MULTIMODE is a general code that obtains the ro-vibrational eigenvalues and eigenfunctions of the “Watson Hamilonian” using the n-mode representation of the potential.  It has been applied to many polyatomic molecules from triatomics, e.g.,  H2O, tetratomics, e.g., H2CO, HOCO, H2O2, pentatomics, e.g., CH4, and larger molecules, e.g., C2H4, CH3OH, CH3NO2, CH3CHOO.    The approach is based on the VSCF/VCI method, which is in principle “exact”.

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