Precise gJ- and gI-factor measurements of Ba+ isotopes

Laser-microwave double and triple resonance experiments were performed on clouds of Ba + ions confined in a Penning ion trap to induce and detect electronic and nuclear spin flip transitions. Collisions with buffer gas molecules in the trap was used to reduce the lifetime of a long lived metastable state of the ions, in which population trapping might occur, and to cool the ions to the ambient temperature. Loss of ions from the trap by collisions were prevented by, coupling the magnetron and reduced cyclotron motions by an additional r.f. field at the sun frequency of the two motions. Electronic Zeeman transitions in 138 Ba + and 135 Ba + were observed at a full width of about 3 kHz at a transition frequency of 80 GHz. The uncertainty of the line center was 3 × 10 9 . From the magnetic field calibration by the cyclotron resonance of electrons stored in the same trap the g J -factor for both isotopes could be determined to 2 x 10 -8 . From radiofrequency induced Δm I = I transitions of 135 Ba + the nuclear g-factor could be determined 5 × 10 - 6 . Both measurements improve earlier results by about one order magnitude.