Lowest eight vibrational s)ate_i of water vapor and their quantum numbers (υ₁,υ₂,υ₃). Stares of a₁ symmetry are referred to by horizontal blue lines, states of b₂ symmetry by aubergine lines. Vibration-rotation interactions are indicated by lines connecting the interacting states. The labels F, C and C’ symbolize Fermi, Coriolis, and rotational (or Coriolis-type) interactions. The energy of each vibrational band origin is given in Kelvin below each horizontal solid line. The rotational and ro-vibrational transitions in the range of snerau covered by the ATOMIUM project are listed in Table 2. Four examples, corresponding to lines 10, 14, 8 and 4 in Table 2, are shown with their quantum identification, in the form on dotted horizontal green lines; they are ordered by increasing energy.