You are wrong in so many ways at the same time, it is not clear where to start
However, there is at least one place where the answer is obvious:
Also, is it possible that Mass spectrometry which cannot initiate fission (thank you DevaDevil) could initiate a decay (emission of a particle not fission) of O or N into one of its isotope? If that's possible, is it possible that the particle emitted through that decay be one of the noble gas?
"Particle emitted during decay" as you put it can be only smaller than the original nucleus. As original nucleus has 7 protons (nitrogen) and 8 protons (oxygen), they can only emit particles that have 1, 2, 3, 4, 5 and 6 protons - these are nuclei of hydrogen, helium, lithium, beryllium, boron and carbon - neither of the is a noble gas of the large mass.
It doesn't mean such things happen - they don't.
You were already suggested to learn a little bit about elements, isotopes, nuclei, neutrons and protons - if you will try to at least read wikipedia articles and understand the very basic info about how the matter is build, you will see why your ideas are completely off.