Magneto-optically trapped atoms enable the determination of lifetimes of metastable states and higher lying excited states like the $rm{5d^{2}~^{3}F_{2}}$ state in barium. The state is efficiently populated by driving strong transitions from metastab
le states within the cooling cycle of the barium MOT. The lifetime is inferred from the increase of MOT fluorescence after the transfer of up to $30,%$ of the trapped atoms to this state. The radiative decay of the $rm{5d^{2}~^{3}F_{2}}$ state cascades to the cooling cycle of the MOT with a probability of $96.0(7),%$ corresponding to a trap loss of $4.0(7),%$ and its lifetime is determined to $rm{160(10)~mu s}$. This is in good agreement with the theoretically calculated lifetime of $rm{190~mu s}$ [J. Phys. B, {bf 40}, 227 (2007)]. The determined loss of $4.0(7),%$ from the cooling cycle is compared with the theoretically calculated branching ratios. This measurement extends the efficacy of trapped atoms to measure lifetimes of higher, long-lived states and validate the atomic structure calculations of heavy multi-electron systems.
Transition frequencies were determined for transitions in Ra in an atomic beam and for reference lines in Te$_2$ molecules in a vapor cell. The absolute frequencies were calibrated against a GPS stabilized Rb-clock by means of an optical frequency co
mb. The 7s$^2,^1$S$_0$(F = 1/2)-7s7p$,^1$P$_1$(F = 3/2) transition in $^{225}$Ra was determined to be $621,042,124(2),$MHz. The measurements provide input for designing efficient and robust laser cooling of Ra atoms in preparation of a search for a permanent electric dipole moment in Ra isotopes.
We have calculated the s-wave scattering length of all the even isotopes of calcium (Ca) and barium (Ba), in order to investigate the prospect of Bose-Einstein condensation (BEC). For Ca we have used an accurate molecular potential based on detailed
spectroscopic data. Our calculations show that Ca does not provide other isotopes alternative to the recently Bose condensed 40Ca that suffers strong losses because of a very large scattering length. For Ba we show by using a model potential that the even isotopes cover a broad range of scattering lengths, opening the possibility of BEC for at least one of the isotopes.
