Old Rikenon on a Nikon D5000?

See the link http://cgi.ebay.com/...f5de2#shId

Will my 25 years old 52ø Rikenon XR 1:2 50mm L lens, work on the new Nikon d5000 DSLR, using this adapter

Near as I can tell this is a purely mechanical adapter. So yes your lens will mount, you may encounter problems with infinity focus. You will be restricted to shooting in manual mode only.

Honestly, knowing those old lenses and considering the price of this adapter I think you'd be better of savign for a 50mm f1.8 AF which will still be manual focus but at least it will work in all camera modes.

Possibly, but no auto nor exposure measuring facilities - don't spend any money without seeing by demonstration that it works. Really best to get a lens intended for Nikon.