Quantum graph model for rovibrational states of protonated methane

We calculate the rovibrational states of the protonated methane molecular ion (CH+5) for angular momenta up to J = 4. Our novel approach is based on a quantum graph description of the low-energy nuclear dynamics. Previous work on the quantum graph model neglected rotational degrees of freedom and so only described purely vibrational excitations. We extend this work significantly to give the first example of a full rovibrational quantum graph model. We compare our results to 7D variational calculations, finding good agreement for J ≤ 3. To the best of our knowledge, the J = 4 results are the first of their kind.