High-resolution microwave spectroscopy on trapped ion clouds

Observation of Pr+Ions in Paul Trap

“…Though the "effective temperature" of the ions in a Paul trap is very high (of the order of several thousand K, resulting from the characteristic oscillatory motion performed by the ions due to the rf electric field), which results in a large Doppler broadening of the optical transitions (of the order of several GHz), it is nevertheless possible to perform optical-spectroscopic measurements of the hyperfine structure or isotope shifts of the stored ion species in a Doppler-free manner with the use of pulsed or continuous twostep excitation method (as shown on the examples of Th+ [3][4][5] and Hf+ [6] ions). A step further towards high precision in the hyperfine structure measurements is achieved with the use of another twostep excitation method -double optical-rf resonance [7,8], where the second step excites directly the magnetic-dipole rf-transitions between the hyperfine levels of a certain electronic (517) state. here the first-order Doppler effect is absent since the wavelength of the rf transitions considered is larger than the geometrical dimensions of the trap, the second-order Doppler effect is negligible and the natural line width is extremely small -the resolution under these circumstances can reach the Hz or even the mHz region.…”

“…here the first-order Doppler effect is absent since the wavelength of the rf transitions considered is larger than the geometrical dimensions of the trap, the second-order Doppler effect is negligible and the natural line width is extremely small -the resolution under these circumstances can reach the Hz or even the mHz region. This method has successfully been applied in the case of Eu+ [7] and Pb+ [8] ions. Recently its application has been extended also to investigations of metastable levels (within the frame of a project supported by the Volkswagen Foundation [9,10]).…”