What do the “Siamese squid,” the “double Hubble,” the “blinking planetary” and the “Saturn nebula” have in common?

All are distant, dying stars, whose images have been captured by the Hubble Space Telescope. And all will be described this Wednesday by 91探花 astronomy professor Bruce Balick, who, with his colleagues has captured some of the most remarkable portraits yet seen through the lens of the orbiting telescope.

In a press conference at NASA in Washington D.C. on Wednesday (10 p.m. PST), Balick will describe spectacular images that provide insights into the final stages of stellar evolution, as well as a glimpse into the distant final days of the solar system. Four of the seven new images being released were taken by Balick and his colleagues.

The photographs show the material ejected by geriatric stars once similar to the Sun. One image, of M2-9, dubbed the “Siamese squid”, is a striking example of a planetary nebula shaped like a butterfly. Hubble 5 is a double-lobed nebula known as the “double bubble.” GGC 6826 has an eye-like appearance and is known as the “blinking planetary.” NGC 7009 has a bright central star at the center of a dark cavity bounded by a rim of dense blue and red gas. It is known as the “Saturn nebula.”

Balick notes that 95 percent of all the stars in our galaxy, the Milky Way, will become planetary nebulae, including the Sun. These dying bodies are formed when a red giant star ejects its outer layers as clouds of luminescent gas, revealing a dense white dwarf star at the core.

The researcher notes that the term “planetary nebulae” is a misnomer, since the objects are stars, not planets, and no planets are visible within them. Says Balick: “We might reasonably call the 10,000 galactic planetary nebulae flaring ornaments that adorn our galaxy, much like the twinkling lights on a Christmas tree.”

### Balick can be reached at 543-7683, or balick@astro.washington.edu
Following the press conference, Balick will be available for interviews between 1:10 and 2:30 p.m. PST over the NASA Select television network. Television stations wishing to interview Balick should contact Diana Corridon at Goddard Space Flight Center at (301) 286-0041.

Previews of the conference can be seen on the World Wide Web at or at

San Francisco — This might not help Americans breathe any more freely, but it seems they are not entirely to blame for the chemical smog that hangs over cities along the U.S. West Coast. A new study indicates that about 10 percent of the ozone and other pollutants are arriving from the industrialized nations of East Asia.

“Although Los Angeles can’t blame the bulk of its air problems on Asia, there is definitely some contribution,” says Dan Jaffe, associate professor of science, technology and the environment at the 91探花, Bothell. “Our results show that Asian pollution is affecting much of the U.S.West Coast, with Washington and Oregon affected slightly more because of wind patterns.”

Jaffe presented his findings at the fall meeting of the American Geophysical Union in San Francisco today (Wednesday, 8:30 a.m. PST). He is the principal investigator on a three-year project to measure pollutants in the atmosphere from the 91探花’s remote Cheeka Peak research station on the Olympic Peninsula.

Previously Jaffe had proved that wind-borne Asian pollutants can reach as far as Hawaii. His first data from a West Coast site, acquired last May, measured atmospheric levels of pollutants such as nitrogen oxide, carbon monoxide, ozone and hydrocarbons. His collaborator, Terje Berntsen of the University of Oslo, Norway, used these data in a computer model that employs meteorological observations to predict and calculate where and how pollutants move through the atmosphere on any particular day. By combining industry’s known emissions of pollutants with such factors as wind speeds and direction, the computer program indicated that 10 percent of the ozone and carbon monoxide detected at Cheeka Peak had blown across the Pacific Ocean from Asia.

Ozone, which can damage the human respiratory system and destroy vegetation, is the product of nitrogen oxides released from the burning of fossil fuels, and has a long atmospheric life. Carbon monoxide is released directly into the atmosphere from the combustion of fossil fuels. Both, says Jaffe, are atmospheric pollutants that probably would have been considerably lower in Asia just 30 years ago.

Berntsen’s computer model is a simulation of the global atmosphere. It divides the Earth into 24 boxes of latitude and 36 of longitude, all piled nine layers high. In every box, at every moment of time, data on pollutants being released into the atmosphere is fed into the program, including the types of chemicals and their specific reactions. To this is added NASA wind data. In the Pacific, winds generally travel from west to east.

Because wind patterns can vary greatly over the course of a year, researchers typically record intense pollution levels on one day and much lower levels on the next. The computer “smoothes out” this difference by calculating the pollution level in each grid box, similar to taking a snapshot of the globe. To calculate how much of this global pollution originated in Asia, the researchers blank out the boxes over industrialized East Asia, and run the computer program a second time. They then look at the difference in the two simulations.

This is Jaffe’s fourth project investigating the transportation of pollutants through the atmosphere. He has also made measurements on Oki Island off the Coast of Japan and on Shemya at the tip of the Aleutian Islands chain.

All the data analyzed in the computer model, he says, indicates an increasing flow of pollutants from industrialized Asia. “Despite the recent economic problems, Asia is booming, and the spread of its pollutants is rapidly increasing,” he says.

###
Jaffe is at (425) 352-5357, or djaffe@u.washington.edu
He can be reached through the AGU press room, (415) 905-1007
He is staying at the Juliana Hotel, (415) 392-2540

What was found by three graduate students — Kirsten Lorentzen of the 91探花 and Robin Millan and Jason Foat of the University of California at Berkeley — has scientists scrambling for an explanation: an intense stream of X-rays, occurring in seven bursts, each separated by only a few minutes and lasting for a total of half an hour. The evidence was clear that the high energy bursts came not from outer space, but from the Earth’s upper atmosphere.

“The source is simply not known,” says Lorentzen, who, with Millan, is presenting posters on the mystery at the fall meeting of the American Geophysical Union here (Dec. 10 at 8:30 a.m.). There are high-energy X-rays located in the magnetosphere, the intense magnetic field that surrounds the Earth, Lorentzen says. “But they don’t usually enter the Earth’s atmosphere, and certainly not in big bursts like this.”

Lorentzen, Millan and Foat made their discovery when they were taking part in an international campaign organized by the Universite Paul Sabatier, Toulouse, France, to study the aurora from stratospheric balloons in conjuction with scientific satellites passing overhead.

The aurora, also known as the northern lights, is a phenomenon visible more than 60 miles above the Earth in a region where electrons collide with atmospheric particles. The electrons come from near space around the Earth, and travel along the planet’s magnetic field lines. In addition to creating the aurora’s heavenly lights, the electrons also create a type of radiation known as bremsstrahlung, or X-rays. This radiation cannot penetrate the thickest layers of the Earth’s lower atmosphere, but can be observed from balloons at a height of about 20 miles.

Last year’s balloon observing mission carried several types of X-ray instruments, including an X-ray imaging camera built by Lorentzen at the 91探花and a germanium X-ray spectrometer built at UC Berkeley. The spectrometer measured the energy of the X-ray bursts, and the camera took X-ray images of the mysterious event.

What is new about this discovery, says Lorentzen, is that the X-rays were recorded during the day and there was no auroral activity overhead. Although high energy X-rays have been observed in astrophysics before, she says, this is the first time that X-rays of such intense energy — mega-electron-volts — have been detected emerging from around the Earth.

Lorentzen notes that it is known from satellite observations that high energy electrons become trapped in the Van Allen radiation belt surrounding the Earth, but it is not known how they could penetrate the planet’s atmosphere to produce the type of energy bursts recorded.

“This is a scientific mystery, a very difficult problem,” she says. “We don’t understand the mechanism that causes this type of event.”

### Lorentzen is at (206) 543-7251, or at kirsten@geophys.washington.edu
Her adviser on the project is Michael McCarthy, 91探花research associate professor of geophysics, at (206) 685-2543, or mccarthy@geophys.washington.edu
Lorentzen and Millan can be reached through the AGU press room, (415) 905-1007

The proposition that the Earth’s little understood inner core is a frozen yet white hot globe of curiously laid out iron crystals, spinning independently of the rest of the planet, has been given a boost by a 91探花 researcher.

But Kenneth Creager, an associate professor of geophysics, has also found that the inner core, which has a diameter three-quarters that of the moon, is not as agile as thought. Its rotation rate, relative to the Earth’s two outer layers, the crust and the mantle, is four to 12 times slower than previously estimated.

Creager’s latest findings on the behavior and structure of the most hidden and enigmatic part of the planet are being published in tomorrow’s (Nov. 14) edition of Science.

The new data, he says, is “clear confirmation” that the inner core is rotating at a faster rate than the rest of the planet. “But we have only a snapshot in time and cannot say how fast the inner core was spinning millions or even hundreds of years ago,” Creager says.

The inner core’s independent rotation is thought to be caused by a process called convection in the molten iron outer core that surrounds the inner core and that produces the Earth’s magnetic field. This process is driven in part by the energy transferred as the entire core loses heat to the mantle.

Last year Xiaodong Song and Paul Richards of Lamont-Doherty Earth Observatory in Palisades, N.Y., analyzed travel times of waves generated from South Atlantic earthquakes and recorded over a period of 30 years by a seismographic station in Alaska. They found that the time it takes these waves to pass through the Earth, including the inner core, gradually decreased by three-tenths of a second between the 1960s and the 1990s.

The complex explanation for this, says Creager, is that the solid inner core is anisotropic: its iron crystals are aligned in such a way that they produce a grain like that of wood. Seismic waves flow swiftly with the grain, but slowly against the grain.

Waves traveling roughly parallel to the polar axis on which the Earth spins move about 3 percent faster than those traveling perpendicular to the axis. The fastest direction, however, seems to be tilted about 10 degrees from the spin axis. Song and Richards reasoned that if the inner core rotates faster than the mantle by 1 degree a year, the waves traveling from the South Atlantic to Alaska were more closely aligned with the grain of the inner core during the 1990s than during the 1960s, opening up a faster travel pathway.

The Lamont-Doherty researchers assumed that the alignment of the crystals is the same throughout the inner core. In contrast, Creager, studied waves generated by three earthquakes in the South Atlantic in 1991 and recorded by an array of seismometers in Alaska. This allowed him to take a snapshot of the inner core and produce a detailed map showing a substantial change in speed as the waves traveled across a region of only 300 miles.

Because of this “dramatic” change in speed over such a short distance, says Creager, the inner core does not have to rotate very far to cause a three-tenths of a second change in travel time. He estimates that the inner core is rotating with respect to the mantle at a rate that is four times slower than that calculated by the Lamont-Doherty team.

At the current pace of rotation, Creager theorizes, it would take more than 1,000 years for the inner core to make one compete revolution with respect to the mantle and crust. By comparison, Song and Richards estimated that the inner core has made more than a quarter of a complete revolution just since the beginning of this century.

“Though we do not know what causes the iron crystals to align,” says Creager, “new clues are being revealed every year.” For example, he cites the recent discovery that crystals in the western hemisphere of the inner core appear to be aligned in a different fashion from those in the eastern hemisphere, and that the formations change over a region as small as a few hundred miles. This may be caused by convection within the inner core.

“The key observation is that something deep within the Earth is changing on the scale of human lifetimes,” says Creager. That, he notes, “is something new to seismologists.”

###
Creager can be reached at (206) 685-2803, or kcc@geophys.washington.edu
<!—at end of each paragraph insert

—>

First it was the Chinese, then the Egyptians who more than 3,000 years ago began studying and predicting the weather. Then in the 16th and 17th centuries meteorology became a science with the invention of instruments to measure the elements. Now a supercomputer is ushering in a new era of high-precision local weather forecasting.

The 91探花 has just switched on the latest version of its weather forecasting system, the first in the world to diagnose and forecast local weather on a scale of a few thousand yards. Already, says Clifford Mass, 91探花atmospheric sciences professor who has spearheaded the system, the MM5’s results are proving to be “dramatic.”

In fact the system has improved the ability to diagnose and forecast local weather so greatly that the National Weather Service in Seattle now has a computer work station dedicated to the MM5 output.

This is the latest development in a forecasting sea change that began last year when Mass helped organize a consortum of eight local, state and federal agencies, including the 91探花and the weather service, to purchase a powerful Sun Microsystems UltraSparc multiprocessor. Using advanced weather forecasting software, Mass and 91探花research meteorologist Mark Albright, were able to begin forecasting the weather in exquisite detail.

The software was able to use weather service data to simulate the evolution of the atmosphere over the Northwest by solving a series of complex equations every 12 kilometers (7.5 miles). Such a computer simulation pictures the atmosphere in terms of a three-dimensional grid, with each grid point representing a location where a weather calculation is made. The closer the grid points, the more detailed the weather forecast.

But in order to reduce the grid points even further, more computing power was essential.

Recently Sun Microsystems donated new processor chips to the project, speeding up the MM5 system 1 1/2 times, and allowing calculations every four kilometers (2.4 miles). This is by far the most detailed view of Northwest weather ever, Mass says.

The souped-up MM5’s four-kilometer portrait covers an area stretching from the Columbia River on the coast of Washington to the southern part of Vancouver Island, over the crest of the Cascade Mountains to the eastern slopes, then down to the Columbia Gorge on the Oregon border. In addition there are 12-kilometer and 36-kilometer (22.4 miles) grids over much larger areas. The forecasts are issued twice a day for the following 48 hours.

For the first time, says Mass, the computer is able to picture the rises and slopes of the region’s topography so accurately that it “sees” the effects of Mount Rainier, including the rain showers on one side of the mountain and the rainshadow on the other. It is also able to calculate wind directions with considerable accuracy.

In time, the system might also include forecasting the amount of water available to a region. That’s because Kenneth Westrick, a 91探花graduate student, is using the MM5 data to forecast river and stream flow for the Snoqualmie Basin, an important 602-square- mile watershed stretching west from the Cascades. Westrick is taking different measurements from the MM5 forecasting system, from winds to precipitation, and coupling them to an advanced hydrological computer model created by Dennis Lettenmaier, a 91探花civil engineering professor, and his students.

Forecasters have lacked precipitation data for the region because of the paucity of rain gauges and other observations in the mountains. But by using the MM5 meteorological data, the effects of climate and land-use change can be explored.

Another important use of the MM5 system, possibly within a year, will be its coupling to regional air-quality monitoring systems to forecast levels of ozone and pollutants in the atmosphere.

Mass does not see the MM5 narrowing its focus beyond four kilometers in the near future. Because of the absence of accurate meterological data from the North Pacific there is debate about the value of high-resolution forecasting systems. “Some say we shouldn’t go to high resolution but instead to an ensemble of lower-resolution forecasts,” says Mass.

If, for example, northwest winds from the Pacific are forecast as coming from the southwest, he says, “all the resolution in the world is not going to help you.”

### Contact Mass at (206) 685-0910, or cliff@atmos.washington.edu

<!—at end of each paragraph insert

—>

Stumps of long-dead western red cedar trees are revealing new details of a cataclysmic earthquake along North America’s west coast more than 100 years before the arrival of the first European occupants.

Two 91探花 researchers believe that evidence in the dead wood confirms that in the year 1700 a great earthquake struck the Pacific Northwest coast and set off a tsunami, a train of massive ocean waves, that flooded coastal Japan.

The scientists are reporting in tomorrow’s magazine (Oct. 30) that they have dated the demise of six trees, along 60 miles of the Washington coast, by “reading” the annual ring patterns in the trunks and roots of the stumps. They found that each of the trees produced its final ring in the 1699 growing season. No further rings were evident, indicating that the trees were dead by the spring of 1700.

“We are saying this huge earthquake really happened,” says David Yamaguchi, a 91探花dendrochronologist, or tree-ring analyst. Last year Japanese scientists reported that a tsunami that hit Honshu island on January 27, 1700, was probably caused by an earthquake on the Cascadia subduction zone, a 600-mile coastal fault stretching from British Columbia to northern California.

Based on the size of the tsunami, the Japanese researchers estimated the earthquake at magnitude 9, even though no Cascadia fault earthquake of magnitude 5 or above has ever been recorded by seismologists. The Nature article concludes that the tree dates “mean that the northwestern United States and adjacent Canada are plausibly subject to earthquakes of magnitude 9.”

The second author of the paper, Brian Atwater of the and an affiliate 91探花professor, says the new dates clinch the argument that massive earthquakes can occur where the Juan de Fuca plate, an Oregon-sized slab of crust, collides with a large block of continental crust called the North America plate. The Cascadia fault forms the boundary between the two plates.

Over the past decade, Atwater and other researchers have discovered geologic evidence of repeated magnitude 8 or larger earthquakes along the Cascadia fault. However, the size of the 1700 earthquake remains a subject of much debate, which the tree-ring dates do not resolve, says Atwater. Some scientists have proposed a ceiling of magnitude 8; others have suggested a maximum magnitude of 9.5.

Only a handful of magnitude 9 earthquakes have occurred globally this century. The largest earthquake in the Pacific Northwest in historic times was a magnitude 7.4 in the north Cascade mountains in 1872. This was not on the Cascadia fault.

Yamaguchi first “read” the cedar stumps to show that a great earthquake happened some time after 1690. 91探花researcher Minze Stuiver then pinned the earthquake to between 1695 and 1710 with precise radiocarbon dating. This led the Japanese scientists to propose the Cascadia fault as the likely origin for the 1700 tsunami.

To test the Japanese theory, the 91探花researchers dug up the roots of a dozen cedar stumps from the Copalis River south to the Columbia River. In half of these stumps, the dating was inconclusive, but in six they found evidence that the trees had died before the start of the 1700 growing season.

###

Contact David Yamaguchi at (206) 616-7414, or at yamaguch@u.washington.edu
Contact Brian Atwater at (206) 553-2927, or atwater@u.washington.edu
Graphics files are available on the World Wide Web at ftp:\\ftp.geophys.washington.edu/pub/out/tree/
<!—at end of each paragraph insert

—>

It looks like El Ni帽o, it feels like El Ni帽o, and if you are watching fish stocks, reservoir levels or farm production, you would say it is El Ni帽o. But it isn’t.

Researchers at the 91探花 are describing in two recent research papers what they call a decades-long climate shift in the Pacific Ocean that seems to explain many of the changing environmental patterns seen across North America, and particularly in the Pacific Northwest, since the late 1970s.

The scientists are calling this climatic phenomenon the PDO, for Pacific decadal oscillation. And, they say, its current positive cycle helps to explain why U.S. West Coast ocean temperatures have been warmer than average, why winters have been wetter than usual in the South, and why Alaska salmon harvests have been at historic highs, while there have been record declines along the West Coast.

El Ni帽o, it appears, is only one small — albeit exaggerated — phase of this cycle, says David Battisti, 91探花atmospheric sciences associate professor, who was the first to show why El Ni帽o recurs on an average of every four years. He describes this latest discovery as an index of sea-surface temperatures in the North Pacific, “which my guess also involves the tropics.” Says Battisti: “This phenomenon explains much about what is happening in regional climate change. And if we could predict the PDO, we would have much more reliable forecasts.”

However, says Nate Mantua, a 91探花research associate, scientists probably will not have the ability to begin making accurate forecasts for at least another five years. A PDO prediction system, he says, would allow long-term planning in such areas as fisheries, water supplies, agriculture and energy production.

“The science right now is more like our understanding of El Ni帽o 15 to 20 years ago,” says Mantua. But when a PDO forecast is developed, he says, it will become an important measure of climate across North America.

The discovery of the PDO has been something of a scientific detective story. Using high-speed computers, researchers combed the past century’s meteorological records to see if they could spot any recurring patterns of climate change. In more recent decades, El Ni帽o quickly emerged as the dominant recurring pattern of year-to-year climate variability on the planet. But when records were studied back to 1900, with the focus on the region north of Hawaii in the Pacific basin, the PDO revealed itself with positive and negative phases lasting from 10 to 30 years

With a few interruptions, researchers found that since 1977 the PDO has been in a positive phase with cool air in the Southeastern U.S., and a tendency to dry weather over the Columbia Basin and the Great Lakes. In the Northwest, winters have been largely warm and dry, water levels have been down because there have been fewer storms than normal, and snow packs have been low. In the previous negative phase of the PDO, lasting from 1947 to 1976, the Northwest’s water supplies were an average of 20 percent higher than between the 1920s and the 1940s, with more precipitation and higher snow packs.

Evidence also suggests that many populations of Pacific salmon are influenced by changes in marine climate. This could explain why in the last negative phase of the PDO, when coastal ocean temperatures were cooler, coho and chinook salmon were in abundance off the coasts of Washington, Oregon and California, but Alaska’s stocks were greatly depleted. Since the 1970s, warmer coastal waters have reversed these conditions. However, the 91探花researchers say, the present positive phase of the PDO should be expected to reverse within a decade, at which time favorable ocean conditions should return for West Coast salmon.

Many of these climate changes are felt across North America because of wave patterns — like ripples in a stream — in the atmosphere, which is directly affected by changes of temperature in Pacific Ocean currents. But the phenomenon is particularly evident in the Northwest because of a feature in the wind field called the Aleutian low, which directs atmospheric patterns across the region.

One of the puzzles of the PDO, says Mantua, is whether it acts as a restraint on El Ni帽o, or whether it is a long-term response to the phenomenon. Mantua says he prefers the argument that the PDO is a slower change in the climate system of the oceans and atmosphere over the entire Pacific basin which influences how El Ni帽o develops.

One frustrating aspect of attempting to forecast the PDO is that it develops over such a long period that a negative or a positive phase can have passed before researchers even discover it. “We can recognize the phenomenon, but we can’t say what phase we’re in at the time,” says Battisti. “But that’s only because we don’t yet fully understand it. After all, it has only been in recent years that we’ve recognized it even exists.”

###
To find out what the PDO forecast could be for your region, call Battisti at (206) 543- 2019, or at david@atmos.washington.edu or call Mantua at (206) 616-5347, or at mantua@atmos.washington.edu.
Battitsti’s paper, whose authors include 91探花professor of atmospheric sciences John Wallace and graduate student Yuan Zhang, appeared in Journal of Climate.
Mantua’s paper, whose authors include 91探花quantitive biologist Steven Hare (who, with Zhang, discovered the PDO, and who coined the term), 91探花professor of fisheries Robert Francis, Wallace and Zhang, appeared in the Bulletin of the American Meteorological Society.

They spent their summer working in the lab instead of enjoying the sunshine, studying everything from cloning and protective coatings to mosquito control. On Friday, they will get their reward.

At a reception at the 91探花’s Kane Hall, 50 undergraduates will be honored for their summer research sponsored by the Washington Space Grant Consortium. The students will present posters detailing their discoveries, and in turn will be presented with certificates by Provost Lee Huntsman, who will deliver the keynote address.

The ceremony will also honor 17 incoming freshmen who have been awarded Space Grant scholarships to study at the UW. The undergraduate awards, which are renewable for up to four years, will enable the students to study math, science or engineering. Two graduate students sponsored by the program also will be honored.

The summer research program has given practical science experience to 176 undergraduates since it began in 1993, making it a model for 91探花President Richard McCormick’s goal to involve more undergraduates in faculty research projects. This year’s program was supported by $80,000 in grants from the NASA Space Grant Program at the UW, the Mary Gates Foundation, and from faculty research grants.

The funding supported 48 91探花undergraduates, half of them Space Grant scholarship students, and two students from Washington State University and Harvard. Each student was employed up to 40 hours a week by a 91探花faculty member doing research in science, engineering or math.

Thus Michael Brown, who is chairman of the geophysics department, employed Marcus Collins of Woodinville (who has already presented his research at the fall meeting of the American Geophysical Union) to assist in his research on the Earth’s mantle; chemistry professor Martin Gouterman employed Myrna Vitavosic, a 15-year-old early- entry student, to assist him with his study on pressure-sensitive paint; and Joan Sanders, an assistant professor of bioengineering, was helped on her study of mechanical stress by another early-entry student, Sam Bishop, 15.

Perhaps the most unusual research project was that participated in by Anne Prather, a post-baccalaureate researcher under associate botany professor Elizabeth Van Volkenburgh, whose lab is studying the physiology of leaf growth and development. Prather’s research assistant was Anna Schneider, a senior from Seattle, who is blind.

Prather, who is legally blind, spent much of the summer course teaching Schneider basic lab techniques for a blind person: handling delicate equipment, identifying plant anatomy by feel, and learning the safe and effective way of transferring liquids. Says Schneider, who is studying cellular and molecular biology: “I always wanted to do lab work, but it was never possible until now.”

These two students’ hard work give support to Space Grant director Janice Decosmo’s view that “this summer program is not just financial aid–it is all about hands-on experience helping to enhance classroom work.”

The awards ceremony is on Oct. 3 in the Walker-Ames Room, Kane Hall, on the 91探花 campus, from 3 p.m. to 5 p.m. Decosmo can be reached at (206) 685-8542, or janice@geophys.washington.edu

### <!—at end of each paragraph insert

—>

A new form of matter, clusters of atoms, has been oberved in recent years behaving in curious ways. Now research indicates that clusters have another, previously unsuspected property: they can melt at different temperatures from “solid” matter.

An experiment described in tomorrow’s Science (Sept. 12) paints an exotic portrait of certain substances seemingly confounding nature by existing as a liquid, instead of a solid, at room temperature.

George Bertsch, a theoretical physicist at the 91探花, describes how the experiment with clusters of sodium atoms found that the atoms did not follow sodium’s normal pattern, melting at 97.8 degrees Centigrade (208 degrees Fahrenheit). Instead, the small clusters of atoms melted at minus 6 degrees Centigrade (21 degrees Fahrenheit), well below room temperature.

The discovery was the work of Hellmut Haberland at the University of Freiburg in Germany. Bertsch, who has been following the field of cluster research for the past decade, writes that as a result of the experiment, scientists are now challenged “to understand what happens to the liquid and solid phases in small particles.”

European researchers are working on a number of practical applications for the cluster phenomenon. Attempts are being made to produce thin films of silicon clusters that would process signals carried by light. Others are researching the use of clusters to improve the magnetic recording of data. And Haberland has been reported to have produced clusters of the element molybdenum that will even stick to Teflon.

Clusters have been called a new type of matter, says Bertsch, because they appear to be a bridge between atoms and the world of normal size, and have strange magnetic, electrical and optical properties. What is particularly curious, he says, is that the properties of the clusters depend on the number of atoms they contain.

Bertsch notes that most clusters are very unstable collections — “they touch a wall and they are gone.” But a decade ago it was discovered that certain clusters contain “magic numbers” of atoms that make them particularly stable. These numbers begin with just two atoms, and continue through eight, 20 and 40 and into the hundreds of atoms. The German researcher used magic-number clusters of 139 sodium atoms. The melting point was observed by forming condensation ‘droplets’, rather like hot steam hitting a cold window, and passing the condensate through a mass spectrometer and finally an electric field.

Bertsch concedes that the research is controversial, and there are physicists who insist there can only be one melting temperature for each of the 92 natural elements. But, he says, “as scientists we have to look at the evidence.” What’s more, he believes there is evidence that the same phenomenon that the German researcher demonstrated with sodium, also exists with atomic clusters of both tin and lead.

The 91探花scientist is hesitant to attempt an explanation of what is causing the lower melting point of these elements. However, he notes, it has been suggested that there is a relation to a theory known as surface melting: when a substance reaches melting temperature, only a small surface layer melts immediately. “As solid sodium reaches melting temperature, a small layer of liquid might form on top of the solid,” he says. “In a cluster, all you would have is this outer, liquid layer.”

It could be said, says Bertsch, that this new type of matter is “practically all surface.” If there is already something strange happening at the surface of certain elements, “then you accentuate that behavior when you create clusters.”

###
Contact Bertsch at (206) 543-2895, or at bertsch@phys.washington.edu.

A new form of matter, clusters of atoms, has been oberved in recent years behaving in curious ways. Now research indicates that clusters have another, previously unsuspected property: they can melt at different temperatures from “solid” matter.

An experiment described in tomorrow’s Science (Sept. 12) paints an exotic portrait of certain substances seemingly confounding nature by existing as a liquid, instead of a solid, at room temperature.

George Bertsch, a theoretical physicist at the 91探花, describes how the experiment with clusters of sodium atoms found that the atoms did not follow sodium’s normal pattern, melting at 97.8 degrees Centigrade (208 degrees Fahrenheit). Instead, the small clusters of atoms melted at minus 6 degrees Centigrade (21 degrees Fahrenheit), well below room temperature.

The discovery was the work of Hellmut Haberland at the University of Freiburg in Germany. Bertsch, who has been following the field of cluster research for the past decade, writes that as a result of the experiment, scientists are now challenged “to understand what happens to the liquid and solid phases in small particles.”

European researchers are working on a number of practical applications for the cluster phenomenon. Attempts are being made to produce thin films of silicon clusters that would process signals carried by light. Others are researching the use of clusters to improve the magnetic recording of data. And Haberland has been reported to have produced clusters of the element molybdenum that will even stick to Teflon.

Clusters have been called a new type of matter, says Bertsch, because they appear to be a bridge between atoms and the world of normal size, and have strange magnetic, electrical and optical properties. What is particularly curious, he says, is that the properties of the clusters depend on the number of atoms they contain.

Bertsch notes that most clusters are very unstable collections — “they touch a wall and they are gone.” But a decade ago it was discovered that certain clusters contain “magic numbers” of atoms that make them particularly stable. These numbers begin with just two atoms, and continue through eight, 20 and 40 and into the hundreds of atoms. The German researcher used magic-number clusters of 139 sodium atoms. The melting point was observed by forming condensation ‘droplets’, rather like hot steam hitting a cold window, and passing the condensate through a mass spectrometer and finally an electric field.

Bertsch concedes that the research is controversial, and there are physicists who insist there can only be one melting temperature for each of the 92 natural elements. But, he says, “as scientists we have to look at the evidence.” What’s more, he believes there is evidence that the same phenomenon that the German researcher demonstrated with sodium, also exists with atomic clusters of both tin and lead.

The 91探花scientist is hesitant to attempt an explanation of what is causing the lower melting point of these elements. However, he notes, it has been suggested that there is a relation to a theory known as surface melting: when a substance reaches melting temperature, only a small surface layer melts immediately. “As solid sodium reaches melting temperature, a small layer of liquid might form on top of the solid,” he says. “In a cluster, all you would have is this outer, liquid layer.”

It could be said, says Bertsch, that this new type of matter is “practically all surface.” If there is already something strange happening at the surface of certain elements, “then you accentuate that behavior when you create clusters.”

###
Contact Bertsch at (206) 543-2895, or at bertsch@phys.washington.edu.