Radio-frequency and laser spectroscopy studies of low-lying states in SrI

Abstract

Precision hyperfine structure (hfs) measurements in the 5s4d1D2 metastable state of87Sr were performed using the laser radio-frequency double resonance method. The magnetic dipole and electric quadrupole interaction constants were found to bea=−5.5734(4) MHz andb=55.421(6) MHz. In addition high-resolution laser spectroscopy experiments were performed in the 5s4d1D2 ↔ 5s6p1P1 and 5s4d1D2 ↔ 5p4d1D2 transitions in SrI. The isotope shifts in the transitions and the hfs in the upper states were determined. Comparison of the experimental results with corresponding relativistic self-consistent-field (SCF) calculations shows that the states involved are very strongly perturbed. Therefore no reliable nuclear quadrupole moment for87Sr can be deduced from the data presented here without more detailed calculations. A relativistic SCF calculation of the electron density at the nucleus was used in combination with muonic values of the nuclear mean square radii to evaluate the field shifts. From the experimental isotope shifts the specific mass shifts in the two transitions can then be deduced. This shift was found to be particularly large in the transition 5s4d1D2 ↔ 5s6p1P1.