As a Peace Corps volunteer, Osmun worked at a center that provides support to people affected by the AIDS virus. He told the court in June that he helped supervise children and was left alone with them for 10 to 30 minutes and recognized that as an opportunity to abuse them.
Osmun admitted that he engaged in acts with one of his victims twice per week for about five months.
Fein said Osmun had shown remorse, but he called the crimes "heinous" and read a letter from an official at the center who said the children were abused in the one place they could feel safe. She said the children are in counseling and staff were traumatized as well.
"These children have so little, but Jesse has taken the very fundamentals of their lives away," she wrote.
The Peace Corps has said it was made aware of the allegations after Osmun resigned in May 2011. The agency has condemned Osmun's actions as "reprehensible" and agreed to contribute $20,000 to a fund for the victims.
Peace Corps volunteers, who are provided with a living allowance and receive transition funds after they complete 27 months of service, provide hands-on assistance in areas including health education, information technology and environmental preservation. The Peace Corps has sent more than 200,000 Americans to serve in 139 countries.