The Gifted Refugees

History's greatest brain drain occurred during the 1930s, when thousands of intellectuals fled Nazi Germany and took refuge in other countries. What Germany lost and other nations gained was re-emphasized last week when the latest Nobel prizes in science went to two refugees from Hitler: Dennis Gabor, who won the 1971 prize in physics for his invention of holography, and Gerhard Herzberg, who earned the laurels in chemistry for his pioneering work in molecular spectroscopy.

Gabor got the idea that led to his prize one day in 1947 while he was waiting his turn at a tennis court in Rugby, England. Out of a sudden flash of insight, he created a system of lensless, three-dimensional photography that became known as holography (from the Greek words for "whole" and "writing").

Optical Mismatch. Gabor's technique was elegantly simple. He filtered out all but the green light emitted by a powerful mercury arc lamp, producing a beam of light waves of a single frequency (ordinary sunlight is composed of many different frequencies). Then he aimed the beam at an object placed in front of a photographic plate. The unobstructed part of the light beam hit the plate directly. Light waves reflected from the object's irregular surface also reached the photographic plate. But because they had bounced off different parts of the object, they arrived at the plate out of phase in varying degrees with the original unreflected beam--that is, the crests and troughs of the reflected light waves no longer matched up with those of the unobstructed light.

If the crests of some of the mismatched waves happened to coincide, the waves strengthened one another and produced a bright spot on the film. But if the crests of one wave lined up with the troughs of another, the waves tended to cancel each other out and barely registered on the film. The result was a hologram, a pattern of light and dark spots that while formless to the eye, encoded all the characteristics of the object. When Gabor shined the same single-frequency light through the film, the result was a three-dimensional image of the object.

Practical Reality. Gabor's holograms were crude because his beam of filtered green light was not intense enough to produce a clear image. But in 1963, after the invention of the laser made available powerful single-frequency light waves that were precisely in phase. University of Michigan Physicists Emmett Leith and Juris Uptanieks made Gabor's holography a practical reality. Already used in displays, material testing, medical diagnosis and computer memory banks, holography has potential for 3-D movies and, some day, for television.

While Herzberg's work is not used in such everyday applications, it is extremely important scientifically. By studying the distinctive characteristics of the electromagnetic radiation that molecules emit or absorb, Herzberg has been able to describe their structure, geometry and energy levels with extraordinary precision. In fact, his spectroscopic "fingerprinting" is so accurate that it has been used to identify free-floating molecules in distant space. More recently, Herzberg, a scientist working for Canada's National Research Council, has conducted important investigations into so-called "free radicals"--short-lived molecular fragments whose activities are crucial to many chemical reactions, including those of life itself.

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