Asymmetric Stretching

What needs to be thought of when deciding if a bond is going to be infrared active?

1. What, if any, is the dipole moment of the molecule?
2. What happens to the partial dipole moments of the molecule and how does that effect the total dipole moment?

The carbon dioxide molecule has no initial dipole moment because the partial dipole moments cancel each other out. As the oxygens move toward and away from the carbon at different speeds, the overall dipole moment change is not zero. Therefore, this stretching action has the change in dipole moment necessary to register in an IR spectrum.