STSM by Aurelie Chenel, Université Paris-Sud, Orsay (France), with Octavio Roncero Villa, Consejo Superior de Investigaciones Científicas (CSIC), Madrid (ES)
On February 24th, 2014 (26 days)
From FRANCE to SPAINLogo_Paris_Sud

Control of the infrared photodissociation of LiHF

We numerically study the competitive dissociation of the Van der Waals complex LiHF into the LiF + H or the Li + HF products. The potential energy surface of the LiHF system has been calculated by Roncero and al. (JCP 107,23 (1997)). Our goal aims at controlling the dissociation of LiHF toward the formation of the Li + HF products, that are not the products predominantly formed. The dynamics will be studied in hyperspherical coordinates. For the control we will use the Local Control Theory (LCT) strategy with a time-dependent approach based on Møller-operators.

The program we want to use for the control is written in hyperspherical coordinates. Furthermore, to be feasible in terms of calculation costs, we achieve it in a reduced two-dimensional model, so that in fact we use polar coordinates. To get such polar coordinates, it is usual to start with the Jacobi coordinates (rjac , Rjac ), as shown in the figure, where the angle γ is set at a value of 73° .

stsm-ACHENJacobi coordinates

    We first started with these coordinates. However, studying the energy potential curves we got, we then saw that they were not appropriate to describe our problem in two dimensions : we cannot have a good description of both rearrangement channels, leading to the LiF + H or the Li + HF products. To describe well both dissociation products, we are going to use bond coordinates, where r = rHF and R = rLiF . However, with these coordinates, we have to make some assumptions to be able to use our program for the control: in particular, we will neglect the cross-terms of the kinetic energy. These assumptions may be too strong, so that we will still have to think if these coordinates are suitable for the control.


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