He was taken into custody Friday, partly because authorities at the school had contacted him in the past after he was reported to be acting suspiciously and touching female students, said Cmdr. Barry Aninag of the Irvine Police Department.
The assault occurred Thursday night, Aninag said.
The 18-year-old woman had met Alireza Hashemi that day on campus, but did not know him before, Aninag said.
The two were having a conversation, Aninag said, when Hashemi forced the woman into the back seat of his vehicle.
"She was able to escape from his control," Aninag said.
The woman ran away and reported the attack to police, he said.
The woman's description matched that of Hashemi, who had been stopped by authorities before when women on campus had been touched inappropriately, Aninag said.
No arrest was made in those incidents, he said.
Hashemi was being held at Men's Central Jail on suspicion of sexual assault.