It is natural to experience feelings of abandonment which can trigger both anger and sadness when a spouse dies. Mourning and sadness allows us to gradually let go, as to some extent we experience the person with us in some way. When you begin to date, you are beginning to move on towards the possibility of a new family constellation, a new possibility for partnership. This is an experience of greater separation, as you know your wife will never share in this new situation. This does not make you a traitor.
Anger is an emotion which is sometimes helpful in separating.
Perhaps there are things that were left unsaid between you. Certainly there was much that was unfinished. Reflect on what words you would give your anger if you could speak to your wife now. Feelings are not logical. If these feelings continue to be uncomfortable for you, consider consulting with a counselor individually who will help you acknowledge and work through your anger and your guilt.