Study of He*/Ne*+Ar, Kr, N, H, D Chemi-Ionization Reactions by Electron Velocity-Map Imaging.

The chemi-ionization of Ar, Kr, N, H, and D by Ne(P) and of Ar, Kr, and N by He(S) 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.

Sub-Kelvin Stereodynamics of the Ne(^{3}P_{2})+N_{2} Reaction.

We present an experimental study of the low-energy stereodynamics of the Ne(^{3}P_{2})+N_{2} reaction. Supersonic expansions of the two reactants are superposed in a merged beam experiment, where individual velocity control of the two beams allows us to reach average relative velocities of zero, yielding minimum collision energies around 60 mK. We combine the merged beam technique with the orientation of the metastable neon atoms and measure the branching between two reaction channels, Penning ionization and associative ionization, as a function of neon orientation and collision energy, covering the range 0.

Energy and orientation independence of the channel branching in Ne* + ND chemi-ionisation.

Collisions of excited neon atoms with ammonia molecules can lead to two reaction processes, dissociative ionisation and Penning ionisation. Both processes result in the ionisation of the ammonia molecule and redistribution of the electronic energy into the internal ammonia ion rovibrational modes. We performed energy dependent, crossed-beam stereodynamics studies of the branching ratio between the two ionisation processes.

Quantum-state-controlled channel branching in cold Ne(P)+Ar chemi-ionization.

A prerequisite to gain a complete understanding of the most basic aspects of chemical reactions is the ability to perform experiments with complete control over the reactant degrees of freedom. By controlling these, details of a reaction mechanism can be investigated and ultimately manipulated. Here, we present a study of chemi-ionization-a fundamental energy-transfer reaction-under completely controlled conditions.

Stereodynamics of Ne(P) reacting with Ar, Kr, Xe, and N.

Stereodynamics experiments of Ne(P) reacting with Ar, Kr, Xe, and N 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(P) atoms which were then oriented in a rotatable magnetic field and crossed with a beam of Ar, Kr, Xe, or N. The ratio of associative to Penning ionization was recorded as a function of the magnetic field direction for collision energies between 320 cm and 500 cm.

Energy Dependent Stereodynamics of the Ne(^{3}P_{2})+Ar Reaction.

The stereodynamics of the Ne(^{3}P_{2})+Ar Penning and associative ionization reactions have been studied using a crossed molecular beam apparatus. The experiment uses a curved magnetic hexapole to polarize the Ne(^{3}P_{2}), which is then oriented with a shaped magnetic field in the region where it intersects with a beam of Ar(^{1}S). The ratios of Penning to associative ionization were recorded over a range of collision energies from 320 to 500  cm^{-1} and the data were used to obtain Ω state dependent reactivities for the two reaction channels.

Imaging quantum stereodynamics through Fraunhofer scattering of NO radicals with rare-gas atoms.

Stereodynamics describes how the vector properties of molecules, such as the directions in which they move and the axes about which they rotate, affect the probabilities (or cross-sections) of specific processes or transitions that occur on collision. The main aspects of stereodynamics in inelastic atom-molecule collisions can often be understood from classical considerations, in which the particles are represented by billiard-ball-like hard objects. In a quantum picture, however, the collision is described in terms of matter waves, which can also scatter into the region of the geometrical shadow of the object and reveal detailed information on the pure quantum-mechanical contribution to the stereodynamics.

Inelastic Scattering of NO by Kr: Rotational Polarization over a Rainbow.

We use molecular beams and ion imaging to determine quantum state resolved angular distributions of NO radicals after inelastic collision with Kr. We also determine both the sense and the plane of rotation (the rotational orientation and alignment, respectively) of the scattered NO. By full selection and then detection of the quantum parity of the NO molecule, our experiment is uniquely sensitive to quantum interference.