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9EFFECTS OF OPTICAL LATTICE FIELD ON RELAXATION RATES OF "CLOCK' TRANSITION LEVELS IN STRONTIUM
ATOM
A.I. Magunov
A.M. Prokhorov General Physics Institute of RAS, 11991 Moscow, Russia
Nowadays, optical atomic frequency standards with highest accuracy are developed in different directions. One of the candidate for a novel atomic clock is
9 1 3 87
based on the strongly forbidden "clock" transition 5s S0-o-5s5p P0 in cold Sr atoms localized in an optical lattice. An extremely long lifetime of the excited state 5s5p 3P0 provides high enough Q-value of the resonance. However, interaction of an atom with a laser field, that forms the lattice, produces additional transition frequency shifts and widths from the complex energy shifts of the ground and excited levels.
In this report the results of estimations are presented for "clock" line broadening at the "magic" lattice wavelength (^m«813.4 nm), which gives equal values for the main contribution to ac polarization energy shifts of both levels. With account of laser induced and spontaneous transitions the rotating wave approximation gives the induced correction to the decay rate of the clock level c in the form
■ / # ^ 1
A4 = IL
m
(2 L +1)-1 fcn L=, A,uc
+ 2 I
nL (M„L.c ®nL.c
(2 L + 1) yj fc nLj=ifc. n'LJ=1 AnLJ=1. cAnLJ=1. c
(1)
n>n'.L (tt>n ^ - On XO/L.c ~ ®m H Lc®n%,c
where IL is the intensity of the lattice laser with the frequency am. a is the fine structure constant. m is the electron mass. fnLJ is the oscillator strength for the transition c^nLJ. AnLJc is the rate of the spontaneous radiation decay nLJ^c. For the 87Sr atom (1) gives the following effective lifetimes for the "clock" levels <53Pq) = 175IL_1 s and <5%) = 360IL_1 s for IL in kW/cm2.
