<Li> principally C-H stretching with a little C-N stretching; Q = q + aq (a <<1) </Li> <Li> principally C-N stretching with a little C-H stretching; Q = bq + q (b <<1) </Li> <P> The coefficients a and b are found by performing a full normal coordinate analysis by means of the Wilson GF method . </P> <P> Perhaps surprisingly, molecular vibrations can be treated using Newtonian mechanics to calculate the correct vibration frequencies . The basic assumption is that each vibration can be treated as though it corresponds to a spring . In the harmonic approximation the spring obeys Hooke's law: the force required to extend the spring is proportional to the extension . The proportionality constant is known as a force constant, k . The anharmonic oscillator is considered elsewhere . </P>

The number of fundamental modes of vibration in h2o molecule are