phosphorescence vs radiation

phosphorescence

noun
  • The emission of light without any perceptible heat; the quality of being phosphorescent. 

radiation

noun
  • The transfer of energy via radiation. 

  • The shooting forth of anything from a point or surface, like diverging rays of light. 

  • The process of radiating waves or particles. 

  • A rapid diversification of an ancestral species into many new forms. 

  • Radioactive energy. 

How often have the words phosphorescence and radiation occurred in a corpus of books? (source: Google Ngram Viewer )