# Reaction rate from added vibrational energy

1. Aug 7, 2014

### sparkle_pony

I have a molecule with a certain kinetic, vibrational, and rotational energy.

It absorbs a photon which excites a vibrational mode.

I want to find an equation that describes how the molecules reaction rate with another molecule might change given the added vibrational energy.

Is there a name for this type of equation? If I wanted to pick up a textbook to learn it what would the subject of that textbook be?

2. Aug 8, 2014

### Staff: Mentor

The only thing I can think of is the old, good Arrhenius equation - but it doesn't care about details, it just calls for the temperature (which reflects averaged energy of molecules, without differentiating between kinetic, rotational and vibrational).

Somehow I doubt you will find kind of equation you described.

3. Aug 10, 2014

### sparkle_pony

Temperature: Temp is the average kinetic energy of all energy modes (translational, vibrational, and rotational). I probably could find an equation for calculating the new temperature, after photon absorption, assuming that the energy was equipartitioned beforehand.

Activation Energy: Exciting a vibrational mode might make that bond easier to break. This may lower the activation energy.

Steric parameter: If a collision with another reaction precursor occurs along the axis of vibration (i.e. one of the molecular atoms "swings" or "pushes" into the other precursor, thus raising the "effective relative velocity" at the moment of collision) then I can imagine a greater pre-exponential term.

Any thoughts on what terms would change, or equations to describe their change?

Assume the collision (reaction) occurs before relaxation of the excited vibrational state by another means.