A federal judge today sentenced a former State Department official to 27 months in prison and three years of supervised probation for illegally exporting weapons to the Dominican Republic and accepting payments for them.

George R. Mitchell, 43, was released on bond pending appeal of his conviction in U.S. District Court in Baltimore.

Prosecutors had sought a stiffer penalty against Mitchell, but Judge Marvin J. Garbis acknowledged that Mitchell had risked his life while working as a security officer with the State Department, including one incident in which he was credited with saving the life of a Turkish ambassador during an assassination attempt.

Garbis said he considered "extraordinary circumstances" surrounding Mitchell's work history with the State Department in imposing a lesser sentence.

Herbert R. Rubenstein, the defense lawyer, had asked that the judge not impose a prison sentence at all, and instead place Mitchell under house arrest, which would allow him to work.

The judge ruled, however, that the nature of the crime required a prison term.

After a two-week trial, a federal jury convicted Mitchell on Sept. 20 of buying guns and selling them and vehicles illegally in the Dominican Republic.

Assistant U.S. Attorney Stuart A. Berman said Mitchell earned more than $30,000 for the deals, but Garbis said he could determine profits of only $11,000.