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Separation of quadratic and linear external field effects in high J quantum beats

Summary: Separation of quadratic and linear external field effects
in high J quantum beats
M. Auzinshand R. Ferber
Department of Physics, University of Latvia, 19 Rainis Blvd, Riga LV-1586, Latvia
A. V. Stolyarov
Department of Chemistry, Moscow M. Lomonosov State University Moscow, 119899, Russia
(Received 21 March 1994; accepted 22 June 1994)
We discuss quantum beats in electronically excited molecular states with high rotational angular
momenta J appearing in time resolved fluorescence in conditions of quadratic and linear energy shift
dependence on magnetic quantum number M and external field strength. Density matrix formalism
is used to obtain in explicit form the expressions for time dependent fluorescence intensity after
&function pulsed excitation. In case of pure quadratic Stark effect, which is typical for `2 state
diatomics, excited state quantum beats for .B 1 exhibit a regular, or "grill" structure, consisting of
narrow equidistant "principal" peaks with equal relative amplitudes on the exponential decay
background. At linear polarized excitation the time intervals between the adjacent peaks are 27r/ozu,
wzObeing the splitting frequency between coherently excited M-sublevels with M = 2 and M' = 0.
If an admixture of linear contribution is present in field induced level shifts, the grill structure is
superimposed by a single frequency harmonic modulation. A special geometry was found in which
the quadratic beats are fully absent and the modulated grill pattern is brought into existence only by
the influence of linear term. Such a case takes place when the light polarization vector in


Source: Auzinsh, Marcis - Department of Physics, University of Latvia


Collections: Physics