Crossed molecular beam

In analytical chemistry, crossed molecular beam experiments involve two beams of atoms or molecules which are collided together to study the dynamics of the chemical reaction, and can detect individual reactive collisions. Technique In a crossed molecular beam apparatus, two collimated beams of gas-phase atoms or molecules, each dilute enough to ignore collisions within each beam, intersect in a vacuum chamber. The direction and velocity of the resulting product molecules are then measured, and are frequently coupled with mass spectrometric data. These data yield information about the partitioning of energy among translational, rotational, and vibrational modes of the product molecules. History The crossed molecular beam technique was developed by Dudley Herschbach and Yuan T. Lee, for which they were awarded the 1986 Nobel Prize in Chemistry. While the technique was demonstrated in 1953 by Taylor and Datz of Oak Ridge National Laboratory, Herschbach and Le

Stereodynamics of Ne(3P2) reacting with Ar, Kr, Xe, and N2

Sean Dennis Steven Gordon, Andreas Osterwalder, Silvia Tanteri, Junwen Zou

Stereodynamics experiments of Ne(3P2) reacting with Ar, Kr, Xe, and N2 leading to Penning and associative ionization have been performed in a crossed molecular beam apparatus. A curved magnetic hexapole was used to state-select and polarize Ne(3P2) atoms which were then oriented in a rotatable magnetic field and crossed with a beam of Ar, Kr, Xe, or N2. The ratio of associative to Penning ionization was recorded as a function of the magnetic field direction for collision energies between 320 cm−1 and 500 cm−1. Reactivities are obtained for individual states that differ only in Ω, the projection of the neon total angular momentum vector on the inter-particle axis. The results are rationalized on the basis of a model involving a long-range and a short-range reaction mechanism. Substantially lower probability for associative ionization was observed for N2, suggesting that predissociation plays a critical role in the overall reaction pathway.

2018

Study of He*/Ne*+Ar, Kr, N2, H2, D2 Chemi-Ionization Reactions by Electron Velocity-Map Imaging

Sean Dennis Steven Gordon, Andreas Osterwalder, Silvia Tanteri, Junwen Zou

The chemi-ionization of Ar, Kr, N2, H2, and D2 by Ne(3P2) and of Ar, Kr, and N2 by He(3S1) was studied by electron velocity map imaging (e-VMI) in a crossed molecular beam experiment. A curved magnetic hexapole was used to state-select the metastable species. Collision energies of 60 meV were obtained by individually controlling the beam velocities of both reactants. The chemi-ionization of atoms and molecules can proceed along different channels, among them Penning ionization and associative ionization. The evolution of the reaction is influenced by the internal redistribution of energy, which happens at the first reaction step that involves the emission of an electron. We designed and built an e-VMI spectrometer in order to investigate the electron kinetic energy distribution, which is related to the internal state distribution of the ionic reaction products. The analysis of the electron kinetic energy distributions allows an estimation of the ratio between the two-reaction channel Penning and associative ionization. In the molecular cases the vibrational or electronic excitation enhanced the conversion of internal energy into the translational energy of the forming ions, thus influencing the reaction outcome.

2021

Energy dependent stereodynamics of the Ne(3P2)+Ar reaction

Sean Dennis Steven Gordon, Justinas Jankunas, Andreas Osterwalder, Silvia Tanteri, Junwen Zou

The stereodynamics of the Ne(3P2)+Ar Penning and Associative ionization reactions have been studied using a crossed molecular beam apparatus. The experiment uses a curved magnetic hexapole to polarise the Ne(3P2) which is then oriented with a shaped magnetic field in the region where it intersects with a beam of Ar(1S). The ratios of Penning to associative ionization were recorded over a range of collision energies from 320 cm-1 to 500 cm-1 and the data was used to obtain

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state dependent reactivities for the two reaction channels. These reactivities were found to compare favourably to those predicted in the theoretical work of Brumer et al.

American Physical Society2017

Energy dependent stereodynamics of the Ne(3P2)+Ar reaction

Sean Dennis Steven Gordon, Justinas Jankunas, Andreas Osterwalder, Silvia Tanteri, Junwen Zou

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state dependent reactivities for the two reaction channels. These reactivities were found to compare favourably to those predicted in the theoretical work of Brumer et al.

American Physical Society2017

Stereodynamics of Ne(3P2) reacting with Ar, Kr, Xe, and N2

Study of He/Ne+Ar, Kr, N2, H2, D2 Chemi-Ionization Reactions by Electron Velocity-Map Imaging

Energy dependent stereodynamics of the Ne(3P2)+Ar reaction

Study of He/Ne+Ar, Kr, N2, H2, D2 Chemi-Ionization Reactions by Electron Velocity-Map Imaging

Energy dependent stereodynamics of the Ne(3P2)+Ar reaction

Stereodynamics of Ne(3P2) reacting with Ar, Kr, Xe, and N2