First principles determination of the NH2/ND2((A)over-tilde,(X)over-tilde) branching ratios for photodissociation of NH3/ND3 via full-dimensional quantum dynamics based on a new quasi-diabatic representation of coupled ab initio potential energy surfaces

The A-band photodissociation of ammonia is an archetypical and long studied example of non-adiabatic dynamics in a polyatomic system. Due to a well-known conical intersection seam, electronically excited NH3 can produce either the ground ((X) over tilde B-2(1)) state or the excited ((A) over tilde (2)A(1)) state of the NH2 fragment. In this work, the non-adiabatic dynamics is investigated using a six-dimensional wave packet method and an improved version of a newly developed diabatic Hamiltonian based on high quality ab initio data. The (A) over tilde (2)A(1)/(X) over tilde B-2(1) branching ratios are in excellent agreement with experimental estimates, thus validating the non-adiabatically coupled Hamiltonian. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4753425]