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., C₂H_4, CH₃OH, CH₃NO₂, CH₃CHOO.    The approach is based on the VSCF/VCI method, which is in principle “exact”.

Information about version 4.9 can be accessed at https://www.dropbox.com/sh/uv1q9g2g42i3owr/AAA1_GTMGwXgW8wEbD_ExXZ6a?dl=0