Polarizers may enhance remote chemical detection

March 11, 2009

Chemists can analyze the composition of a suspected bomb -- without actually touching and possibly detonating it -- using a technique called laser-induced breakdown spectroscopy, or LIBS. The tool is also commonly used for "stand-off" detection in such harsh or potentially dangerous environments as blast furnaces, nuclear reactors and biohazard sites and on unmanned planetary probes like the Mars rovers.

Information provided by LIBS, however, is sometimes clouded by interfering signals caught by the -- and eliminating the background can be expensive. But a group of chemists at the University of Illinois at Chicago reports that equipping LIBS with a can do the job at a lower cost and probably with equal or greater sensitivity than the tools presently in use.

Robert Gordon, professor and head of chemistry at UIC, became interested in polarized light after reading books by cosmologist Brian Greene that described a slight polarization of the cosmic microwave background left over from the Big Bang. Out of curiosity, Gordon had his lab group zap a crystal of silicon by firing pairs of near-infrared laser pulses at 80 femtoseconds -- or 80 millionths of a billionth of a second. This "mini-Big Bang-like" caused a brief spark, or plasma, that gave off ultraviolet light, which the group checked for polarization.

"We thought we'd see maybe a few percent polarization," said Gordon. "But when we saw 100 percent, we were totally astonished."

The spectrum of light they studied, similar to the rainbow a prism creates when held up to sunlight, includes a series of lines that are the hidden signatures of chemical elements. To get rid of the background spectrum and focus just on the element lines, current LIBS use a time-resolved method that works like a by snapping at nanosecond speeds. Gordon's group discovered that by eliminating the shutter and instead using a rotating polarizer, they could filter out the background and focus on the lines.

"The polarizer costs just pennies, whereas a time-shutter is a very expensive component," Gordon said. "By simply putting a polarizer in a detector and rotating it to get maximum signal-to-noise ratio, you can improve the quality of the signal effortlessly and fairly cheaply."

Gordon said there is still basic work that needs to be done to answer why the light gets polarized. He said that varying the angle and the intensity of the laser pulses used to ablate the sample material may provide additional ways to enhance LIBS.

More information: Gordon and his coworkers first reported their findings in the Feb. 15 issue of Optics Letters and will present their results at the Conference on Lasers and Electro-Optics May 31-June 5 in Baltimore.

Source: University of Illinois at Chicago (news : web)

Explore further: Hewlett Packard to create 500 jobs in Ireland

Related Stories

Hewlett Packard to create 500 jobs in Ireland

March 10, 2009

US technology company Hewlett Packard is to create 500 jobs with an 18-million-euro (23-million-dollar) expansion of its global service desk operation in Leixlip, County Kildare southwest of Dublin, Prime Minister Brian Cowen ...

US struggles to pinpoint cyber attacks: Top official

March 10, 2009

The United States often cannot quickly or reliably trace a cyber attack back to its source, even as rival nations and extremists may be looking to wage virtual war, a top official warned Tuesday.

The changing roles of mothers and fathers

March 10, 2009

Elvire Vaucher is a professor at the Université de Montréal School of Optometry. Her husband is an artist who works from home. Upon the birth of their second child in 2003, she took only three months maternity ...

Recommended for you

A new form of real gold, almost as light as air

November 25, 2015

Researchers at ETH Zurich have created a new type of foam made of real gold. It is the lightest form ever produced of the precious metal: a thousand times lighter than its conventional form and yet it is nearly impossible ...

New 'self-healing' gel makes electronics more flexible

November 25, 2015

Researchers in the Cockrell School of Engineering at The University of Texas at Austin have developed a first-of-its-kind self-healing gel that repairs and connects electronic circuits, creating opportunities to advance the ...

Getting under the skin of a medieval mystery

November 23, 2015

A simple PVC eraser has helped an international team of scientists led by bioarchaeologists at the University of York to resolve the mystery surrounding the tissue-thin parchment used by medieval scribes to produce the first ...

Atom-sized craters make a catalyst much more active

November 24, 2015

Bombarding and stretching an important industrial catalyst opens up tiny holes on its surface where atoms can attach and react, greatly increasing its activity as a promoter of chemical reactions, according to a study by ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.