Laser fluorescence spectroscopy has been performed on the two-photon 62S½ to 52D⅔ transition in Ba+. Using signals from an individual laser-cooled ion in a rf trap, a laser limited linewidth of less than 3 MHz has been achieved with an effective wavelength of 2.07 μm. The absence of any sidebands in the spectra spaced at the 5.5-MHz oscillation frequency of the ion in the rf quadrupole trap indicates that the ion vibrational motion must be well into the Lamb-Dicke regime. An upper limit of 165 nm is given to the vibrational amplitude.
© 1985 Optical Society of America
G. Janik, W. Nagourney, and H. Dehmelt, "Doppler-free optical spectroscopy on the Ba+ mono-ion oscillator," J. Opt. Soc. Am. B 2, 1251-1257 (1985)