In the present doctoral thesis, the reactive scattering for H- + H2 and H+ + H2 and its isotopologues

were investigated using different methods to solve the equations describing classical

and quantum mechanics. The studies aimed at providing insights into elementary reactions,

and may even go beyond these to more complex chemical reactions. The main results in this

dissertation can be summarized as follows:

In Chapter 2 the equations solving problems in quasi-classical mechanics were described,

which led to the definition of energy dependent reaction probabilities

and

reaction cross sections.

The formalism for time-dependent methods for the investigation of scattering processes was

presented in Chapter 3. In this section we discussed how to use the time-dependent quantum

wavepacket method to study the A-BC system. The dependence of the reaction probabilities

on the total angular momenta J was calculated to obtain information about the

integral reactive cross section.

The potential energy surfaces (PESs) for H3+ and H3- were described in Chapter 4. For the

H3+ system, a cut through the potential energy surface (PES) in the asymptotic region was

presented. For the H3- system three available ab initio potential energy surfaces have been used

in the applications: a) Stärck and Meyer (SM-PES), b) Panda and Sathyamurthy (PS-PES),

and c) Ayouz et al. (AY-PES). The differences in the PESs were investigated.

In the beginning of Chapter 5 the H+ + H2(v=0-5, j=0) collision was investigated nonadiabatically.

By comparison of the reaction probabilities using adiabatic and non-adiabatic

representations of the potential energy surfaces, it was found that, at low collision energies,

the reaction preferentially occurs adiabatically, but at higher collision energies non-adiabatic

effects have to be taken into account.

Reaction probabilities and reaction cross sections for the collision H- with H2 and its isotopologues

using quasi-classical trajectories and quantum wavepackets were presented in the main

part of Chapter 5. It was found that, at low collision energies, the reaction probabilities

using SM-PES and AY-PES are very similar. The reaction probabilities based on the PS-PES

are lower than those based on the SM-PES and AY-PES. At lower collision energies the reaction

cross sections calculated with SM-PES are higher than those calculated with PS-PES.

The reaction cross sections investigated with quasi-classical trajectories are higher than those

calculated with quantum wavepackets (using the same potential).

The last section of Chapter 5 showed results for the collision of H- and D- with HD. The total

I

reaction probabilities, the reaction cross sections, and the product ratios were determined using

quasi-classical trajectories. One can learn from these calculations that for the H- + HD(v=0-1, j=0) reaction and low collision energies, the main product are H2 + D-. At high collision

energies, the product channel HD + H- is slightly dominant. For the collision of D- with HD

and low collision energies the product channel HD + D- is strongly favored, but in the high

collision energy range, the product channel D2 + H- dominates.