1,246 research outputs found
Optimizing aerodynamic lenses for single-particle imaging
A numerical simulation infrastructure capable of calculating the flow of gas
and the trajectories of particles through an aerodynamic lens injector is
presented. The simulations increase the fundamental understanding and predict
optimized injection geometries and parameters. Our simulation results were
compared to previous reports and also validated against experimental data for
500 nm polystyrene spheres from an aerosol-beam- characterization setup. The
simulations yielded a detailed understanding of the radial phase-space
distribution and highlighted weaknesses of current aerosol injectors for
single-particle diffractive imaging. With the aid of these simulations we
developed new experimental implementations to overcome current limitations
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
Spatially-controlled complex molecules and their applications
The understanding of molecular structure and function is at the very heart of
the chemical and molecular sciences. Experiments that allow for the creation of
structurally pure samples and the investigation of their molecular dynamics and
chemical function have developed tremendously over the last few decades,
although "there's plenty of room at the bottom" for better control as well as
further applications.
Here, we describe the use of inhomogeneous electric fields for the
manipulation of neutral molecules in the gas-phase, \ie, for the separation of
complex molecules according to size, structural isomer, and quantum state. For
these complex molecules, all quantum states are strong-field seeking, requiring
dynamic fields for their confinement. Current applications of these controlled
samples are summarised and interesting future applications discussed.Comment: Accepted by Int. Rev. Phys. Che
Development and characterization of a laser-induced acoustic desorption source
A laser-induced acoustic desorption source, developed for use at central
facilities, such as free-electron lasers, is presented. It features prolonged
measurement times and a fixed interaction point. A novel sample deposition
method using aerosol spraying provides a uniform sample coverage and hence
stable signal intensity. Utilizing strong-field ionization as a universal
detection scheme, the produced molecular plume is characterized in terms of
number density, spatial extend, fragmentation, temporal distribution,
translational velocity, and translational temperature. The effect of desorption
laser intensity on these plume properties is evaluated. While translational
velocity is invariant for different desorption laser intensities, pointing to a
non-thermal desorption mechanism, the translational temperature increases
significantly and higher fragmentation is observed with increased desorption
laser fluence.Comment: 8 pages, 7 figure
First observation of electric-quadrupole infrared transitions in water vapour
Molecular absorption of infrared radiation is generally due to ro-vibrational
electric-dipole transitions. Electric-quadrupole transitions may still occur,
but they are typically a million times weaker than electric-dipole transitions,
rendering their observation extremely challenging. In polyatomic or polar
diatomic molecules, ro-vibrational quadrupole transitions have never been
observed. Here, we report the first direct detection of quadrupole transitions
in water vapor. The detected quadrupole lines have intensity largely above the
standard dipole intensity cut-off of spectroscopic databases and thus are
important for accurate atmospheric and astronomical remote sensing
The future of marine biodiversity and marine ecosystem functioning in UK coastal and territorial waters (including UK Overseas Territories) – with an emphasis on marine macrophyte communities
Funding from the UK Natural Environment Research Council (NERC) through Oceans 2025 (WP4.5), Funder Id: 10.13039/501100000270, Grant Number: Oceans 2025 – WP 4.5 and the MASTS pooling initiative (Marine Alliance for Science and Technology for Scotland, funded by the Scottish Funding Council and contributing institutions; grant reference HR09011) is gratefully acknowledged.Peer reviewedPublisher PD
Characterizing and optimizing a laser-desorption molecular beam source
The design and characterization of a new laser-desorption molecular beam
source, tailored for use in x-ray-free-electron-laser and
ultrashort-pulse-laser imaging experiments, is presented. It consists of a
single mechanical unit containing all source components, including the
molecular-beam valve, the sample, and the fiber-coupled desorption laser, which
is movable in five axes, as required for experiments at central facilities.
Utilizing strong-field ionization, we characterize the produced molecular beam
and evaluate the influence of desorption laser pulse energy, relative timing of
valve opening and desorption laser, sample bar height, and which part of the
molecular packet is probed on the sample properties. Strong-field ionization
acts as a universal probe and allows to detect all species present in the
molecular beam, and hence enables us to analyze the purity of the produced
molecular beam, including molecular fragments. We present optimized
experimental parameters for the production of the purest molecular beam,
containing the highest yield of intact parent ions, which we find to be very
sensitive to the placement of the desorbed-molecules plume within the
supersonic expansion
New perspectives in time-resolved laser-induced electron diffraction
Imaging the microscopic world in real space and real time is a grand challenge of science. In the landscape of time-resolved imaging techniques, laser-induced electron diffraction (LIED) has recently shown to be a promising candidate to push the frontiers of ultrafast molecular imaging. In this work, we review the main achievements of LIED research in terms of experimental results and advanced modelling. We also envision interesting perspectives toward the future advancement of time-resolved LIED imaging
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