Alexei and Angela Mihelson, above, stand under their chupah waiting for their ceremony to begin. At right, Rabbi Joseph Mishalovin marries Lena and Oleg Molonitkov. They were among 20 Soviet couples who repeated their marriage vows during a group wedding for Jewish immigrants in Los Angeles this week and savored the religious freedom denied them under Communist rule in their former homeland. A few couples exchanged vows for the first time, but most had been married in civil ceremonies in the Soviet Union, where the government had barred Jewish religious services. The celebration, held on the lawn at the Westin Bonaventure, featured 20 chupahs --the traditional canopy symbolizing the Jewish home--set up under the stars.