The absorption in the visible spectrum is due mainly to the harmonic v1 + 3v3 = 14,318 cm−1, which is equivalent to a wavelength of 698 nm. In liquid state at 20°C these vibrations are red-shifted due to hydrogen bonding, resulting in red absorption at 740 nm, other harmonics such as v1 +v2 + 3v3 giving red absorption at 660 nm.[1] The absorption curve for heavy water (D2O) is of a similar shape, but is shifted further towards the infrared end of the spectrum, because the vibrational transitions have a lower energy. For this reason, heavy water does not absorb red light and thus large bodies of D2O would lack the characteristic blue colour of the more commonly-found light water (1H2O).[4]