Radhakrishnan, R; Dr. Ramesh Babu, T(Cochin University of Science and Technology, July , 2008)
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Abstract:
In the present thesis we have formulated the Dalgarno-Lewis procedure
for two-and three-photon processes and an elegant alternate expressions
are derived. Starting from a brief review on various multiphoton processes
we have discussed the difficulties coming in the perturbative treatment
of multiphoton processes. A small discussion on various available methods
for studying multiphoton processes are presented in chapter 2. These
theoretical treatments mainly concentrate on the evaluation of the higher
order matrix elements coming in the perturbation theory. In chapter 3 we
have described the use of Dalgarno-Lewis procedure and its implimentation on second order matrix elements. The analytical expressions for twophoton
transition amplitude, two-photon ionization cross section, dipole
dynamic polarizability and Kramers-Heiseberg are obtained in a unified
manner. Fourth chapter is an extension of the implicit summation technique
presented in chapter 3. We have clearly mentioned the advantage of
our method, especially the analytical continuation of the relevant expressions
suited for various values of radiation frequency which is also used for
efficient numerical analysis.
A possible extension of the work is to study various multiphoton processcs
from the stark shifted first excited states of hydrogen atom. We
can also extend this procedure for studying multiphoton processes in alkali
atoms as well as Rydberg atoms. Also, instead of going for analytical expressions,
one can try a complete numerical evaluation of the higher order
matrix elements using this procedure.
Description:
Department of Physics,
Cochin University of Science and Technology