The frequency of light required to create molecular vibration depends on the specific molecule and its vibrational modes. When light interacts with a molecule, it can be absorbed if its energy matches the energy difference between the molecule's ground state and an excited vibrational state.
The energy of a vibrational mode is quantized, meaning it can only have certain discrete values. The frequency of light required to induce molecular vibration is directly related to the energy difference between these vibrational states. This energy difference is determined by the molecular structure and the strength of the bonds within the molecule.
In general, the frequencies of light that commonly induce molecular vibrations are in the infrared (IR) region of the electromagnetic spectrum. This is because molecular vibrations typically involve relatively small changes in the potential energy of the atoms within a molecule, corresponding to energy levels within the IR range.
Different vibrational modes within a molecule can have different characteristic frequencies. For example, stretching vibrations, where the bond length increases and decreases, generally require higher frequencies than bending vibrations, where the bond angle changes.
It's important to note that the specific frequencies required for molecular vibration can vary widely depending on the molecule. Experimental techniques such as infrared spectroscopy are commonly used to study and identify the vibrational modes of molecules by analyzing the frequencies of light they absorb.