Lifetime of metastable fluorine atoms.

Abstract. For laser collimation of neutral F atoms, a resonance transition cycle between the metastable and the upper excited states (3s [sup 4] p[sub 5/2] arrow left and right 3p [sup 4] D[sup 0] [sub 7/2]) can be used as a two-level closed system. We have determined the lifetime of the metastable state (3s [sup 4]P[sub 5/2]) in F atoms by measuring the decay curve of the fluorescence intensity as a function of distance from the plasma source. Combining the measured velocity of F radicals from the Doppler shift of the fluorescence peak, we have obtained the lifetime of the F metastable state as 3.7 +/- 0.5 mu s. With this short metastable lifetime of F radicals, the simple Doppler cooling method using spontaneous light force is not practical for laser collimation off radicals. Use of stimulated light force may be necessary to collimate F radical beams in a short distance. [ABSTRACT FROM AUTHOR]