Does divorce take effect if it crosses the husband's mind and he utters the word "divorce" without mentioning any condition, while the wife is not present?

As for the vow, it is an adjuratory vow which requires an expiation for breaking an oath, and if he fulfills it, there is no harm.

As for obsessive-compulsive disorder, the questioner should reject these whispers and pay no attention to them. He should seek help and refuge with Allah Almighty from the evil of the whispering devil (al-waswas al-khannas), consistently recite the two surahs of refuge (al-Mu'awwidhatayn), frequently recite the Qur'an, and persistently engage in the remembrance of Allah Almighty.

As for his utterance of the word "divorce" in this manner, without attributing it to his wife, it does not constitute a divorce. He is not accountable for anything that crossed his mind by way of prior thoughts before uttering the aforementioned word, for Allah does not hold a servant accountable for what passes through their mind. Furthermore, if the whispers of waswas reach a level that overwhelms someone, their divorce does not take effect.