Precision measurement of the isotope shifts of Sr by a laser cooling of a small quantity of ions in an ion trap.

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The initial aim of this research was the measurement of the isotope shifts of Sr nuclei, but because of (1) These isotope shifts were recently measured by an European group by co-linear fast-beam laser spectroscopy, and (2) Necessary diode lasers covering 1.09 mum light for laser cooling were found to be unavailable, we turned toward the precision measurement of the hyperfine structure of ^<87>Sr^+ ^2S_<1/2> ground state. Thanks to the many improvements of the whole system including the isotope separator to mass-separate and inplant onto a Pt filament inside the trap, the S/N became 10 times better. As the result we got sharp spectrum lines corresponding to the 19 lines of hyperfine structure which was further split by the Zeeman effect due to a stray magnetic field, and could identify the so-called 0 - 0 line unambiguously. We got, after correction of the 2nd-order shift sue to the stray field and calibration by a Cs standard, as the magnetic hyperfine constant A of ^<87>Sr^+^2S_<1/2> A=-1,000,473,673* 11 Hz. This value is important for future study of hyperfine anomalies of Sr isotopes, and also will serve as one of the sub-standards of frequency.