The research arm of Sweden's Defense Department has turned up what it speculates is evidence that the Soviet Union is testing a 'death ray' weapon to destroy satellites and missiles space.

The evidence involves the detection five times last year in the air over Sweden of mysterious radioisotopes that had no connection with nuclear weapons test in China ot the Soviet Union or with the airborne releases of radioactive contaminers from nuclear power plants anywhere in Scandinavia.

"As the observed events cannot be accounted for in terms of any known source," said a report this week in Science magazine. "the observations and speculation concerning charged particle beam experiments an interesting possibility."

The report in Science was signed by Dr. Lars-Erick De Geer, whom was described by the Swedish embassy as a Scientist with the National Defense Research Institute in Stockholm. The embassy said the institute comes directly under the Swedish Department of Defense.

The Particle-beam experiments alluded to in the Science report have long been discussed in documents and testimony given to Congress by the Pentagon, which worries that beams of electrons or protons could destroy missiles or satellites the same way "deathrays" destroyed space ships in old Buck Rogers comic Strips.

The Pentagon has suggested that the Soviets have tested models of a particle beam weapon at Semipalatinsk, where the Soviet Union conducts underground nuclear weapons test.

The detection last year of short-lived radioactive isotopes in the air over Sweden on five different occasions may be evidence of particle-beam test, the article said. Each time the isotopes were found, the prevailing winds were from the direction of the Soviet Union.

The isotopes were found in "unusual mixtures" in lata February, March, April, May and July of 1976. Most of the isotopes found on the five occasions were Neptunium-239 and Molybdenum-99, usually identified with the atmosphere debris from nuclear explosions.

China exploded what was described as a small nuclear device in the atmosphere on Jan. 23, 1976. This explosion "could not" be the source of the larger concentrations of the Neptunium and Molybdenum in Swedish airspace on any of the five occasions they were found, the report says.

The report says there were no atomic explosion underground in the Soviet Union that vented debris to the atmosphere on any of the five occasions. The report also rules out accidental releases from nuclear power plants in Sweden. Denmark or Finland.

"None of these reactors reported any airbone effluents during 1976 that could be correlated with the Neptunium and Molybdenum detected," the report said.

Ruling out these possibilities, the report speculates that the isotopes could have come from test of a particle-beam weapon. The report discusses the possibility that a "nuclear explosive generator is being developed as the power source to drive the accelerator producing the charged particle beam.

"Steel segment used for the construction of two large spheres that be part of such generator," the report goes on "have been observed at Semipalatinsk from reconnaissance satellite, along with large releases of hydrogen at some altitude. Tests have been observed on seven occasions since November, 1975 that may be related to such a device."

The possible existence of a particle-beam weapon has been met with widespread skepticism by U.S. scientists, whose reaction ranges from disbelief to doubt that such a weapon could exist any time in the next 20 years. The reason they give for their skepticism is that a power source for such a weapon would have to be enormous and produce enough initial power to electrifiy a small city.

The reason the Pentagon worries about such weapon is that there would be little defense it. Once started, a stream of electrons of protons could be continuous because it would never have to be reloaded. Defense might be impossible because electrons and protons would be able to penetrate any missile or satellite devised.