pho·to·e·mis·sion 
(fō′tō-ĭ-mĭshən)
(fō′tō-ĭ-mĭshən)n.
Emission of photoelectrons, especially from metallic surfaces.
- keep an eye on
- keep an eye out
- keep a/one's weather eye open
- keep a stiff upper lip
- keep at
- keep a weather eye open
- keep chin up
- keep company
- keep company
- keep down
- keep end up
- keeper
- keep eyes open
- keep eyes peeled
- keep fingers crossed
- keep head
- keep/hold (one's) peace
- keeping
- keep/know (one's) place
- keep kosher
- keep nose clean
- keep nose to the grindstone
- keep off
- keep (one's) chin up
- keep one's chin up