- News Home
5 December 2013 11:26 am ,
Vol. 342 ,
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
- 5 December 2013 11:26 am , Vol. 342 , #6163
- About Us
Transmuting Light Into X-rays
29 May 1998 7:00 pm
Despite advances in laser technology, one dream remains elusive: a table-top instrument that can pump out a beam of high-intensity, coherent x-rays. Such a device would give researchers Superman-like eyes to peer into living cells or catch glimpses of molecules during a chemical reaction. Now researchers have the beginnings of such a tool. A report in today's Science describes a trick for boosting visible laser light efficiently into the soft x-ray range.
When a laser plows into gas, it can occasionally rip an electron away from an atom before slamming it back into orbit. This violent reassembly produces a photon that can pack several hundred times the energy of an ordinary photon in the beam. This harmonic conversion, as it's called, can generate photons in the x-ray range. But the process is horribly inefficient because the gas slows down the laser light much more than it does the x-rays. The waves of x-rays emerge out of synch with each other and "tend to cancel each other out," says University of Michigan physicist Margaret Murnane.
Murnane and colleagues found a way to equalize the speed of the laser light and the x-rays in the gas. First they put argon in a precisely machined glass tube that speeds up the laser light but doesn't disturb the x-rays, which pass right down the center. Then the team adjusted the pressure of the gas, which fine-tunes the velocity of the two beams, until they marched along at the same pace.
To test their device, the team blasted the gas with light from a titanium-doped sapphire laser. At a "magic pressure of 30 torr," says physicist Andrew Rundquist, x-rays shot out of the 3-centimeter-long tube with a surprisingly high intensity. "At two o'clock in the morning I was yelling and screaming in the lab," he recalls. Roughly one in 100,000 photons made the jump to x-rays, at least 100 times the proportion seen without the glass tube, he says.
"This will be a wonderful new tool," says Ken Kulander, a physicist at Lawrence Livermore National Laboratory in California, who hopes to use it to zap molecules and watch how they fall apart. But Christian Spielmann, a physicist at the University of California, San Diego, says the x-rays aren't yet at a high enough energy to cut through water and see into cells. "This is a first step, but there are many more steps to go," he says.