KARACHI (DNA): Researchers at the Niels Bohr Institute have measured the lifetime of an extremely stable energy level of magnesium atoms with great precision.
Magnesium atoms are used in research with ultra-precise atomic clocks. The new measurements show a lifetime of 2050 seconds, which corresponds to approximately one half hour. This is the longest lifetime ever measured in a laboratory.
The results have been published in the scientific journal Physical Review Letters. The experiment consists of magnesium atoms which are captured using laser light in a so-called magneto-optical trap and cooled to near absolute zero, minus 273 degrees Celsius.
Then the atoms are energized with laser light, which causes the electrons to jump from their ground state into a higher energy level. This higher energy level is called an excited state, but this state is usually very unstable and normally decays within a few nanoseconds. However, some special states may live much longer, up to several seconds or more before they decay, and are therefore called metastable states.
“Some atoms are easy to manipulate, while others are more difficult to get to jump into an excited state and the harder it is to get them to jump, the longer they last. We have been working with the magnesium-24 isotope, which is the most common form of magnesium. This atom has a metastable state, which is very difficult to excite, but using a special technique we have been able to transfer the magnesium atoms to the metastable state and measure a lifetime for this state of 2050 seconds. This is an extremely long lifetime,” explains atomic physicist Philip G. Westergaard, who as part of the research group under the leadership of Jan W. Thomsen at the Niels Bohr Institute is working towards developing an atomic clock based on ultra-cold magnesium atoms.
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