Ian Somerhalder Ambushed By Singing Fan 'You Make Me Feel Like a Natural Woman!'

4/29/2014 12:15 AM PDT

"Vampire Diaries" star Ian Somerhalder can make a girl orgasm just by touching her -- at least that's the way it looks in this video, showing a USC student spontaneously bursting into "Natural Woman" last Tuesday ... as soon as she holds his hand.

Ian had just finished an Earth Day talk at the school -- he's a big conservationist -- when student Shelby Miguel dropped the Aretha assault during a meet-and-greet ... out of nowhere.

It's pretty damn ballsy -- not to mention awkward as hell -- but check out the video ... she's got a great voice.