Does a divorce occur if a man swore an oath by divorce that he would not intentionally engage in online conversations with girls, and then he opened a previous chat room belonging to someone else to view a picture of a girl, while he does not specifically recall the wording of his oath?

It appears from the question that the motivation for the oath was to avoid the unlawful. Therefore, by entering the chat and looking at the girl's picture, the oath is broken, whether the oath was concerning entering the chat or engaging in that action, considering the intention behind the oath. Scholars have differed on whether this constitutes a divorce or requires an expiation for a broken oath. The majority of scholars hold that divorce occurs, while Ibn Taymiyyah held that it requires an expiation for an oath. If the action was committed out of forgetfulness of the oath, then the oath is not broken. It is advised to avoid situations that lead to temptation and to be diligent in enjoining good and forbidding evil.