Measurement of product alignment in beam–gas chemiluminescent reactions

Abstract

A procedure is developed for determining the product rotational alignment in the center of mass frame from polarization measurements of the chemiluminescent atom-diatom exchange reaction A + BC-.AB* + C under beam-gas conditions. The degree of product alignment with respect to the initial relative velocity reaches a maximum when all reagent orbital angular momentum appears as product rotational angular momentum. For beam-gas chemiluminescence, this implies a limiting degree of polarization of the product emission referenced to the beam axis about which the initial relative velocities are cylindrically symmetric. Calculations are carried out to determine this limiting chemiluminescent polarization for a wide range of beam-gas reaction conditions. Averages over initial conditions are performed by Monte Carlo sampling. These calculations show that under realistic conditions the degree of beam-beam polarization does not exceed twice that of beam-gas polarization. Product polarization is measured in the beam-gas chemiluminescent reaction Ca('D) + HCI-.CaCI(B',.!' +) + H and found to be greater than 20%. Because of kinematic constraints, this value closely approaches the calculated limiting polarization. 2222

Reactive scattering of Na(3 2P3/2)+HCl

“…Unfortunately, in the present Na + Hel scattering experiments, there is no feature in the angular or velocity distributions which can be uniquely 8 assigned to ground state Na(3S) scattering. If such a feature can be found, its depletion by laser excitation of the Na atoms would measure the effective Na fraction optically pumped to the 32p3/2 state.…”

“…The contributions from the excited state at each laboratory angle, compared to those from ground state, are derived from the angular data by the equation (8) EXPERIMENTAL RESULTS…”

The Influence of Collision Energy on the Reaction H+HS→H2+S

“…The center-of-mass (CM) frame 15,17,21 is chosen to describe the vector correlation, and its details are specified as follows. As can be seen in Figure 1, k is the reactant relative velocity parallel to the z-axis, and k represents the product relative velocity.…”

“…[14][15][16][17][18][19][20][21][22][23] The vector properties such as orientation and alignment of the product molecules for the reaction A+BC→AB+C were investigated in detail, especially by Han et al. [18][19][20][21]23 Combined with scalar ones, the vector properties can help to reveal the details of the reaction with rich space information.…”

Coherence effects in the polarization of the light emitted by photofragments

“…In particular, the polarization of the fluorescence emitted by the fragments yields information concerning the alignment and orientation of the fragments, as well as on the nature of the photon absorption, the dynamics of the half-collision process, etc. This situation is not restricted to photodissociation experiments since similar examples are found in photoionization processes [2] as well as in chemiluminescence reactions [3].…”