Question

Is it possible that there is no dipole moment change but polarizability change?

Answer 1

hello mate ⚘

dipole moment is a separation of positive and negative charges. when this separation changes during the vibrational motion of a molecule it is IR active. if there is no permanent dipole moment, there is no IR activity (e.g. N2, O2, H2).

polarizability is the relative tendency of a charge distribution, like the electron cloud of a molecule, to be distorted from its normal shape by an external electric field, like the one in an electromagnetic wave. if the polarizability changes during the vibrational motion of a molecule it is Raman active..