More efficient compact fluorescent bulbs and other light sources could result from new ANU research which has accurately measured the lifespan of the longest-lived excitable atom for the first time.
A team from the Research School of Physics and Engineering has determined that excited helium atoms – which occur when the atoms are energised by a high velocity electron collision – remain excited for over 8,000 seconds or just over two hours.
“Excited atoms, which are also known as metastable atoms, are an important source of stored energy in ionized gases that occur in the Earth and planetary atmospheres, as well as in lighting and laser technologies,” explains physicist Professor Ken Baldwin.
“It’s this kind of ionized gas, or plasma, that’s inside the compact fluorescent light bulbs and other fluorescent lights around your house. It’s of fundamental interest to us to know exactly how long metastable atoms remain excited, but it also has implications for how we design better lighting systems in future.”
Professor Baldwin said that there has been just one earlier attempt by scientists to measure the duration of the helium atom’s excited state, and it had not been very accurate.
To rectify this, the ANU team used lasers to control and isolate a cloud of metastable helium atoms from their surrounding environment. The scientists were then able to measure the rate at which the atoms emitted ultraviolet photons to revert back to their normal, stable state.
“Such isolation is necessary in order to prevent collisions with other particles from destroying the excited state,” Professor Baldwin said. “By creating this experiment we were able to measure that the helium atoms remained excited for a little more than two hours (7,870+510 seconds), which is an eternity at the atomic scale where processes usually occur on micro- or nano-second timescales.
“Because the metastable helium atoms are so energetically excited and last for such a long period of time, this means that they are a very efficient source of stored energy in gas.”
The research finding is published in the journal Physical Review Letters.
Professor Baldwin said that the team’s finding is in excellent agreement with the predictions of the theory of quantum electrodynamics, which was established in the 1940s and is arguably the best-tested theory in modern physics.
For interviews: Professor Ken Baldwin 0432 987 251
Media assistance: Simon Couper, ANU media office 02 6125 4171, 0416 249 241
