TITLE: The influence of a laser field on the spontaneous 2\,p-1\,s\, transition

ABSTRACT:

We will compare two calculations of  the spontaneous emission rates from  
the first excited Stark states (n=2) of a hydrogenlike atom in the presence
of a monochromatic electromagnetic field.
The framework is that of a nonrelativistic third order perturbation theory.
We adopt a hybrid description  which combines a quantal description of the
emission and a  classical description of interaction with the external field
limited to the exchange of two laser photons [emission (absorption) and
reabsorbtion (reemission)].

The main object to be evaluated is
\begin{equation}
\Pi_{ijk}^{m}(\Omega ',\Omega)=\langle 1\,s |P_{i}
G(\Omega ')P_{j}G(\Omega)P_{k}|2\,1\,m \rangle \;
\end{equation}
with \,\mid 1\,s>, \,\mid 21m> Coulomb energy eigenfunctions, \vec P the
momentum operator and G the Coulomb retarded Green's function.
From the six pairs of values (\Omega\,',\Omega) met in the
transition amplitude  four of them  correspond to a reduced  Green's functions,
\,G_{red}(E_1)\, or \,G_{red}(E_2)\, in one of the factors,  with E_1 and
E_2 the first two Bohr levels.


The first calculation  is based on analytic expressions derived by us for
the emission rates, using the second-order correction to the ground-state
wave function [1]. The second evaluation is entirely numerical and it is
based on the Dalgarno-Lewis technique.

The numerical results will illustrate the effect of the
external field on the lifetimes of the states.


[1] V. Florescu, A. Halasz, and M. Marinescu, Phys. Rev. A 47, 394 (1993).

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