Normal Modes of Ethylene

    In this exercise, animations of normal modes of ethylene can be examined.

To start an animation push the button START on the right frame. The operations can and should be performed with the animation on. Look for the IR active normal modes by studying their behaviour when the C2's are applied.

For this exercise you will need a character table. Label each of the normal modes. A "g" (gerade or symmetric) or a "u" (ungerade or antisymmetric) subscript can be added by inspection studying the symmetry properties of each vibrational mode with respect to inversion.
A good starting point is to work out (pen and paper work) the reducible representation spanned by the vibrational modes of ethylene and then express it in terms of the irreducible representations of D2h.

Check the choice of coordinates in the character table that you are using.( Because there are three mutually perpendicular C2 axes in D2h, the choice of x,y and z is arbitrary. A relabelling of this axes will lead to an interchange of the labels B1,B2 and B3).

Choose a normal mode: 1 2 3 4 5 6 7 8 9 10 11 12

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