The list of states in contention for the scientific plum of the decade, a $6 billion federally financed atom smasher, was pared to eight yesterday by the National Academies of Sciences and Engineering.

Texas, Arizona, Colorado, Tennessee, New York, Illinois, Michigan and North Carolina made the first cut on the basis of technical merit, according to a report released a day early after several members of Congress jumped the gun and announced the finalists.

Twenty-five states entered the fevered competition earlier this year for the massive superconducting supercollider, a 53-mile underground tunnel that would be 20 times more powerful than any atom smasher now in existence. The project, endorsed by President Reagan, is expected to bring its host state 3,000 jobs, an annual payroll of $270 million and a leg up in attracting high-tech industry.

Several states spent millions of dollars preparing their applications. Several more led pilgrimages to Washington, bearing videocassettes, trinkets, platters of native cuisine and pamphlets describing their superior academic institutions, climates and life styles.

Congress, however, has not yet agreed to finance the massive collider, which physicists hope will shed new light on the structure and behavior of matter. Appropriations this year were $25 million for preparation work, $10 million less than the Energy Department's request.

Proponents fear that congressional enthusiasm for the project will drop significantly as the list of contenders shrinks. Among the states that didn't make the finals was California, with 45 votes in the House.

The academies' report went to Energy Secretary John S. Herrington, who is scheduled to announce his choice in July.

The 21-member panel examined 35 sites (some states submitted as many as four) for technical merit, including suitable geology for tunneling and access to adequate highway and air transportation.

The report does not explain why certain sites were rejected. In general, it said, some "displayed unfavorable geological conditions" and others were unable to meet "regional resources criteria," a catchall phrase that includes everything from skilled construction labor to job opportunities for scientists' families.

The states that failed to make the cut were Alaska, California, Florida, Idaho, Kansas, Louisiana, Mississippi, Montana, Nevada, New Mexico, Ohio, Oklahoma, Oregon, South Dakota, Utah, Washington and Wyoming.