Analysis of the H + D₂reaction mechanism through consideration of the intrinsic reactant polarisation

Abstract

The effect of reactant polarisation on the dynamics of the title reaction at collision energies up to 1.6 eV is analysed in depth. The analysis takes advantage of two novel theoretical concepts: intrinsic reaction properties and stereodynamical portraits. Exact quantum methods are used to determine the polarisation moments that quantify the intrinsic reactant polarisation at various levels of detail, including or not product state and/or scattering angle resolution. The data is then examined with the aid of stereodynamical portraits, which facilitate the rationalisation of the stereochemical effects that are relevant for the reaction dynamics. This allows for detailed characterisations of the so-called direct and delayed reaction mechanisms.

Polarization of molecular angular momentum in the chemical reactions Li + HF and F + HD

“…24 In the present HF(v = 3, j = 2) case, the rapid oscillations in the multipole states are observed in the full range of the scattering angles suggesting interference with a metastable state living at least for a complete rotations. From the semiclassical point of view, this can be conveniently discussed in terms of nearside-farside interferences 97 between trajectories with positive and negative values of the classical deflection function. We note here that a change in sign of the classical deflection function produces a different orientations of the axis because of the change in sign of the vectorial product between k and k r leading to the oscillations in the multipole states (see Figure 6).…”

Atom-diatom scattering dynamics of spinning molecules

“…In recent studies, the theoretical groundwork for describing the stereodynamics of atom-diatom reactions distinguishes between the preparation of the reactant polarisation (referred to as the extrinsic polarisation) and the conversion of this initial state into the product polarisation (which is controlled by the so called intrinsic polarisation of the reaction). [1][2][3] Such quantities are typically represented in terms of the so called polarisation dependent differential cross-sections, [27][28][29][30][31][32] which allow a complete and concise mathematical description of the various vector correlations associated with the collision process, or in terms of the more intuitive stereodynamics portraits. 1,2 In this study, we show instead two-dimensional differential cross-sections which offer an alternative visualisation of the reaction dynamics of the rotational wavepackets.…”

“…[1][2][3] Such quantities are typically represented in terms of the so called polarisation dependent differential cross-sections, [27][28][29][30][31][32] which allow a complete and concise mathematical description of the various vector correlations associated with the collision process, or in terms of the more intuitive stereodynamics portraits. 1,2 In this study, we show instead two-dimensional differential cross-sections which offer an alternative visualisation of the reaction dynamics of the rotational wavepackets. The advantage of the two-dimensional differential cross sections is that they highlight the spatial distribution of product molecules arising from the reaction of a uni-directionally rotating wavepacket.…”

“…The study and control of reactive collision mechanisms as a function of reactant and product molecule polarisation has been the subject of extensive study in recent years. [1][2][3] A powerful method to control the rotational dynamics of molecules is to excite rotational wavepackets with moderately strong, non-resonant laser pulses (see, e.g., Ref. 4).…”

“…15 Another interesting aspect is how the sense of rotation of the reactant molecules influences the reaction dynamics. 2 This requires the preparation of the molecules in rotational states with a superposition of magnetic sub-levels. 16 Molecules can be prepared in rotational states with non-zero average angular momentum, i.e., with the preferred sense of rotation by sequences of linear polarised laser pulses with different polarisations.…”