Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userScattering of Stark-decelerated OH radicals with rare-gas atoms
303
0
0.0
(
0
)
Added by
Sebastiaan Y.T. van de Meerakker
Publication date
2011
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
We present a combined experimental and theoretical study on the rotationally inelastic scattering of OH ($X,^2Pi_{3/2}, J=3/2, f$) radicals with the collision partners He, Ne, Ar, Kr, Xe, and D$_2$ as a function of the collision energy between $sim 70$ cm$^{-1}$ and 400~cm$^{-1}$. The OH radicals are state selected and velocity tuned prior to the collision using a Stark decelerator, and field-free parity-resolved state-to-state inelastic relative scattering cross sections are measured in a crossed molecular beam configuration. For all OH-rare gas atom systems excellent agreement is obtained with the cross sections predicted by close-coupling scattering calculations based on accurate emph{ab initio} potential energy surfaces. This series of experiments complements recent studies on the scattering of OH radicals with Xe [Gilijamse emph{et al.}, Science {bf 313}, 1617 (2006)], Ar [Scharfenberg emph{et al.}, Phys. Chem. Chem. Phys. {bf 12}, 10660 (2010)], He, and D$_2$ [Kirste emph{et al.}, Phys. Rev. A {bf 82}, 042717 (2010)]. A comparison of the relative scattering cross sections for this set of collision partners reveals interesting trends in the scattering behavior.
rate research
Read More
Propylene oxide is one of the simplest organic chiral molecules and has attracted considerable interest from the scientific community a few years ago, when it was discovered in the interstellar medium. Here, we report a preliminary study on the interaction between propylene oxide and rare-gas atoms, specifically He, Ne, and Ar. The interaction potentials as a function of the distance between the center-of-mass of propylene oxide and the rare-gas-atom are calculated for fourteen leading configurations at CCSD(T)/aug-cc-pVDZ level of theory. Symmetry Adapted Perturbation Theory has been employed for the analysis of the intermolecular potential, revealing that most of the contribution is given by dispersion and exchange forces.
With a Stark decelerator, beams of neutral polar molecules can be accelerated, guided at a constant velocity, or decelerated. The effectiveness of this process is determined by the 6D volume in phase space from which molecules are accepted by the Stark decelerator. Couplings between the longitudinal and transverse motion of the molecules in the decelerator can reduce this acceptance. These couplings are nearly absent when the decelerator operates such that only every third electric field stage is used for deceleration, while extra transverse focusing is provided by the intermediate stages. For many applications, the acceptance of a Stark decelerator in this so-called $s=3$ mode significantly exceeds that of a decelerator in the conventionally used ($s=1$) mode. This has been experimentally verified by passing a beam of OH radicals through a 2.6 meter long Stark decelerator. The experiments are in quantitative agreement with the results of trajectory calculations, and can qualitatively be explained with a simple model for the 6D acceptance. These results imply that the 6D acceptance of a Stark decelerator in the $s=3$ mode of operation approaches the optimum value, i.e. the value that is obtained when any couplings are neglected.
The interaction between PTCDA (3,4,9,10-perylene-tetracarboxylic-dianhydride) and rare gas or para-hydrogen samples is studied by means of laser-induced fluorescence excitation spectroscopy. The comparison between spectra of PTCDA embedded in a neon matrix and spectra attached to large neon clusters shows that these large organic molecules reside on the surface of the clusters when doped by the pick-up technique. PTCDA molecules can adopt different conformations when attached to argon, neon and para-hydrogen clusters which implies that the surface of such clusters has a well-defined structure and has not liquid or fluxional properties. Moreover, a precise analysis of the doping process of these clusters reveals that the mobility of large molecules on the cluster surface is quenched, preventing agglomeration and complex formation.
The dynamics of an x-ray-ionized two-component core-shell nanosystem is probed using doped helium (He) nanodroplets. First, a soft x-ray pump pulse selectively inner-shell ionizes the core cluster formed of heavier rare-gas atoms, causing electron migration from the He shell to the highly charged core. This ignites a He nanoplasma which is then driven by an intense near-infrared probe pulse. The ultrafast charge redistribution, evidenced by the rise of He$^+$ and He$^{2+}$ ion yields from the nanoplasma within $<70$ fs, leads to strong damping of the core cluster expansion. Thus, He droplets act as efficient tampers that reduce the radiation damage of embedded nanostructures, a property that could be exploited for improving coherent diffraction images.
The interaction between PTCDA (3,4,9,10-perylene-tetracarboxylic-dianhydride) molecules and solid rare gas samples is studied by means of fluorescence emission spectroscopy. On the one hand, laser-excited PTCDA-doped large argon, neon and para-hydrogen clusters in comparison with PTCDA embedded in helium nanodroplets are spectroscopically characterized with respect to line broadening and shifting. A fast non-radiative relaxation is observed before a radiative decay in the electronic ground state takes place. On the other hand, fluorescence emission studies of PTCDA embedded in bulk neon and argon matrices results in much more complex spectral signatures characterized by a splitting of the different emission lines. These can be assigned to the appearance of site isomers of the surrounding matrix lattice structure.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
