Optical atomic clocks with suppressed black body radiation shift
  We study a wide range of neutral atoms and ions suitable for ultra-precise atomic optical clocks with naturally suppressed black body radiation shift of clock transition frequency. Calculations show that scalar polarizabilities of clock states cancel each other for at least one order of magnitude for considered systems. Results for calculations of frequencies, quadrupole moments of the states, clock transition amplitudes and natural widths of upper clock states are presented. 
Alexander Kozlov, Vladimir Dzuba, Victor Flambaum
physics.atom-ph