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تسجيل مستخدم جديدMeasurement of excited-state transitions in cold calcium atoms by direct femtosecond frequency-comb spectroscopy
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We apply direct frequency-comb spectroscopy, in combination with precision cw spectroscopy, to measure the ${rm 4s4p} ^3P_1 to {rm 4s5s} ^3S_1$ transition frequency in cold calcium atoms. A 657 nm ultrastable cw laser was used to excite atoms on the narrow ($gamma sim 400$ Hz) ${rm 4s^2} ^1S_0 to {rm 4s4p} ^3P_1$ clock transition, and the direct output of the frequency comb was used to excite those atoms from the ${rm 4s4p} ^3P_1$ state to the ${rm 4s5s} ^3S_1$ state. The resonance of this second stage was detected by observing a decrease in population of the ground state as a result of atoms being optically pumped to the metastable ${rm 4s4p} ^3P_{0,2}$ states. The ${rm 4s4p} ^3P_1 to {rm 4s5s} ^3S_1$ transition frequency is measured to be $ u = 489 544 285 713(56)$ kHz; which is an improvement by almost four orders of magnitude over the previously measured value. In addition, we demonstrate spectroscopy on magnetically trapped atoms in the ${rm 4s4p} ^3P_2$ state.
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