Adiabatic Internal Force Constant, Mass, and Frequency

DEFINITION OF ADIABATIC INTERNAL FORCE CONSTANT, MASS, AND FREQUENCY 

Once vector Vn that determines the movement of the molecule under the influence of parameter qn is known, one can define a force constant, that corresponds to such a motion, by inserting (30) into the expression for the potential energy of the molecule in the harmonic approximation  

It has been shown [18] that defining an internal mass Mn associated with the internal vibration Vn by 

Therefore, one has to proceed in a different way to find a typical mass mn that opposes any change in the internal parameter qn- In this connection, two conditions should be fulfilled. First, the mass mn should be extractable from the functional form of the internal coordinate qn- Secondly, mn should be directly connected to the vibrational motion Vn caused by a change in qn- 

To fulfil these two conditions, one has to ask how the atoms of the molecule have to move so that the kinetic energy adopts a minimum and the generalized 

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