A new method for calculating the rotational tunnelling splitting for three-dimensional rotors

Abstract

We present a recursion method for calculating the rotational part of the wave function and the rotational tunnelling splitting ω for three-dimensional rotors. This Pocket Recursion Method (PRM) is designed to include the case of splittings that are smaller than 10–2 μeV. The PRM combines two advantages: fast convergence and accuracy. Applications to the various (NX4)2SnCl6 model potentials are shown (X = H, D). For the Smith potential, the calculated isotope shift agrees well with the recent experimental results. Applications to other rotational tunnelling systems are straightforward.