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Atomic Clocks

3. How to Trap Atoms and Detect Atomic Transitions

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In this mini-lecture, we discuss how to hold, or trap, atoms and how to detect the transitions of atoms from lower to upper energy states. In particular, we consider: (i) physicists, Hans Dehmelt and Wolfgang Paul, who created the first atomic ion traps; (ii) the basic idea of how atomic ion traps work, which involves applying electric potentials to a set of electrodes in order to create a 3D harmonic well that traps the ion; (iii) the atomic ion trap for a mercury ion used to make an atomic clock, specifically discussing the ion’s transition between energy levels depending on the laser excitation wavelength; (iv) an image captured with a UV-sensitive camera that allows us to see an individual mercury ion; (v) how laser cooling can be used to suppress Einstein’s relativistic time dilation; and (vi) the NIST IONS research group in 1979.


In this course, Professor David Wineland (University of Oregon) discusses atomic clocks. In the first mini-lecutre, we compare traditional and modern methods of navigation, where we see that precision in a clock’s ‘tick rate’ is essential for modern satellites and GPS. In the second mini-lecture, we discuss how a basic, mechanical clock (such as a pendulum clock) works, compare these clocks with atomic clocks, explain how to make an atomic clock with lasers/masers, and discuss why atomic clocks are so accurate and reliable. In the third mini-lecture, we introduce the concept of holding, or trapping, a single atom (or ion) and how this can be used to detect atomic transitions between the energy levels of the atom. The fourth mini-lecture discuses further effects on atomic clocks, notably gravitational-potential redshifts, and notes future uses of atomic clocks.


Professor David Wineland is the Philip H. Knight Distinguished Research Chair and Research Professor in the Department of Physics at the University of Oregon and was jointly awarded the 2012 Nobel Prize in Physics for devising methods to study the quantum mechanical behaviour of individual ions. In 1975, he joined the National Institute of Standards and Technology (NIST) in Boulder, Colorado, where he started the ion storage group and was a professor adjoint at the University of Colorado at Boulder. Professor Wineland and his group at NIST were able to place an individual electrically trapped laser-cooled ion in a superposition of two different locations. This permitted them to experimentally study fundamental physics, such as quantum mechanical behavior. This work led Professor Wineland and his group to make advances in quantum computing and atomic clocks.

Cite this Lecture

APA style

Wineland, D. (2022, January 12). Atomic Clocks - How to Trap Atoms and Detect Atomic Transitions [Video]. MASSOLIT.

MLA style

Wineland, D. "Atomic Clocks – How to Trap Atoms and Detect Atomic Transitions." MASSOLIT, uploaded by MASSOLIT, 13 Jan 2022,

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