Abstract
Objectives
The main goal of this work has been to obtain the Renner-Teller (RT) coupled-channel (CC) dynamics of the reaction, NH(a1Δ) + D(2S), considering the four following channels: NH(a1Δ) + D(2S)--> N(2D) + HD(1Σg+) (depletion) (1)

NH(a1Δ) + D(2S) --> ND (a1Δ) + H(2S) (exchange) (2)

NH(a1Δ) + D(2S) --> NH(X3Σ-) + D(2S) (quenching) (3)

NH(a1Δ) + D(2S) --> ND(X3Σ-) + D(2S) (exchange+quenching) (4)

We have used the best available potential energy surfaces and have obtained initial-state-resolved probabilities, cross sections, rate constants and branching ratios via the time dependent real wave-packet method(1) (TDRWP) and flux analysis.

The two electronic states of NHD (X2B1 and A2A1) are the degenerate components of a linear 2Π state, thus giving rise to Renner-Teller(2) (RT) rovibronic nonadiabatic interactions allowing to change the electronic state. The RT effect is responsible to exchange and exchange + quenching reactions, so these reactions are not allowed under the Born-Oppenheimer approximation. Thus, the propagation of the RWP starts in the A2A1 excited potential energy surface(3) (PES), and when it reaches the H-N-D collinear arrangements it becomes possible to change the electronic state (jump into the X2B1 PES(3)) through the RT effect. Moreover, the NH2 X2B1 state has a deep minimum that traps the RWP for long time, increasing in this way the probability of nonadiabatic electronic transition (change of the electronic state).

Finally, the part of the RWP corresponding to reaction channels (1), (2), (3) and (4) is determined and the probability of each one of them is calculated, as a function of the initial conditions.

All the work detailed here is just the continuation of our previous project concerning the Renner-Teller dynamic and kinetic of atom+diatom reactions(5),(6).

References

(1) S. K. Gray and G. G. Balint-Kurti, J. Chem. Phys. 108, 950 (1998)

(2) C. Petrongolo, J. Chem. Phys. 89, 1297 (1988)

(3) Z.-W. Qu, H. Zhu, R. Schinke, L. Adam, and W. Hack, J. Chem. Phys. 122, 204313 (2005)

(4) S. Akpinar, P. Defazio, P. Gamallo and C. Petrongolo, J. Chem. Phys. 129, 174307 (2008)

(5) P. Gamallo and P. Defazio, J. Chem. Phys. 131, 44320 (2009)

(6) P. Defazio, P. Gamallo, M. González, S. Akpinar, B. Bussery-Honvault, P. Honvault and C. Petrongolo, J. Chem. Phys. 132, 104306-1 (2010)

Achievements
The first thing we had to do was to test our parallel code in the CINECA machines. Some problems arise from this first step due to poor flexibility of IBM compiler included in the CINECA sp6 machine. Several test were performed and a lot of cpu time was wasted with the aim of solving the problem. Thus, we checked the code running some jobs and comparing the results with others obtained using other computers. The success of this step allowed us to begin the dynamic study of the reactions indicated in the previous section.We want to thank CINECA responsible to allow us to increase the cpu time for finishing all the work expected in the project. Later on, we checked the convergence of the RT-CC-RWP (NH(a1Δ)+D(2S)) calculations verifying a large number of numerical parameters (e.g., rotational basis, mesh, number of iterations, etc.). Once the results were well converged, we performed the RWPs propagations for the title reaction. The different initial conditions investigated have been the following: NH (v0=0, j0=2,3,4) and J=0,1,2,…,40, and K0=0,1,…,min(j,J). Because the CC method has been used, the RWP has been propagated so many times as given by the number of possible K final values (J+1), using a single processor for each propagation. A total of 80000 iteration steps are required to reach convergence and due to this the propagations of the RWPs have been very time demanding. At present, we are carrying the analysis of all this amount of data using the flux and the asymptotic methods to obtain the probability of the four reaction channels. These probabilities will be the basis to obtain both the cross section and the rate constants for all processes. These rate constants will be compared with the experimental data available in the literature.