The timehyphen;dependent coupled cluster method is developed to provide a formally exact theory of quantumhyphen;mechanical motion of a vacuum state on multidimensional anharmonic surfaces with a view to calculate the molecular absorption spectra. The exact time evolution operator is represented as an exponential of creation operators. Since the separability requirments of manyhyphen;particle systems are built into such an ansatz, it is possible to develop approximations which can take into account any number of modes with much less computational effort than in a calculation by basishyphen;set expansion. The method gives a closed set of equations for harmonic surfaces and finite ordered equations for anharmonic surfaces when truncated at some finite rank.
展开▼
