Lol; vapour cooling of the air.I don't know how you would go about condensing Nitrogen; but to do it you will need to do the same as if you were trying to cool the processor - and so using Nitrogen you'd be wasting time for cooling and adding a useless layer
You'd have to use Water - put it into an area around the processor which is depressurised as much as you want it - that way the water boils but has to take the energy to do so from around it. The lower the pressure the faster the water boils and the more energy is required from around it. If say this was around a heatsink it would take the energy from the metal which then takes it from the processor.