Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userStark deceleration of OH radicals in low-field-seeking and high-field-seeking quantum states
121
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The Stark deceleration of OH radicals in both low-field-seeking and high-field-seeking levels of the rovibronic ${}^2Pi_{3/2},v=0,J=3/2$ ground state is demonstrated using a single experimental setup. Applying alternating-gradient focusing, OH radicals in their low-field-seeking ${}^2Pi_{3/2},v=0,J=3/2,f$ state have been decelerated from 345 m/s to 239 m/s, removing 50 % of the kinetic energy using only 27 deceleration stages. The alternating-gradient decelerator allows to independently control longitudinal and transverse manipulation of the molecules. Optimized high-voltage switching sequences for the alternating-gradient deceleration are applied, in order to adjust the dynamic focusing strength in every deceleration stage to the changing velocity over the deceleration process. In addition we have also decelerated OH radicals in their high-field-seeking ${}^2Pi_{3/2},v=0,J=3/2,e$ state from 355 m/s to 316 m/s. For the states involved, a real crossing of hyperfine levels occurs at 640 V/cm, which is examined by varying a bias voltage applied to the electrodes.
rate research
Read More
We demonstrate the deceleration of heavy polar molecules in low-field seeking states by combining a cryogenic source and a travelling-wave Stark decelerator. The cryogenic source provides a high intensity beam with low speed and temperature, and the travelling-wave decelerator provides large deceleration forces and high phase-space acceptance. We prove these techniques using YbF molecules and find the experimental data to be in excellent agreement with numerical simulations. These methods extend the scope of Stark deceleration to a very wide range of molecules.
We report on the Stark deceleration of a pulsed molecular beam of NO radicals. Stark deceleration of this chemically important species has long been considered unfeasible due to its small electric dipole moment of 0.16 D. We prepared the NO radicals in the X 2{Pi}3/2, v=0, J=3/2 spin-orbit excited state from the X 2{Pi}1/2, v=0, J=1/2 ground state by Franck-Condon pumping via the A 2{Sigma}+ state. The larger effective dipole moment in the J=3/2 level of the X 2{Pi}3/2, v=0 state, in combination with a 316-stages-long Stark decelerator, allowed us to decelerate NO radicals from 315.0 m/s to 229.2 m/s, thus removing 47 % of their kinetic energy. The measured time-of-flight profiles of the NO radicals exiting the decelerator show good agreement with the outcome of numerical trajectory simulations.
Whereas atom-molecule collisions have been studied with complete quantum state resolution, interactions between two state-selected molecules have proven much harder to probe. Here, we report the measurement of state-resolved inelastic scattering cross sections for collisions between two open-shell molecules that are both prepared in a single quantum state. Stark-decelerated OH radicals were scattered with hexapole-focused NO radicals in a crossed beam configuration. Rotationally and spin-orbit inelastic scattering cross sections were measured on an absolute scale for collision energies between 70 and 300 cm$^{-1}$. These cross sections show fair agreement with quantum coupled-channels calculations using a set of coupled model potential energy surfaces based on ab initio calculations for the long-range non-adiabatic interactions and a simplistic short-range interaction. This comparison reveals the crucial role of electrostatic forces in complex molecular collision processes.
The structure and quantum state of the reactants have a profound impact on the kinetics and dynamics of chemical reactions. Over the past years, significant advances have been made in the control and manipulation of molecules with external electric and magnetic fields in molecular-beam experiments for investigations of their state-, structure- and energy-specific chemical reactivity. Whereas studies for neutrals have so far mainly focused on weak-field-seeking species, we report here progress towards investigating reactions of strong-field-seeking molecules by introducing a novel crossed-molecular-beam experiment featuring an electrostatic deflector. The new setup enables the characterisation of state- and geometry-specific effects in reactions under single-collision conditions. As a proof of principle, we present results on the chemi-ionisation reaction of metastable neon atoms with rotationally state-selected carbonyl sulfide (OCS) molecules and show that the branching ratio between the Penning and dissociative ionisation pathways strongly depends on the initial rotational state of OCS.
Scalar gluons -- or sgluons -- are color octet scalars without electroweak charges. They occur in supersymmetric models of Dirac gauginos as the scalar partners of the gluino and carry Standard-Model type R charge. This allows them to interact with ordinary matter and to be produced at the LHC, singly as well as in pairs. Sgluons dominantly decay into gluons, top pairs, and a top quark plus a light quark. A pair of sgluons decaying into like-sign tops would provide a striking signature at the LHC. In our discussion of this channel we especially focus on the proper treatment of QCD jets.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
