EGAS41 - Swansea University

41 st EGAS CP 145 Gdańsk 2009
Autler-Townes effect: linshape analysis and determination of
excited state lifetimes
A. Ekers 1 , N.N. Bezuglov 2 , K. Miculis 1 , T. Kirova 1 , K. Blushs 1 , M. Auzinsh 1 ,
R. Garcia-Fernandez 3 , O. Dulieu 4 , M. Aymar 4
1 Laser Centre, University of Latvia, LV-1002 Riga, Latvia
2 Faculty of Physics, St. Petersburg State University, 198904 St. Petersburg, Russia
3 Dept. of Physics, University of Mainz, D-55128 Mainz, Germany
4 Laboratoire Aime Cotton, CNRS, Campus d’Orsay, France
A detailed theoretical analysis of the formation of Autler-Townes doublets [1] in the
excitation spectra of molecules is presented. It assesses the validity and accuracy of
our recently proposed technique for the determination of lifetimes of excited molecular
states based on the measurement of peak ratios of Autler-Townes doublets [2]. Influence
of various factors, like inhomogeneous line broadening and limited interaction time of
molecules with the laser fields is analyzed. A ladder of three rovibronic levels (1, 2, and
3) of different electronic states is considered. Levels 2 and 3 are coupled by a strong
dressing laser field, while a weak probe laser field is scanned across the 1-2 transition.
Coupled density matrix equations have been solved numerically and by using the split
propagation technique [3]. The peak ratio in the excitation spectrum of level 3 is found
to be directly related to the lifetime ratio of levels 2 and 3, but this ratio is altered if the
interaction time of molecules with the laser fields is comparable to lifetimes of the excited
levels. Comparison of the calculations with the experimental spectra for the ladders
X 1 Σ + g (0, 7) → A1 Σ + u (10, 8) → 51 Σ + g (10, 9) and X1 Σ + g (0, 7) → A1 Σ + u (11, 8) → 61 Σ + g (10, 9)
in Na 2 show that the lifetimes of the 5 1 Σ + g and 6 1 Σ + g (see Fig. 1) states are 35 and 40 ns,
respectively. These should be compared to the corresponding theoretical values of 42 and
42 ns obtained form the molecular potential calculations.
level f fluorescence (au)
1,0 experiment
0,8
0,6
0,4
0,2
0,0
-0,2
-100 0 100
∆ P
, MHz
f =30ns
t f =35ns
t f =40ns
t f =60ns
Figure 1: Fluorescence from the 6 1 Σ + g (10,9) state as a function of probe laser detuning and
comparisson with the theoterical curves.
References
[1] S.H. Autler, C.H. Townes, Phys. Rev. 100, 703 (1955)
[2] R. Garcia-Fernandez et al., Phys. Rev. A 71, 023401 (2005)
[3] M.D. Fiet et al., J. Compt. Phys. 47, 412 (1982)
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