Isaac F. Silvera, an American experimental physicist at the University of Amsterdam, Holland, will join Harvard's Physics Department next fall, bringing to an end a search that has lasted interminently for more than five years.

The department offered tenure to at least five other experimental physicists before Silvera accepted, Michael Tinkham, Rumford Professor of Physics, said yesterday.

It is often difficult to hire established experimental physicists, who may be reluctant to leave their accustomed laboratories and sources of support, Harvard physicists noted. "Harvard is a great university but in terms of physics facilities, there's nothing we have that other universities wouldn't have," said Karl Strauch, who chaired the department last fall when Silvera's appointment was made.

A major reason for the department's success in hiring Silvera was his eagerness to return to America, Strauch said.

Silvera is best known for his low-temperature work with single atoms of hydrogen, which are normally found only in pairs. Research on hydrogen, the simplest element, often results in useful information about other elements.

Silvera did both his undergraduate and graduate work at the University of California at Berkeley, where he was a student of Tinkham's. Before he went to Amsterdam, he worked on basic research at a laboratory operated by the aerospace corporation Rockwell International.