Research Highlight

Smarter optical clocks

doi:10.1038/nindia.2009.352 Published online 20 December 2009

An Indo-Dutch team has provided new clues about a bunch of atomic ions that could yield future optical clocks to give more precise timing1.

Conventional atomic clocks based on microwave transition of cesium have fundamental limits. Their microwave frequency was high about 50 years ago. But optical frequencies are 100,000 times higher so they can slice time into much smaller intervals.

The researchers explored the realm of optical frequency by using three atomic ions — strontium, barium and radium. They studied various states of these ions using a method called relativistic coupled-cluster method and compared their Stark and black-body radiation shifts (atomic phenomenon) for optical frequency standards with available experimental data.

Optical clocks are also about 100 times more stable than typical cesium clocks and need only a few seconds to reach femtosecond (one millionth of a nanosecond) precision, compared to many hours for a microwave atomic clock.

The authors of this work are from: KVI, University of Groningen , Groningen, The Netherland; Non-accelerator Particle Physics Group, Indian Institute of Astrophysics, Bangalore and Raman Center for Atomic, Molecular and Optical Sciences, IACS, Kolkata, India.


  1. Sahoo, K. B. et al. Comparative studies of dipole polarizabilities in Sr+, Ba+, and Ra+ and their applications to optical clocks. Phys. Rev. A 80, 062506 (2009) | Article