"experiment" indicates that you're talking about just one. you could say, "I will do an experiment." "experimentation" means that you're talking more about experimentation in general and could refer to more than one experiment. for example, "I will do experimentation." notice that you do not put an article like "an" before experimentation. does that answer your question?

"Experiment" is countable: "They conducted an experiment on rats." "Experimentation" is uncountable: "They conducted an experimentation on rats." that's false you can't use an in this case. "Experiment" refers to a particular test. "Experimentation" is the act of doing experiments. Ex: Some people believe that experiments on animals should be banned. Experimentation on animals should be banned.