Three fundamental vibrational modes of water vapor. They are denoted v₁ and v₃ for the symmetric and asyimrietric stretchings, and v₂ for the symmetric bending. The arrows simulate me direct and reciprocal vibrational motions of the Ο and the two H atoms (adapted from Schroeder 2002). The Ο to Η bond length is nearly 0.1 nm and the H-O-H average angle is 104°. The a and b axes discussed in Sect. 3.1 intersect at the center of mass of the molecule. The energy of the three fundamental vibrational states v₁ ν₂, v₃ are 3657, 1595 tind 3756 cm⁻¹, respectively; the equivalent stale temperature and warelengths are 5262, 2294 and 5404 K (see also Fig. 2) and 2.73, 6.27 and 2.66 μm.