i]; are the

wavevector of the scattered and the incident photon, and q the

wavevector of the acoustic phonon (Fig.

In the indirect PWE, one formulate

wavevector components of light to be eigenvalues for a given frequency.

It can be easily seen that the incident

wavevector [?

The

wavevector of the electromagnetic field can be tuned to that of the vibration, be it a phonon or the oscillating mode of a macroscopic object, enhancing selectivity and strength of the interaction.

Where k is the

wavevector of the wave, [omega] is its frequency, and A' is its amplitude.

The curve between normalized frequencies and Bloch

wavevector K (called dispersion curve) is shown in Fig.

This concurs with Schrodinger solutions showing a negative energy increase with barrier length, [DELTA]d, while the imaginary eigen-value of the

wavevector [kappa] is constant, independent of barrier length (the Hartman effect)).

However, the development of light-scattering and neutron-scattering techniques showed not only that such relaxation times could be measured with accurateness, but that they were dependent on the

wavevector in such a way that nonlocal effects should be taken into consideration.

i] = (w/c , k), w is the frequency, k is the

wavevector and [PHI] is called the eikonal.

The innovation with respect to standard geometric optics is in the replacement of s with a more general, complex eikonal function [psi] = s + i[phi], where the imaginary

wavevector is perpendicular to the group velocity.

rho]], which is the variable of integration, is the horizontal projection of the

wavevector of an elementary plane wave composing the dipole radiation.

which has a

wavevector, wavelength and angular frequency given by: