I’d cite studies and research and books I’ve read on the power of napping, but why? If you have the afternoon “foggies” and are having a hard time concentrating and being motivated to work, take a 15 minute break, find a tree outside (if it’s nice) or a quiet closet somewhere, or go to your car, and take a nap. Preferably with your legs elevated.
It’d be helpful if you had your boss’s permission, especially if you work in an office, but I guarantee you you will be more focused and productive the rest of the afternoon.
Or, you can be proactive about this and do it over your lunch break if you have a conscience (or employer) issue with doing this during work hours. You might even get to use your couch or a bed as an added bonus.
(And yes, that’s my adorable toddler daughter. She’ll probably hate me for this someday)