A West German and two Americans, including a naval research scientist here, won Nobel Prizes in chemistry and physics yesterday. The chemistry award went to the Americans for inventing a method to determine the three-dimensional shape of molecules.

The physics prize, to a West German, was for his discovery of how electrons behave as they flow through a conductor in the form of electricity.

The chemistry prize went jointly to Herbert A. Hauptman, 68, a professor at the Medical Foundation of Buffalo, N.Y., and Jerome Karle, 67, a researcher at the U.S. Naval Research Laboratory here. The physics award was given to Klaus von Klitzing, 42, of the Max Planck Institute in Stuttgart.

Karle, who lives in Falls Church, was aboard a flight from Munich to Dulles airport when he learned over the plane's public address system that he had won a share of the cash prize of 1.8 million Swedish kronor, or about $225,000.

"We are honored to have flying with us today America's newest Nobel Prize winner, and he doesn't even know it," said the Pan Am pilot. The passengers applauded and crew members opened a bottle of champagne for Karle.

Karle's wife Isabella, a scientist who has won numerous prizes for applying the method worked out by her husband and Hauptman, learned of the award when she arrived at work yesterday morning at the Naval Research Lab. "I do the physical applications, he works with the theoretical," she said. "It makes a good team. Science requires both types."

At an airport news conference, Karle was asked if he had anticipated winning. "There are very few serious scientists who don't fantasize about it one time or another," Karle said. "I thought it might be possible. The fact that it has actually happened is a little bit new."

The awards, whose recipients are determined by the Royal Swedish Academy of Sciences, include a medal bearing the likeness of Alfred Nobel, the Swedish inventor who established the prizes under the terms of his will in 1896 and endowed them with his earnings from the invention of dynamite.

Karle and Hauptman won for creating a method to determine the three-dimensional structure of all but the biggest molecules. Knowing the detailed molecular structure of a chemical can be crucial in determining how it works, or in trying to make the substance artificially.

Knowledge of molecular structure is important in chemistry and all the fields in which chemistry plays a role, from gene engineering to materials research to drug research.

"The Nobel Prize for chemistry is all about changing the field of chemistry. And this work changed the field," said Nobel laureate William Lipscomb of Harvard University. He said that throughout the field, the so-called "direct method" of Karle and Hauptman is used 80 to 90 percent of the time that molecule structures are determined.

A few decades ago, it could take months or even years to decipher the atomic structure of a substance. "It used to be a PhD thesis to run a structure or two," Lipscomb said. But now, with the direct method run on a computer, "You don't even have to be a crystallographer to get a 3D model of something. I have a service here that determines structure that is run by graduate students. It takes only a day or two now."

In chemistry, substances act the way they do because of their structure. For example, hemoglobin in the blood can carry oxygen because it can fold over and hold an oxygen molecule inside it. When it arrives at its destination in the body, another molecule by its shape triggers the unfolding of the hemoglobin and release of the oxygen.

Because molecular shapes dominate chemical action in the world, it is crucial to determine them, to compare them, and to find the "active sites" which give molecules their power to act.

Determining molecular shape with what is called X-ray crystallography has been a continuous challenge throughout this century. In crystallography, X-ray beams are fired at a material that has been formed into crystals. The X-rays reflect off atoms within the crystals and produce a pattern of dots on photographic film.

The pattern corresponds to atoms' positions much as the pattern of light reflected by the mirrored balls in dance halls corresponds to the facets of the mirror.

The "direct method" is a mathematical system for using the intensity of the X-ray spots, together with other measurements, to reconstruct the placement of atoms in the crystal. This gives a three-dimensional shape for the molecule.

Such a shape can make clear, for example, where the "active" part of a drug is and be helpful in making new versions of it. In one case, the anticancer drug vincristine derived from plants, William Lipscomb said that chemists originally had worked out its structure incorrectly. When the direct method was used, the correct structure was determined -- and with the correct structure, the substance can be made artificially and more cheaply.

"It is almost impossible to give an example in the field of chemistry where this method is not being used," a Nobel judge said.

Von Klitzing was honored for discovering something called the "quantized Hall effect." This is a phenomenon that describes the detailed behavior of electrons that move through an electrical conductor under special conditions. When an ordinary wire conducts electricity, the wire serves as a kind of pipe through which electrons flow.

Von Klitzing's discovery is a refinement in the understanding of a phenomenon about electron flow discovered in 1879 by Edwin H. Hall, an American physicist.

Hall was studying the way in which electrons (in the form of electricity) flow through a flat metal strip placed in a magnetic field. If the lines of magnetic force cut up and down through the strip, some of the flowing electrons move to one edge, creating a small current that flows sideways while the main current flows from one end of the strip to the other.

This so-called Hall effect has been put to use in instruments that measure the strength of magnetic fields. The higher the "Hall current" from one edge to the other, the stronger the magnetic field.

Von Klitzing's contribution, made 101 years after Hall's discovery, was to show that if the metal strip is extremely thin and if the magnetic field is extremely strong, the rate at which the electrons pile up at one edge does not vary smoothly with smooth changes in the magnetic field. Instead the rate changes in a stepwise fashion.

In other words, the metal's resistance to the sideways Hall current diminishes in discrete steps, or quanta, even as the magnetic field increases smoothly.

"This is probably not the easiest thing to understand but as far as physicists are concerned, it was clearly Nobel caliber work," said Arthur Gossard, a physicist who has made related discoveries at Bell Labs in Murray Hill, N.J.

Gossard said von Klitzing's discovery would permit the development of more precise standards for measuring electrical resistance, which is expected to be used in microelectronics.