I´m only slightly familiar with legal codes from the viking era, and dont have any sources at hand. But a death punishment would be vengeance rather than legal punishment. The Norse did not use a death penalty, and the harshest sentence would be to outlaw the offender, who could theoretically thereafter be killed without legal consequences.

It should also be noted that Norse laws were not applied in a modern sense, and whatever the laws on rape were, the future of a legal case (if any) would probably have more to do with the status of the families/clans of the involved parties.