1,192 research outputs found
The potential role of kelp forests on iodine speciation in coastal seawater
Funding: FCK would like to thank the TOTAL Foundation (Paris) and the MASTS pooling initiative (The Marine Alliance for Science and Technology for Scotland) for their support. MASTS is funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions. JG acknowledges support from an SDSU Research Foundation Summer Undergraduate Research Award. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD
Making the best of mixed-field orientation of polar molecules: A recipe for achieving adiabatic dynamics in an electrostatic field combined with laser pulses
We have experimentally and theoretically investigated the mixed-field
orientation of rotational-state-selected OCS molecules and we achieve strong
degrees of alignment and orientation. The applied moderately intense nanosecond
laser pulses are long enough to adiabatically align molecules. However, in
combination with a weak dc electric field, the same laser pulses result in
nonadiabatic dynamics in the mixed-field orientation. These observations are
fully explained by calculations employing, both, adiabatic and non-adiabatic
time-dependent models.Comment: 5 pages, 4 figure
Strongly driven quantum pendulum of the OCS molecule
We demonstrate and analyze a strongly driven quantum pendulum in the angular
motion of stateselected and laser aligned OCS molecules. Raman-couplings during
the rising edge of a 50-picosecond laser pulse create a wave packet of pendular
states, which propagates in the confining potential formed by the
polarizability interaction between the molecule and the laser field. This
wave-packet dynamics manifests itself as pronounced oscillations in the degree
of alignment with a laser-intensity dependent period.Comment: 6 pages, 4 figure
Free Radicals in Superfluid Liquid Helium Nanodroplets: A Pyrolysis Source for the Production of Propargyl Radical
An effusive pyrolysis source is described for generating a continuous beam of
radicals under conditions appropriate for the helium droplet pick-up method.
Rotationally resolved spectra are reported for the vibrational mode of
the propargyl radical in helium droplets at 3322.15 cm. Stark spectra
are also recorded that allow for the first experimental determination of the
permanent electric dipole moment of propargyl, namely -0.150 D and -0.148 D for
ground and excited state, respectively, in good agreement with previously
reported ab initio results of -0.14 D [1]. The infrared spectrum of the
mode of propargyl-bromide is also reported. The future application of these
methods for the production of novel radical clusters is discussed
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
Controlling rotation in the molecular-frame with an optical centrifuge
We computationally demonstrate a new method for coherently controlling the
rotation-axis direction in asymmetric top molecules with an optical centrifuge.
Appropriately chosen electric-field strengths and the centrifuge's acceleration
rate allow to generate a nearly arbitrary rotational wavepacket. For DS and
2H-imidazole (CHN) we created wavepackets at large values of the
rotational quantum number with the desired projections of the total angular
momentum onto two of the molecules' principal axes of inertia. One application
of the new method is three-dimensional alignment with a molecular axis aligned
along the laser's wave vector, which is important for the three-dimensional
imaging of molecules yet not accessible in standard approaches. The
simultaneous orientation of the angular momentum in the laboratory frame and in
the molecular frame could also be used in robust control of scattering
experiments
Atome im Karussell
Detaillierte Untersuchungen nukleophiler Substitutionsreaktionen zeigen einen neuen elementaren Reaktionskanal auf
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
- …