An absolute Raman instability in an inhomogeneous plasma

We examine stimulated Raman scattering in an inhomogeneous plasma, and demonstrate that there may be an exponentially growing decay, which owes its existence to reflexion of the electromagnetic decay wave. Unlike absolute instabilities, which depend on simultaneous vanishing of the wavenumber mismatch and its derivative, it can occur over a wide spectrum of decay wave frequencies, and may, therefore, be of greater practical importance than those instabilities.