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A schemeto efficiently calculate ro-vibrational (J> 0)eigenstates within the framework of the multiconfigurational time-dependentHartree (MCTDH) approach is introduced. It employsa basis of MCTDH wave packets which is generated in the calculationof vibrational (J= 0) eigenstates via existing MCTDH-basediterative diagonalization approaches. The subsequent ro-vibrationalcalculations for total angular momenta J> 0 usedirect products of these wave packets and the Wigner rotation matrices.In this ro-vibrational basis, the Hamiltonian matrix can be computedand diagonalized with minor numerical effort for any value of J. Accurate ro-vibrational states are obtained if the numberof iterations in the J= 0 calculations and the basisset sizes in the MCTDH wave function representation are converged.Test calculations studying CH2D show that ro-vibrationaleigenstates for moderately large Jcan be convergedwithin wavenumber accuracy with the same MCTDH basis sets and onlyslightly increased iteration counts compared to purely vibrational(J= 0) calculations. If large J’s are considered or very high accuracies are required, thenumber of iterations required to obtain convergence increases significantly.Comparing the theoretical results with experimental data for the out-of-planebend, symmetric stretch, and antisymmetric stretch fundamentals, theaccuracy of the ab initio potential energy surface employed is investigated. [ABSTRACT FROM AUTHOR]

Motivated by recent photodetachment experiments studyingresonance structures in the transition-state region of the F + CH4→ HF + CH3reaction, the vibrational dynamicsof the precursor complex CH4·F–isinvestigated. Delocalized vibrational eigenstates of CH4·F–are computed in full dimensionality employingthe multiconfigurational time-dependent Hartree (MCTDH) approach anda recently developed iterative diagonalization approach for generalmultiwell systems. Different types of stereographic coordinates areused, and a corresponding general N-body kineticenergy operator is given. The calculated tunneling splittings of theground and the lower vibrational excited states of the CH4·F–complex do not significantly exceed 1cm–1. Comparing the converged MCTDH results forlocalized vibrational excitations with existing results obtained bynormal-mode-based (truncated) vibrational configuration interactioncalculations, significantly lower frequencies are found for excitationsin the intermolecular modes. [ABSTRACT FROM AUTHOR]