Theory
Consider a system are of localized, non-interacting absorbing centers. Based on the semi-classical radiation absorption theory within the electric dipole approximation, the electric vector of the circularly polarized waves propagates in the +z direction, where + and -denote to RCP light and LCP light respectively. In this system, ω = 2nν is the circular frequency, and Ii = n – ik is the complex refractive index. As the light travels, the attenuation of the beam is expressed as
- I(z) = I0exp(−2ωkz/c)
where k is the absorption coefficient of the medium in the z direction. Circular dichroism (CD) is then defined as Δk = k– – k+, and it follows the sign convention of natural optical activity. In the presence of the static, uniform external magnetic field, the Hamiltonian for the absorbing center takes the form Ĥ = Ĥ0 + Ĥ1 which is parallel to the direction of the propagation of the electric field k. Because the transition occur between the two eigenstates of Ĥ0, a and j, the absorption and the CD intensity are determined as follows:
Read more about this topic: Magnetic Circular Dichroism
Famous quotes containing the word theory:
“The theory seems to be that so long as a man is a failure he is one of Gods chillun, but that as soon as he has any luck he owes it to the Devil.”
—H.L. (Henry Lewis)
“Freud was a hero. He descended to the Underworld and met there stark terrors. He carried with him his theory as a Medusas head which turned these terrors to stone.”
—R.D. (Ronald David)