 K to suppress black-body-radiation-induced pumping of the molecules out of trappable quantum states and collisions with residual background gas molecules which usually limit the trap lifetime. The cold molecules are thus confined on timescales approaching minutes, an improvement of up to two orders of magnitude compared with room temperature experiments, at translational temperatures of similar to 25 mK. The present results pave the way for new experiments using trapped cold molecules in precision spectroscopy, in studies of slow chemical processes at low energies and in the quantum technologies
Photophysics of indole upon x-ray absorption
A photofragmentation study of gas-phase indole (CHN) upon
single-photon ionization at a photon energy of 420 eV is presented. Indole was
primarily inner-shell ionized at its nitrogen and carbon orbitals.
Electrons and ions were measured in coincidence by means of velocity map
imaging. The angular relationship between ionic fragments is discussed along
with the possibility to use the angle-resolved coincidence detection to perform
experiments on molecules that are strongly oriented in their recoil-frame. The
coincident measurement of electrons and ions revealed
fragmentation-pathway-dependent electron spectra, linking the structural
fragmentation dynamics to different electronic excitations. Evidence for
photoelectron-impact self-ionization was observed.Comment: 11 pages, 6 figure
Spatial separation of pyrrole and pyrrole-water clusters
We demonstrate the spatial separation of pyrrole and pyrrole(HO) clusters
from the other atomic and molecular species in a supersonically-expanded beam
of pyrrole and traces of water seeded in high-pressure helium gas. The
experimental results are quantitatively supported by simulations. The obtained
pyrrole(HO) cluster beam has a purity of ~100 %. The extracted rotational
temperature of pyrrole and pyrrole(HO) from the original supersonic
expansion is K, whereas the temperature of the
deflected, pure-pyrrole(HO) part of the molecular beam corresponds to
K
Spin-State Transition and Metal-Insulator Transition in LaEuCoO}
We present a study of the structure, the electric resistivity, the magnetic
susceptibility, and the thermal expansion of LaEuCoO. LaCoO
shows a temperature-induced spin-state transition around 100 K and a
metal-insulator transition around 500 K. Partial substitution of La by
the smaller Eu causes chemical pressure and leads to a drastic increase
of the spin gap from about 190 K in LaCoO to about 2000 K in EuCoO, so
that the spin-state transition is shifted to much higher temperatures. A
combined analysis of thermal expansion and susceptibility gives evidence that
the spin-state transition has to be attributed to a population of an
intermediate-spin state with orbital order for and without orbital
order for larger . In contrast to the spin-state transition, the
metal-insulator transition is shifted only moderately to higher temperatures
with increasing Eu content, showing that the metal-insulator transition occurs
independently from the spin-state distribution of the Co ions. Around
the metal-insulator transition the magnetic susceptibility shows a similar
increase for all and approaches a doping-independent value around 1000 K
indicating that well above the metal-insulator transition the same spin state
is approached for all .Comment: 10 pages, 6 figure
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