You might want to think twice about doing this. There are a number of articles on the web about Googlebot and the AdSense bot, including this one, which says:
If you serve different pages to Googlebot and Mediabot then Google might ban your web site because you use cloaking on your web site. Cloaking means that you're showing different pages to users than to search engines.
As Mediabot analyzes the web pages you serve for your visitors it's easy for Google to find out if you present extra pages for Googlebot. If you do something special for Googlebot then Google knows that you're cloaking.
Check the AdSense Terms and Conditions very carefully before risking getting banned.