What is the ruling on a married man touching a divorced woman who works with him in a closed space, and who refuses to wear the niqab?

What you have mentioned about being alone with a woman and touching her body, and what led to temptation and the enticement of the self to commit haram, are all forbidden matters. The Prophet, peace and blessings be upon him, forbade being alone with a non-mahram woman, and severe warnings have been established regarding touching a woman who is not permissible for a man. What you fell into is considered zina (fornication/adultery) in the broader sense, because the eye commits zina by looking, and the ear by listening, and so on. The correct course of action is to separate this woman from working with you, or to marry her if you wish to amend her behavior.