Measurements may help show if constants are changing

Apr 28, 2006

Physicists at JILA have performed the first-ever precision measurements using ultracold molecules, in work that may help solve a long-standing scientific mystery--whether so-called constants of nature have changed since the dawn of the universe.

The research, reported in the April 14 issue of Physical Review Letters, involved measuring two phenomena simultaneously--electron motion, and rotating and vibrating nuclei--in highly reactive molecules containing one oxygen atom and one hydrogen atom.

The researchers greatly improved the precision of these microwave frequency measurements by using electric fields to slow down the molecules, providing more time for interaction and analysis. JILA is a joint institute of the National Institute of Standards and Technology (NIST) and the University of Colorado at Boulder.

Compared to the previous record, set more than 30 years ago, the JILA team improved the precision of one frequency measurement 25-fold and another 10-fold. This was achieved by producing pulses of cold molecules at various speeds, hitting each group with a microwave pulse of a selected frequency, and then measuring how many molecules were in particular energy states. The apparatus and approach were similar to those used in the NIST-F1 cesium atomic fountain clock, the nation's primary time standard, raising the possibility of designing a clock that keeps time with molecules, instead of atoms.

The JILA team's ability to make two molecular measurements at once enables scientists to apply mathematical calculations to probe the evolution over time of fundamental natural properties such as the fine structure constant, which is widely used in research to represent the strength of electromagnetic interactions. Another research group at the National Radio Astronomy Observatory plans to make similar frequency measurements soon of the same molecules produced in distant galaxies, which are so far from Earth that they represent a window into ancient history.

By comparing precision values for the fine structure constant on Earth and in distant parts of the universe, scientists hope to determine whether this constant has changed over 10 billion years. Because the fine structure constant is used in so many fields of physics, these measurements are a way to test the consistency of existing theories. The JILA measurements could enable any change in the fine structure constant over time to be determined with a precision of one part per million.

Citation: E.R. Hudson, H.J. Lewandowski, B.C. Sawyer, and J.Ye. 2006. Cold molecule spectroscopy for constraining the evolution of the fine structure constant. Physical Review Letters. April 14 (Vol. 96, 143004).

Source: NIST

Explore further: Experiment with speeding ions verifies relativistic time dilation to new level of precision

add to favorites email to friend print save as pdf

Related Stories

Variables of nature

Sep 05, 2014

Within physics there are certain physical quantities that play a central role. These are things such as the mass of an electron, or the speed of light, or the universal constant of gravity. We aren't sure ...

Designing exascale computers

Jul 23, 2014

"Imagine a heart surgeon operating to repair a blocked coronary artery. Someday soon, the surgeon might run a detailed computer simulation of blood flowing through the patient's arteries, showing how millions ...

Quantum tech disappoints, but only because we don't get it

Jul 16, 2014

Over the next five years, the UK government will spend £270m on supporting research in "quantum technology". When budget announcements were made in 2013, provisions for offshore wind and shale gas extraction were received ...

Physicists propose molecular clock to expose new physics

Jul 16, 2014

(Phys.org) —A trio of researchers from Germany, Bulgaria and Russia has proposed the idea of using a molecular clock to determine if the electron-proton mass ratio changes over time. In their paper published ...

The quantum dance of oxygen

Jul 07, 2014

Under extremely high pressure conditions oxygen molecules group into quartets and give rise to a 'dance of their magnetic moments.' This, as observed in a new study carried out by SISSA in collaboration with ...

OCO-2 takes the A-Train to study Earth's atmosphere

Jul 04, 2014

(Phys.org) —Every day, above our planet, five Earth-observing satellites rush along like trains on the same "track," flying minutes, and sometimes seconds, behind one another. They carry more than 15 scientific ...

Recommended for you

How Paramecium protozoa claw their way to the top

10 hours ago

The ability to swim upwards – towards the sun and food supplies – is vital for many aquatic microorganisms. Exactly how they are able to differentiate between above and below in often murky waters is ...

User comments : 0