text: To get a feeling for the probability that the vibration of molecule may be thermally excited,
  we inspect the Boltzmann factor , where ΔE is the excitation energy of the vibrational mode, k the Boltzmann constant and T the absolute temperature. At 298 K (25 °C), typical values for the Boltzmann factor β are:
  β = 0.089 for ΔE = 500 cm−1
  β = 0.008 for ΔE = 1000 cm−1
  β = 0.0007 for ΔE = 1500 cm−1.
  (The reciprocal centimeter is an energy unit that is commonly used in infrared spectroscopy;  1 cm−1 corresponds to ). When an excitation energy is 500 cm−1, then about 8.9 percent of the molecules are thermally excited at room temperature. To put this in perspective: the lowest excitation vibrational energy in water is the bending mode (about 1600 cm−1). Thus, at room temperature less than 0.07 percent of all the molecules of a given amount of water will vibrate faster than at absolute zero.
  As stated above, rotation hardly influences the molecular geometry. But, as a quantum mechanical motion, it is thermally excited at relatively (as compared to vibration) low temperatures. From a classical point of view it can be stated that at higher temperatures more molecules will rotate faster,