PhD Defence, Brian Bak Jensen, NBI – Niels Bohr Institute - University of Copenhagen

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PhD Defence, Brian Bak Jensen, NBI

The concept of time and measurement of time plays a unique role in modern physics and technology. For example is the meter defined today as the distance light travels in vacuum in 1/299.792.148 seconds. Equally so does a lot of practical applications depend on precise measurement of time. It can here be mentioned the GPS system, Mobile communication and navigation in space. All of these are dependent on atomic clocks, that is clocks where the electron act as a precise pendulum.

At the Niels Bohr Institute we are working on a super precise atomic clock based on magnesium atoms. For example has magnesium some of the longest lived atomic states that connect the ground state with higher lying metastable states. With the help of frequency stabilized lasers, it has been made possible to measure the lifetime of some of the metastable states. For example has the first measurement of the lifetime of the 3P2 state been measured. The 3P2 state has a lifetime of 2000 seconds and is amongst the most long lived atomic states which makes it interesting for atomic clock purposes.

The frequency stabilization of the lasers to an atomic transition has made it possible not only to lock the lasers in frequency but also to determine atomic properties of magnesium atoms.