How do I neutralize dead rat odor
You can deal with the odor in several ways. You can use an air cleaner with an absorbent filter, neutralizes the odor, or add a new, more desirable odor to mask or cover up the bad odor. Use a neutralizer like Epoleon for this and read on from www.techletter.com/Archive/Technical%20Articles/smellofdeath.html.
Hopefully you have removed the dead rat, because that is the best answer. Also the age old thing is to get lime a garden supply store and put that down.